contents 1. monday, august 28 - ibs-conference · 2020-02-11 · 1 . manipulating relativistic...
TRANSCRIPT
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Contents
1. Monday, August 28
MOI1, Victor Malka, Manipulating Relativistic Electrons with Intense Laser Pulses ............................................................ 1
MOI2, Félicie Albert, Development and applications of betatron x-ray radiation for high energy density
science ........................................................................................................................................................................................................................ 2
MOI3, Ulrich Schramm, Electron and ion acceleration news from the novel Petawatt laser facility in Dresden . 3
MOI4, Tomonao Hosokai, Staging Laser Wakefield Acceleration Research aiming for Repeatable GeV-class
Accelerator ............................................................................................................................................................................................................... 4
MOI5, Seong Ku Lee, Development of 20-fs 4-PW laser for laser-plasma accelerators .................................................. 5
MOI6, Masaki Kando, Laser Accelerator Development at KPSI-QST .......................................................................................... 6
MOL1, H T Kim, Delopment of laser-plasma accelerator with multi-PW laser pulses....................................................... 7
MOL2, S Karsch, Overview of recent electron acceleration and X-ray generation results from Garching .............. 8
MOL3, Fei Li, Generating and Measuring High Quality Electron Beams in Plasma-based Accelerators .................. 9
MOL4, J L Shaw, The role of direct laser acceleration of electrons in a laser wakefield accelerator with
ionization injection ............................................................................................................................................................................................ 10
MOL5, A Irman, Single-shot measurement of electron bunch duration in laser wakefield acceleration .............. 11
MOL6, A Debus, Traveling-Wave Electron Acceleration: Breaking the dephasing and depletion limits of laser-
wakefield acceleration ..................................................................................................................................................................................... 12
MOL7, M krus, Short electron bunches accelerated by laser wakefield at PALS for applications from electron
diffraction to nuclear physics ...................................................................................................................................................................... 14
MOL8, D Gustas, Relativistic electron beams driven by single-cycle laser pulses at kilohertz repetition rate .. 15
MOR1, M Cernaianu, Back-reflection protection in high-power laser experiments using single plasma mirror
.................................................................................................................................................................................................................................... 16
MOR2, M Yeung, Relativistic plasma control using two-colour fields .................................................................................... 17
MOR3, C-K Huang, Electron Thermal Distribution Measurement of Above-Threshold Ionized He Plasmas ...... 18
MOR4, S Jinno, Development of Micron-size Hydrogen Cluster Targets for Laser-Plasma Interactions .............. 19
MOR5, Karl Zeil, Laser ion acceleration using the Draco Petawatt facility at HZDR - experiments and radio-
biological application....................................................................................................................................................................................... 20
MOR6, Liangliang Ji, Towards manipulating relativistic laser-plasma interaction with micro-structured targets
.................................................................................................................................................................................................................................... 21
2
MOR7, Wenpeng Wang, Experimental and simulation studies on muti-stage proton acceleration ....................... 22
MOR8, M Rehwald, Laser-proton acceleration from a condensed hydrogen jet .............................................................. 23
2. Tuesday, August 29
TUI1, Joshua Moody, First Self Modulation Instability Results from AWAKE: A Proton Driven Plasma
Accelerator ............................................................................................................................................................................................................ 24
TUI2, Sébastien Corde, Overview of the latest experimental advances in electron and positron beam-driven
plasma accelerators .......................................................................................................................................................................................... 25
TUL1, Hao Ding, Ultra-fast probing of plasma wave dynamics in a wakefield accelerator ......................................... 26
TUL2, Bu Guo, High resolution phase contrast images of biological specimens obtained from a 20TW laser 27
TUL3, V.B. Pathak, 10GeV electron bunch in dual-stage all-optical laser wakefield acceleration ............................. 28
TUL4, Amina E. Hussein, Stimulated Raman Backscatter from a laser wakefield accelerator ..................................... 29
TUL5, Aakash Sahai, Effect of plasma-wave topology on enabling high precision HEP using a plasma-based
collider..................................................................................................................................................................................................................... 30
TUL6, Michael Bussmann, Towards Exascale Simulations of Laser Plasma Interaction .................................................. 31
TUL7, Min Sup Hur, Burst of Ultraintense, Coherent Radiation from Colliding Laser Pulses in a Plasma ............ 32
TUL8, F Massimo, Numerical studies of density transition injection in laser wakefield acceleration ...................... 33
TUL9, K Lotov, Plasma wakefield excitation by a bunched proton beam ............................................................................. 34
TUL10, V Bychenkov, Laser acceleration of charged particles from low-density targets .............................................. 35
TUL11, D Wu, Particle-in-cell simulations of laser-plasma interactions at solid densities and relativistic
intensities: the role of atomic processes ............................................................................................................................................... 37
TUL12, Y Wan, Physical Mechanism of the Intrinsic Transverse Instability in Laser Pressure Ion Acceleration . 38
TUR1, M Coughlan, Ultrafast ion-induced dynamics in borosilicate glass ........................................................................... 39
TUR2, B Dromey, Electron solvation dynamics in H2O during ultrafast pulsed ion radiolysis .................................... 40
TUR3, C Brenner, Development of laser-solid plasma accelerators for industrial imaging and nuclear
inspection applications ................................................................................................................................................................................... 41
TUR4, W Bang, Rapid and uniform heating of matter with a laser-driven quasimonoenergetic aluminum ion
beam ........................................................................................................................................................................................................................ 42
TUR5, D Margarone, Proton acceleration from the interaction of a PW-class laser and a solid hydrogen
ribbon ...................................................................................................................................................................................................................... 44
TUR6, J Xu, Laser-Driven MeV Argon Ion Beam Generation with Narrow Energy Spread ........................................... 45
3
TUR7, C Lin, Recent Progress of Laser Ion Acceleration at Peking University .................................................................... 46
TUR8, PK Singh, Interaction of a Petawatt femtosecond laser with near-critical-density plasma ............................ 47
TUR9, J Hah, DD fusion neutron generation from low energy, fs-laser interaction with free flowing D2O ........ 49
TUR10, K Krushelnick, Enhancing betatron radiation in laser wakefield accelerators ..................................................... 50
TUR11, N Lemos, High-energy X/Gamma ray source from Compton scattering and Bremsstrahlung in a self-
modulated Laser Wakefield Accelerator ................................................................................................................................................ 51
TUR12, E gerstmayr, Experimental observation of strong radiation reaction effects in the interaction of a
high-intensity laser with a wakefield-accelerated electron beam ............................................................................................. 53
3. Wednesday, August 30
WEI1, Liming Chen, Enhancement of betatron X/γ-rays in a laser plasma accelerator ................................................. 54
WEI2, Arkady Gonoskov, Trapping electrons in a standing wave for ion acceleration and radiation generation
.................................................................................................................................................................................................................................... 55
WEI3, Wei Lu, Recent progress of laser plasma physics and advanced accelerator research at Tsinghua
University ............................................................................................................................................................................................................... 56
WEI4, Xinlu Xu, Recent progress in simulation and theory towards using nonlinear plasma wakefields to drive
a compact X-FEL ................................................................................................................................................................................................ 57
WEI5, A. G. R. Thomas, Laser Wakefield Accelerator Based Photon Sources ...................................................................... 58
4. Thursday, August 31
THI1, Samuel Barber, Emittance measurements and transport for the BELLA center free electron laser............. 59
THI2, Baifei Shen, Laser driven proton acceleration with solid and gas targets ............................................................... 60
THI3, Andreas Doepp, Stable, polarized betatron radiation and applications .................................................................... 61
THI4, Satyabrata Kar, Towards all-optical ion accelerator by an innovative target scheme ........................................ 62
THL1, M Marklund, Controlling radiation losses by quantum quenching .............................................................................. 63
THL2, T Blackbum, Scaling laws for positron production in laser—electron-beam collisions .................................... 65
THL3, Z Gong, Radiation reaction damping and ultra-intense gamma-ray flash generation in QED regime 66
THL4, M Vranic, Quantum vs. classical radiation reaction ............................................................................................................ 67
THR1, W Annenkov, New Generating Schemes of Tunable Narrowband Terahertz Radiation in Plasmas by
Femtosecond Laser Pulses ............................................................................................................................................................................ 68
4
THR2, M Mirzaei, Impact of injection-gas concentration of the quality of electron beam generated by laser
plasma acceleration .......................................................................................................................................................................................... 69
THR3, C Zhang, Femtosecond probing of plasma wakefields and observation of a plasma wake echo using a
relativistic electron bunch ............................................................................................................................................................................. 70
THR4, C Armstrong, High-energy bremsstrahlung radiation from laser-plasma accelerators from solid high-Z
targets to explore internal hot electron beam dynamics. ............................................................................................................. 71
1
Manipulating Relativistic Electrons with
Intense Laser Pulses
Victor Malka1,2*
1Laboratoire d’Optique Appliquée, CNRS, Ecole Polytechnique, ENSTA Paristech, Université Paris-Saclay, Palaiseau, France
2Weizmann Institute of Science, Rehovot, Israel *[email protected]
Laser Plasma Accelerators (LPA) rely on the control of the electronic motion with intense laser pulses [1].
The manipulation of electrons with intense laser pulses allows a fine mapping of the longitudinal and radial
components of giant electric fields that can be therefore optimized for accelerating charged particle or for
producing X rays. To illustrate the beauty of laser plasma accelerators I will show, how by changing the density
profile of the gas target, one can improve the quality of the electron beam, its stability [2] and its energy gain [3],
or by playing with the radial field one can reduce its divergence [4]. I’ll then show how by controlling the quiver
motion of relativistic electrons intense and bright X-rays beam are produced in a compact and elegant way [5-7].
Finally I’ll show some examples of applications.
References [1] V. Malka, Phys. of Plasmas 19, 055501 (2012) [2] E. Guillaume et al., Phys. Rev. Lett. 115, 155002 (2015). [3] C. Thaury Scientific Report, 10.1038, srep16310, Nov. 9 (2015) [4] C. Thaury et al., Nature Comm. 6, 6860 (2015) [5] K. Ta Phuoc et al., Nature Photonics 6, 308-311 (2012) [6] S. Corde et al., Review of Modern Phys. 85 (2013) [7] I. Andriyash et al., Nature Comm. 5, 4736 (2014)
2
Development and applications of betatron x-ray
radiation for high energy density science
Félicie Albert*
Lawrence Livermore National Laboratory, Livermore, CA 94550 USA *[email protected]
Betatron x-ray radiation, driven by electrons from laser-wakefield acceleration, has unique properties to probe
high energy density (HED) plasmas and warm dense matter. This source is produced when relativistic electrons
oscillate in the plasma wake of a laser pulse. Its properties are similar to that of a synchrotron, with a 1000-fold
shorter pulse. This presentation will focus on the experimental challenges and results related to the development
of betatron radiation for applications at large scale HED science laser facilities. We will present recent
experiments performed at the Linac Coherent Light Source (LCLS) at SLAC and the Jupiter Laser Facility (JLF)
at the Lawrence Livermore National Laboratory.
At LCLS, we have recently commissioned the betatron x-ray source, driven by the Matter under Extreme
Conditions (MEC) short pulse laser (1 J, 40 fs). The source is used as a probe by investigating the X-ray absorption
near edge structure (XANES) spectrum at the K- or L-edge of several materials (iron, silicon oxide) driven to a
warm dense matter state (temperature of a few eV, solid densities). The driver is either LCLS itself or optical
lasers. With these experiments we are able to study, with sub-picosecond resolution, the electron-ion equilibration
mechanisms in warm dense matter.
At JLF, we used the Titan laser (150 J, 1 ps), showing evidence of betatron x-ray production in the self-
modulated regime of laser-wakefield acceleration (SMLWFA). We will show a detailed source characterization,
as well as electron spectra above 200 MeV and forward laser spectra indicating a strongly self-modulated laser-
wakefield acceleration regime. The results, benchmarked against Particle-In-Cell (PIC) simulations, are promising
for future applications of the source at larger scale laser facilities such as OMEGA and NIF.
Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National
Laboratory under contract DE-AC52-07NA27344, supported by the LLNL LDRD program under tracking code
13-LW-076, 16-ERD-024, 16-ERD-041, supported by the DOE Office of Fusion Energy Sciences under SCW
1476 and SCW 1569, and by the DOE Office of Science Early Career Research Program under SCW 1575.
3
Electron and ion acceleration news from the novel
Petawatt laser facility in Dresden
U. Schramm*
Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany, and Technical University Dresden, Germany *[email protected]
Applications of laser plasma accelerated particle beams ranging from the driving of light sources to radiation
therapy require controlled scaling of particle beam energy and charge as well as reproducible operating conditions.
Both issues have motivated the development of novel table-top class Petawatt laser systems (e.g., 30J pulse energy
in 30fs) with unprecedented pulse control, here represented by the dual beam Draco-PW system recently
commissioned at HZDR Dresden.
First results will be presented on laser wakefield electron acceleration where in the beam loading regime high
bunch charges in the nC range could be efficiently accelerated with good beam quality, and on PW class proton
acceleration scaling. Several methods relying on target tailoring will be summarized to reliably provide about 10
MeV cut-off energy per Joule of laser energy up to the range of 25 MeV ready for applications. Here, pulsed
magnet beam transport ensures depth dose distributions allowing for tumor irradiation in dedicated animal models.
4
Staging Laser Wakefield Acceleration Research ai
ming for Repeatable GeV-class Accelerator
Tomonao HOSOKAI1, 2*, Takamitsu OTSUKA2, Naveen Pathak2, Junpei OGINO2, Yasuo SAKAI2, Alexei ZHIDKOV2, Keiichi SUEDA2, Shin’ichi MASUDA2, Hirotaka NAKAMURA1,
Zhang JIN 2, Akihiro UENO1, Hakujun TORAN1, and Ryosuke KODAMA1, 2, 3
1Graduate School of Engineering, Osaka University, Japan 2Photon Pioneers Center, Osaka University, Japan
3Institute of Laser Engineering, Osaka University, Japan *E-mail:[email protected]
A staging laser wakefield acceleration (LWFA) research that aims at table-top sized free-electron laser (FEL)
under the ImPACT program in Japan will be reviewed. LWFA is expected to be a novel scheme for accelerating
electron beams beyond GeV-class energy with compact devices. In recent studies, the pointing stability of the
electron beams from LWFA has been dramatically improved by plasma-micro-optics (PMO) that is plasma device
functioning as a focusing and optical-guiding tool for intense laser pulses [1]. The PMO enables electron beams
to be precisely controlled and/or transported by the beam-optics of conventional accelerators. With these
techniques a staging LWFA has been demonstrated successfully, and high quality quasi-mono-energetic beams
below the 100 MeV range are produced with good repeatability as an injector. Sub-GeV electron beams are also
produced with a 4 mm-booster laser wakefield. These results will be presented and discussed. A future
experimental site at SPring-8/RIKEN (Fig.1) is being prepared for the exclusive use of the laser-driven FEL. The
plans towards a test area on the laser-driven FEL at SPRING-8 /RIKEN will be presented.
Figure 1. A bird’s-eye view of laser system for LWFA platform at Spring-8/RIKEN site.
References
[1] T. Hosokai, et.al., Phys. Rev. Lett. 97, 075004 (2006); N. Nakanii, et.al., Phys. ReV. ST Accel. Beams. 18, 021303 (2015); T. Hosokai, et.al., Appl. Phys. Lett. 96, 121501 (2010); Y. Mizuta, et.al., Phys. ReV. ST Accel. Beams. 15, 121301 (2012); N. Nakanii, et.al., EPL, 113, 34002 (2016)
5
Development of 20-fs 4-PW laser for laser-plasma
accelerators Seong Ku Lee1,2*, Jae Hee Sung1,2, Hwang Woon Lee1, Jin Woo Yoon1,2, Je Yoon Yoo1 and
Chang Hee Nam1,3
1Center for Relativistic Laser Science, Institute for Basic Science, Gwangju, Korea 2Ultraintense Laser Laboratory, Advanced Photonics Research Institute, GIST, Gwangju, Korea
3Department of Physics and Photon Science, GIST, Gwangju, Korea *[email protected]
Ultra-high intensity lasers enable to investigate the novel physical phenomena such as laser driven particle
acceleration and strong field science. We have operated two ultra-intense petawatt (PW) beamlines [1, 2] and we
have recently upgraded a 20 fs, 4.2 PW laser [3]. In this talk, the development of a 20 fs, 4.2 PW Ti:sapphire laser
is presented.
Figure 1. Measured output energy as a function of pump energy in the final booster amplifier (left) and
reconstructed temporal profile of the 4.2 PW laser pulse (right).
For the 4.2 PW upgrade, the existing 1.5 PW beamline has been significantly modified. We, firstly, reduced
the pulse duration of the laser and then boosted the output energy. For the reduction of the pulse duration, the
spectral width was broadened by adopting the XPW and the OPCPA techniques and the final spectral width was
maximized by limiting the gain depletion of the next amplifiers. The output energy was boosted by adding a high
energy booster amplifier. With all the modification, we achieved the final compressed laser energy of 83 J and
the pulse duration of 19.4 fs, producing the 4.2-PW laser pulses at the repetition rate of 0.1 Hz with the low energy
fluctuation of 1.5% rms. This 4.2 PW laser is being operated and it will be a great tool for exploring the novel
physical phenomena in the unprecedented regime.
References [1] J. H. Sung et al, Opt. Lett. 35, 3021 (2010) [2] T. J. Yu et al., Opt. Express 20, 10807 (2012) [3] J. H. Sung et al., Opt. Lett. 42, 2058 (2017)
6
Laser Accelerator Development at KPSI-QST
Masaki Kando*
Kansai Photon Science Institute, National Institutes for Quantum and Radiological Science and Technology (QST) 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215, Japan
In Kansai Photon Science Institute (KPSI), National Institutes for Quantum and Radiological Science and
Technology (QST), we are developing laser-driven particle beams [1] for novel, compact sources including
protons, heavy ions, and electrons as well as photon sources ranging from 100’s eV to several MeV.
The ion acceleration study is based on target normal sheath acceleration (TNSA) by irradiating several
hundreds TW laser pulses onto foil targets. By carefully adjusting contrast level of our laser system J-KAREN-P
[2], the maximum proton energy reaches to ~ 50 MeV now (Mar. 2017) with a 2-µm-thick Al target. We also
improved the focal spot quality and the current strehl ratio measured on target is ~ 0.5 achieving~8.4x1021 W/cm2
[3].
The electron acceleration study is conducted using J-KAREN-P laser and a smaller system JLITE-X [4] at
KPSI-QST. We are developing plasma and electron real time monitors and testing an electron acceleration with
our J-KAREN-P laser. As for plasma monitors, we have developed sub-10-fs shadowgraph for direct plasma
density modulation [5] and holography for interferometric measurement [6]. In addition, we have demonstrated
characterization of pulse duration and timing of electron beams using electro-optic (EO) techniques [7].
References [1] T. Tajima and J.M.Dawson, Phys. Rev. Lett. 43, 267 (1979). [2] H. Kiriayam et al., IEEE J.S.T.Quantum Electron. 21, 1601118 (2015). [3] A. S. Pirozhkov et al., Opt. Express, submitted. [4] M. Mori et al., Laser Phys. 16, 1092 (2006). [5] A. Buck et al., Nat. Phys. 7, 543 (2011); A. Savert et al., Phys. Rev. Lett. 115, 055002 (2015). [6] N. H. Matlis et al., Nat. Phys. 2, 749 (2006). [7] X. Yan et al., Phys. Rev. Lett. 85, 3404 (2000); A. L. Cavalieri et al., Phys. Rev. Lett. 94, 114801 (2005).
7
Development of laser-plasma accelerator
with multi-PW laser pulses
H. T. Kim1,2*, J. H. Shin1, C. Aniculaesei1, B. S. Rao1, V. B. Pathak,1 M. H. Cho,1 S. K. Lee,1,2 J. H. Sung,1,2 H. W. Lee,1 J. Y. Yoo,1 J. W. Yun1,2, C. Hojbota,1,3 B. J. You1, S. H. Cho1, J. H. Jeon1,
K. Nakajima, and C. H. Nam1,3
1Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 61005, Republic of Korea 2Advanced Photonics Research Institute, GIST, Gwangju 61005, Republic of Korea
3Department of Physics and Photon Science, GIST, Gwangju 61005, Republic of Korea *[email protected]
The laser wakefield acceleration (LWFA) is one of the most attractive methods for next generation electron
accelerators because it provides huge acceleration field larger by three orders of magnitude than that of
conventional rf accelerators. The development of PW lasers has prompted the investigation of a new regime in
laser electron acceleration. We have developed two PW Ti:Sapphire laser beamlines [1], and successfully applied
the PW laser pulses to generate a 3-GeV electron beam [2]. Recently, we demonstrated a new method to stabilize
multi-GeV electron beams by controlling the waveform of PW laser pulses [3]. At CoReLS, we have upgraded
one of the PW laser beamlines to a 20-fs, 4-PW laser [4], which can offer opportunities to achieve a 10-GeV
electron beam and to explore QED effects in nonlinear Compton backscattering process. We present the current
status and future plans on developing electron accelerator using the 4-PW laser.
References [1] J. H. Sung, S. K. Lee, T. J. Yu, T. M. Jeong, and J. Lee, Opt. Lett. 35, 3021 (2010). [2] H. T. Kim et al., Phys. Rev. Lett. 111, 165002 (2013). [3] H. T. Kim et al., Sci. Rep. (Accepted). [4] J. H. Sung et al., Opt. Lett. 42 (11), 2058 (2017).
8
Overview of recent electron acceleration and X-ray
generation results from Garching
Stefan Karsch1,2*, Max Gilljohann1, Johannes Götzfried1, Hao Ding1, Sabine Schindler1, Johannes Wenz1, Konstantin Khrennikov1, Matthias Heigoldt1, Mathias Hüther1, Ludwig Wildgruber1, Lorenz Hehn3,
Franz Pfeiffer3, Gavin Cheung4, Simon Hooker4, Andreas Döpp
1Ludwig- Maximilians-Universität München (LMU), Am Coulombwall 1, 85748 Garching, Germany 2MPI für Quantenoptik (MPQ), Hans-Kopfermann-Strasse 1, 85748 Garching, Germany
3Technische Universität München (TUM), James-Franck-Strasse 1, 85748 Garching, Germany 4University of Oxford, Parks Road, Oxford OX1 3PU, UK
After its move from MPQ to an interim location at the LEX facility at the LMU, the ATLAS laser has recently
been upgraded to 200 TW peak power, serving a new experimental area with electron acceleration and ion
acceleration beamlines. We will report on the first campaign with the new system in 2016. Electron acceleration
has been studied in various injection schemes, yielding high-charge beams (up to nC level) with broadly tunable
parameters (0.1-1.5 GeV). The combination of shock-front and colliding pulse injection yields two independently
tunable, quasi-monochromatic electron bunches with prospect for driver-witness-type PWFA experiments. A few-
cycle shadowgraphy/faraday rotation probe pulse was used for the study of wakefields and beam currents down
to the low 1018 cm-3 density regime. In addition to the first observation of a fully broken bubble in the LWFA
process, this diagnostic also proved the excitation of a wake by the primary LWFA electron bunch in a secondary
plasma target as a first step towards true hybrid acceleration schemes.
In the field of X-ray generation, we continued our successful previous work [1] towards applications of
betatron radiation in medical imaging. Furthermore, we performed measurements and imaging using both single-
pulse [2] and dual-pulse [3] Thomson scattering.
Finally, we will give a brief status update of the ongoing 3-PW upgrade of ATLAS in the new CALA
laboratory.
References [1] J. Wenz et al. Quantitative X-ray phase-contrast microtomography from a compact laser-driven betatron source. Nat.Comms. (2015) [2] Ta Phuoc et al. All-optical Compton gamma-ray source. Nat.Phot. (2012) [3] K. Khrennikov et al., Tunable All-Optical Quasimonochromatic Thomson X-Ray Source in the Nonlinear Regime, PRL 114 195003 (2015)
9
Generating and Measuring High Quality Electron
Beams in Plasma-based Accelerators
Fei Li1, Xinlu Xu2*, Chaojie Zhang2, Yang Wan1, Yipeng Wu1, Jianfei Hua1, Chih-Hao Pai1, Wei Lu1,*, Warren B. Mori2 and Chan Joshi2
1Department of Engineering Physics, Tsinghua University, Beijing 100084, China
2University of California, Los Angeles, Los Angeles 90095, United States *[email protected]
The plasma-based accelerators (PBA) have experienced tremendous progress in the last decade, which is
promising to revolutionize the applications of laser and accelerator technologies. One of the key challenges for
PBA is how to controllably generate the high quality electron beams largely exceeding those the state-of-art
accelerator techniques can achieve. By understanding the general rules of the injection in PBA, two novel schemes
based on the ionization injection and the plasma density modulation injection are proposed and deeply studied.
PIC simulations show the schemes can generate high quality electron beams with low slice energy spread (~10
keV to ~1 MeV), ultralow emittance (nm to tens of nm level), high current (~kA to ~20 kA level) and ultrahigh
brightness (1019 to 1022 A m-2 rad-2) which is 3 to 6 orders of magnitude higher than the current techniques. Once
verified experimentally, it will produce important influence on the development of the future light source and the
linear collider technologies. In order to precisely and efficiently simulate the beam dynamics during the injection,
a novel PIC algorithm with high parallelization and low noise is proposed and implemented.
The issue of measuring ultralow emittance is deeply discussed. Focusing on the high-gradient permanent
magnetic quadrupole (HGPMQ) method, the error and reliability analyses are systematically carried out,
confirming its potential for measuring ultralow emittance (<0.1 mm mrad). Experimental system with 50 nm
emittance resolution is designed and manufactured, and the measurement of mm mrad level emittance is
preliminarily realized, which lays the foundation for the future experiments.
10
The role of direct laser acceleration of electrons in
a laser wakefield accelerator with ionization
injection
J.L. Shaw 1,2*, N. Lemos 1, L.D. Amorim 1, N. Vafaei-Najafabadi 1, K.A. Marsh 1, F.S. Tsung 1, W.B. Mori 1, D. H. Froula 2, and C. Joshi 1
1University of California Los Angeles, Los Angeles CA USA
2Laboratory for Laser Energetics, Rochester NY USA *[email protected]
We show through experiments and supporting simulations the role of direct laser acceleration (DLA) of
electrons in a laser wakefield accelerator when ionization injection of electrons is employed. The laser pulse is
intense enough to create a nonlinear wakefield and long enough to overlap the electrons trapped in the first
accelerating potential well (bucket) of the wakefield. The betatron oscillations of the trapped electrons in the plane
of the laser polarization in the presence of an ion column lead to an energy transfer from the laser pulse to the
electrons through DLA. We show that the produced electron beams exhibit characteristic features that are
indicative of DLA as an additional acceleration mechanism when the laser pulse overlaps the trapped electrons.
This material is based upon work supported by the Department of Energy National Nuclear Security
Administration under Award Number DE-NA0001944, the University of Rochester, and the New York State
Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE
of the views expressed in this article.
11
Single-shot measurement of electron bunch
duration in laser wakefield acceleration
Arie Irman1*, O. Zarini1,2, J.P. Couperus1,2, R. Pausch1,2, A. Köhler1,2, J.M. Krämer1,2, T. Kurz1,2, A. Debus1, M. Bussmann1, U. Schramm1,2
1Institute of Radiation Physics, Helmholtz-Zentrum Dresden – Rossendorf, 01328 Dresden, Germany
2Technische Universität Dresden, 01069 Dresden, Germany *[email protected]
Laser-wakefield accelerators (LWFA) feature electron bunches with duration ranging from several fs to tens
of fs. Precise knowledge of the longitudinal profile of such ultrashort electron bunches is essential for the design
of the next generation of light-sources and still remains a big challenge due to the resolution limit of existing
diagnostic techniques. Here we present measurement of electron bunch duration by recoding incoherent and
coherent transition radiation emitted as LWFA electron bunches passing through a metal foil. For this purpose, a
broadband spectrometer covering the spectral range from UV to MID-IR at very high dynamic range was deployed
in a single shot mode. We discuss the longitudinal structure of LWFA bunches from different injection mechanism
and possible path for generation of high peak current electron beam with a good beam quality.
12
Traveling-Wave Electron Acceleration:
Breaking the dephasing and depletion limits of
laser-wakefield acceleration
Alexander Debus1,*, Richard Pausch1,2, Axel Huebl1,2, Klaus Steiniger1,2, René Widera1, Tom Cowan1,2, Ulrich Schramm1,2, and Michael Bussmann1
1 Helmholtz-Zentrum Dresden – Rossendorf (HZDR),Bautzner Landstrasse 400, 01328 Dresden, Germany
2 Technische Universität Dresden, 01062 Dresden, Germany *[email protected]
We show how to simultaneously solve several longstanding limitations of laser-wakefield acceleration that
have thus far prevented laser-plasma electron accelerators (LWFA) to extend into the energy realm beyond 10
GeV. Most prominently, our novel Traveling-Wave Electron Acceleration (TWEAC) approach [1] eliminates
both the dephasing and depletion constraints, which fundamentally limit the maximum energy gain of a single
LWFA stage. This is complemented with a focusing geometry, which does not require any guiding structures,
such as plasma-capillaries, and does not rely on laser self-guiding in plasma. This opens up acceleration regimes
that were previously inaccessible.
The wakefield driver is a region of overlap of two obliquely incident, ultrashort laser pulses with tilted
pulse-fronts in the line foci of two cylindrical mirrors, aligned to coincide with the trajectory of subsequently
accelerated electrons. First, such a laser geometry drives a wakefield moving at the vacuum speed of light
instead of the sub-luminal group-velocity vg<c, thus preventing electrons from outrunning the plasma wave
(dephasing limit). Secondly, this leads to a stable and experimentally controllable plasma cavity by having at
every instant a new, unspoilt section of the laser pulse, which has not yet undergone self-phase modulation,
transversely entering the plasma and, after only a short propagation distance, form the acceleration cavity in
plasma regions previously unperturbed by lasers. That latter mechanism eliminates the pump depletion limit of
LWFA.
TWEAC presents a prospect of vastly reducing or even completely disposing the problem of staging
between several LWFAs to achieve higher energies and hence averts the loss of electron beam quality, such as
charge decrease due to inter-stage beam transport or laser-stage-coupling inefficiencies. Given enough laser
pulse energy and in contrast to LWFA and PWFA, TWEAC can arbitrarily be extended in length to higher
electron energies without changing the underlying acceleration mechanism.
We show that TWEAC leads to quasi-static acceleration conditions, which do not suffer from laser self-
phase modulation, parasitic self-injection or other plasma instabilities. Similarly, the TWEAC geometry greatly
facilitates reducing beam transport distances between the laser-plasma accelerator and subsequent insertion
devices, such as undulators, plasma lenses or colliding laser pulses, to below millimeters. This is especially
critical for reducing emittance growth during beam transport.
13
We introduce the new acceleration scheme, show results from 3D particle-in-cell simulations using
PIConGPU, discuss energy scalability for both laser and electrons and elaborate on experimental realization
requirements.
References [1] Debus et al., “Breaking the dephasing and depletion limits of laser-wakefield acceleration”, paper submitted.
14
Short electron bunches accelerated by laser
wakefield at PALS for applications from electron
diffraction to nuclear physics
Miroslav Krus*
Institute of Plasma Physics of the Czech Academy of Sciences, Department of Laser Plasma, Czech Republic *[email protected]
Advances in the laser technology drive the development of charged particles´ plasma-based laser
accelerators, being compact devices capable of electron bunch acceleration to several hundreds of MeV over
milimeter distances. However, present-day laser accelerated electron beams lack the parameters and stability of
modern, conventional RF accelerators.
Here, we present the recent experimental (using 400mJ-in-focus, 40fs, 808nm laser pulses available at PALS
Research Infrastructure) and numerical results on the stabilization of the in-plasma-wave electron beam injection
process by shock-wave-driven plasma-density downramp tailoring or perpendicularly crossed optically-driven
electron bunch injection. Using these techniques, fundamental electron beam parameters can be fitted for
production of high-quality beams used in various applications (e.g. electron diffraction, radiography, X-ray and
radioisotope production, etc.).
15
Relativistic electron beams driven by single-cycle
laser pulses at kilohertz repetition rate
D. Gustas, D. Guénot, A. Vernier, F. Böhle, R. Lopez-Martens, A. Lifschitz, J. Faure*
LOA, ENSTA Paristech, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91120 Palaiseau, France *[email protected]
We will review our recent developments on a high repetition rate MeV electron source and its potential
applications. Due to significantly reduced space charge and velocity dispersion effects, relativistic electron
bunches accelerated by laser wakefields have been identified as a candidate tool to achieve unprecedented sub-
10 fs temporal resolution in ultrafast electron diffraction (UED) experiments [1], [2]. High repetition rate
operation is also desirable to improve data collection statistics and wash out shot-to-shot charge fluctuations
inherent to plasma accelerators. It is well known that high-quality electron beams with narrow energy spreads and
small divergences can be achieved in the blowout, or bubble wakefield regime [3], which is at present regularly
accessed with ~30 fs Joule-class lasers that can perform up to few shots per second. Our group on the contrary
employed a cutting edge laser system producing few-mJ pulses compressed nearly to a single optical cycle (3.4
fs) [4] to demonstrate for the first time that, consistently with the scaling laws [5], relativistic electron beams with
properties characteristic to the blowout regime and peaked at 4-6 MeV energy can also be achieved at kilohertz
repetition rate [6]. We further investigate the plasma density profile effects on the accelerated charge and electron
energy and show that using certain structured gas jets several tens of pC/shot can be achieved. We expect this
technique to lead to a highly accessible and robust instrument for the scientific community to conduct UED
experiments with sub-10 fs temporal resolution.
Figure 2. Typical electron beam profile and spectrum [6]
References [1] J. Faure et al., Phys. Rev. Accel. Beams 19, 021302 (2016) [2] Z.-H. He et al., Sci. Rep. 6, 36224 (2016) [3] A. Pukhov and J. Meyer-ter-Vehn, Appl. Phys. B 74, 355-361 (2002) [4] F. Böhle et al., Laser Phys. Lett. 11, 095401 (2014) [5] W. Lu et al., Phys. Rev. Accel. Beams 10, 061301 (2007) [6] D. Guénot et al., Nat. Photon. 11, 293-296 (2017)
16
Back-reflection protection in high-power laser
experiments using single plasma mirror
M.O. Cernaianu1*, P. Ghenuche1, D. Ursescu1, Y. Hayashi2, H. Habara2, B. Diaconescu1, D. Stutman1 and K. A. Tanaka1
1Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) – Extreme Light Infrastructure –
Nuclear Physics (ELI-NP), Bucharest-Magurele, Romania 2Graduate School of Engineering, Osaka University, Osaka, Japan
In high-intensity laser interactions with solid targets, the radiation pressure can push inwards the plasma
produced by the intense laser light and form a density hole with transverse dimensions comparable to the incident
light [1], or can modulate the target surface [2, 3]. Recent measurements with PW class lasers demonstrated that
energies of up to 3% of the incident laser energy can be back-reflected in the laser system [2]. Given the foreseen
intensities in the ELI-NP experiments in the range of 1022-1023 W/cm2, back-reflections of the main laser pulse
can occur from the distorted plasma, leading to damages of the beam transport system optics or even to the laser
amplification chain. Due to the large beam diameters of the ELI-NP high-power laser, conventional optical
insulators cannot be used [4]. We are therefore investigating the solution of using a single plasma mirror as a
back-reflection suppressor. Using the simulated and measured laser temporal contrast profile of the ELI-NP laser,
we are presenting the first simulation results in the evaluation of the target behavior and its optimum
characteristics necessary to mitigate a back-reflected pulse. A design for the implementation of the plasma mirror
setup is also discussed.
Figure 3. Left: Hydrodynamic simulation of 3% back-reflected 10 PW laser pulse on a thin-film C plasma mirror target. Right: Conceptual setup for 10 PW sacrificial mirror solution.
References [1] W. B. Atwood, et al., Phys. Rev. Lett. 40, 184 (1978)
Sacrificial
mirrors Targets
10 PW
17
Relativistic plasma control using two-colour fields
Mark Yeung1*, Sergey Rykovanov2, Jana Bierbach2,3, Lu Li1, E. Eckner3, Stephan Kuschel2,3, Abel Woldegeorgis2,3, Christian Rödel2,3,4, Alexander Sävert3, Gerhard G. Paulus2,3, Mark Coughlan1, Brendan
Dromey1 and Matthew Zepf1,2,3
1Department of Physics and Astronomy, Queen’s University Belfast, Belfast,, UK
2Helmholtz Institute Jena, Fröbelstieg 3, Jena, Germany 3Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, Jena, Germany
4SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California, USA *[email protected]
The interaction of a sufficiently intense laser pulse with an initially solid target can result in the formation of
a plasma in which surface electrons are accelerated to relativistic speeds on time scales shorter than a laser cycle.
These electrons can form dense bunches and emit radiation that is upshifted in frequency relative to that of the
incident laser pulse, reaching up to extreme-ultraviolet (XUV) or even X-ray photon energies [1,2]. As this
process repeats periodically with the laser, this upshifted radiation is emitted in the form of high harmonics of the
laser frequency. Here, we show clear experimental data demonstrating that this process can be controlled by
converting part of the incident laser energy into its second harmonic before it is incident on the target surface.
Fine tuning of the sub-cycle timing of this second harmonic pulse can significantly alter the shape of the incident
waveform, which modifies the trajectories of the electrons, and can lead to a dramatic increase of the efficiency
at which energy is converted into XUV radiation [3]. As well as providing insights into the relativistic dynamics
of surface electrons in these interactions, this has the potential to lead to new laser based, coherent XUV sources
with unprecedented pulse energies and even attosecond scale pulse durations.
Figure 4. Experimentally observed high harmonic signal for different phases of the 2nd harmonic relative to the fundamental laser pulse. Tuning the phase controls the harmonic generation efficiency and the highest order
observed which is directly linked to the dynamics of the relativistic electrons in the target.
References [1] R. Lichters et al., Phys. Plasmas, 3, 3425 (1996) [2] B. Dromey et al., Nature Physics, 2, 456 (2006) [3] M. Yeung et al., Nature Photon. 11, 32 (2016)
18
Electron Thermal Distribution Measurement of
Above-Threshold Ionized He Plasmas
Chen-Kang Huang*, Chaojie Zhang, Ken Marsh, Chris Clayton, and Chan Joshi
Electrical Engineering Department, University of California, Los Angeles, USA *[email protected]
Above-threshold ionization (ATI) has been shown to be an effective way to heat a plasma [1]. The quasi-
classical theory of tunnel ionization implies that a plasma optically ionized by a circularly polarized pulse can
have electrons several times hotter than by a linearly polarized one. Electrons emitted from optically ionized
plasmas with high kinetic energy have been measured through experiments [2, 3]. However, the detailed dynamics
of ATI heating has not yet been shown experimentally. We propose an experiment to use Thomson scattering to
characterize the helium plasma after optical-field ionization by intense femtosecond pulses. The time evolution
of plasma electron distribution will be measured using an independently delayed femtosecond probe beam with 5
nm bandwidth. The anisotropic energy distribution from a linearly polarized laser pulse predicted by quasi-
classical theory will also be verified.
References [1] N. H. Burnett and P. B. Corkum, J. Opt. Soc. Am. B. 6, 1195 (1989). [2] P. B. Corkum, N. H. Burnett, and F. Brunel, Phys. Rev. Lett. 62, 1259 (1989). [3] M. H. Sher, H. W. K. Tom, G. D. Aumiller, O. R. Wood II, R. R. Freeman, and J. Bokor, Phys. Rev. Lett. 71, 509 (1993).
19
Development of Micron-size Hydrogen Cluster
Targets for Laser-Plasma Interactions
S. Jinno,1 M. Kanasaki,2 M. Uno,2 R. Matsui,3 M. Uesaka,1 Y. Kishimoto,3 and Y. Fukuda4
1Nuclear Professional School, The University of Tokyo, 2-22 Shirakata Shirane, Tokai, Naka, Ibaraki 319-1188, Japan 2Graduate School of Maritime Sciences, Kobe University, 5-1-1 Fukaeminamimachi, Higashinada, Kobe, Hyogo 658-0022,
Japan 3Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
4Kansai Photon Science Institute (KPSI), National Institutes for Quantum and Radiological Science and Technology (QST), 8-1-7 Umemidai, Kizugawa, Kyoto 619-0215, Japan
The recent advancements in laser-driven ion acceleration techniques using thin foil targets allow the maximum
proton energies close to 100 MeV [1,2]. From a view point of practical applications, high-purity proton beams
with high reproducibility are quite advantageous. In experiments using thin foil targets, however, protons from
surface contaminants along with the high-z component materials are accelerated together, making the production
of impurity-free proton beams unrealistic. Here we propose another way to produce impurity free, highly
reproducible, and robust proton beams exceeding 100 MeV using Coulomb explosion of micron-size hydrogen
clusters. For example, 100 MeV protons could be produced via the Coulomb explosion of the 1.2 m diameter
hydrogen cluster when irradiated by a laser pulse with a peak intensity of 1.6 × 1021 W/cm2.
In this study, the micron-size hydrogen clusters were generated by expanding the supercooled high-pressure
hydrogen gas into a vacuum via a conical nozzle connected to a solenoid valve cooled by a cryogenic refrigerator.
The size distribution of the hydrogen clusters is evaluated by measuring the angular distribution of laser light
scattered from the cluster [3,4]. The data were analyzed based on Mie scattering theory combined with Tikhonov
regularization method. The size distribution of the hydrogen clusters was found distributed from 0.3-2.0 m. The
background gas density profile of the targets is also evaluated using a Nomarski interferometer assuming the
cylindrical symmetry of the target.
The 3D Particles-in-Cell (PIC) simulations concerning interaction processes of micron-size hydrogen clusters
with high power laser pulses predict the generation of protons exceeding 100 MeV, accelerated in a laser
propagation direction via an anisotropic Coulomb explosion mechanism, demonstrating a future candidate in
laser-driven proton sources with the upcoming multi-PW lasers [5].
References [1] F. Wagner et al., Phys. Rev. Lett. 116, 205002 (2016). [2] I. J. Kim et al., Phys. Plasmas 23, 070701 (2016). [3] S. Jinno et al., Appl. Phys. Lett. 102, 164103 (2013). [4] S. Jinno, et al., Optics Express 21, 20656 (2013). [5] C. Danson et al., High Power Laser Science and Engineering 3, e3 (2015).
20
Laser ion acceleration using the Draco Petawatt
facility at HZDR - experiments and radio-biological
application
K. Zeil1*, L. Obst1,2, M. Rehwald1,2, F. Brack1,2, J. Metzkes1, S. Kraft1, H.-P. Schlenvoigt1, T. Ziegler11,2, A. Jahn1,2, F. Kroll1,2, T. Kluge1, T. Cowan1,2, U. Schramm1,2
1Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany
2Technical University Dresden, Germany *[email protected]
Demanding applications like radiation therapy of cancer are pushing the frontier of laser driven proton
accelerators with controlled and well-defined proton beam properties. This talk will give an overview of recent
achievements at the high-contrast high power laser source DRACO at the HZDR in Dresden (Germany). The laser
system was recently upgraded by an additional Petawatt (PW) amplifier stage and new front end components
finally providing high contrast pulses of >500 TW on target at 1 Hz pulse repetition rate. In first experiments the
delivery of these pulses on target was demonstrated and the feasibility of worldwide first controlled volumetric
irradiation of a specifically developed tumor model, grown on the ears of nude mice with laser-accelerated protons
was investigated. In order to efficiently capture and shape the divergent TNSA proton beam, a setup of two pulsed
high-field solenoid magnets will be presented to reliably generate homogeneous dose distributions in lateral
direction and in depth.
The performance of laser based proton and ion acceleration and the scaling of the laser energy to achieve
increased ion energies strongly depend on the laser temporal contrast and its effect on the target plasma scale
length. Plasma mirror setups have proven to be a valuable tool to significantly improve the temporal contrast by
reducing pre-pulse intensity and steepening the rising edge of the main laser pulse. Re-collimating single plasma
mirror devices have been implemented into the Draco laser beam lines and the talk will summarize on
measurements of the resulting contrast enhancement comparing different techniques. With the achieved contrast
enhancement, laser proton acceleration and proton energy scaling were investigated within the TNSA regime
using ultra-thin foil targets and implications for the radiobiological experiments will be discussed.
21
Towards manipulating relativistic laser-plasma
interaction with micro-structured targets
Liangliang Ji*
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciencies, Shanghai 201800, China *[email protected]
Efficient coupling of intense laser pulses to solid-density matter is critical to many applications including ion
acceleration for cancer therapy. At relativistic intensities, the focus has been mainly on investigating various laser
beams irradiating initially overdense flat interfaces with little or no control over the interaction. With recent
development on pulse cleaning technique, such as XPW and the use of plasma mirror, we now propose a novel
approach that leverages advancements in 3D nano-fabrication of materials and high contrast lasers to manipulate
the laser-matter interactions on the micro-scales. The advanced technique can produce repeatable structures with
at a resolution as high as 100 nm. Based on 3D PIC simulations, we explored two typical structures, the micro-
cylinder and micro-tube targets. The former serves to enhance and control laser-electron acceleration and the latter
is dedicated to manipulate relativistic light intensity. First principle-of-proof experiments were carried out in the
SCARLET laser facility located in the Ohio State University and confirmed some of our predictions on enhancing
direct laser acceleration of electrons. We believe that the use of the micro-structured elements provides another
degree of freedom in LPI and these results will open new paths towards micro-engineering interaction process
that will benefit high field science, laser-based proton therapy, near-QED physics, and relativistic nonlinear optics.
References [1] S. Jiang et al, Phys. Rev. Lett. 116, 085002 (2016) [2] L. L. Ji et al, Scientific Reports, 6, 23256 (2016) [3] J. Snyder et al, Phys. Plasmas 23, 123122 (2016)
22
Experimental and simulation studies on muti-stage
proton acceleration
Hyung Taek Kim* and Chang Hee Nam
W. P. Wang, B. F. Shen*, H. Zhang, X. M. Lu, J. F. Li, S. H. Zhai, S. S. Li, X. L. Wang, R. J. Xu, C. Wang, Y. X. Leng, X. Y. Liang, R. X. Li, and Z. Z. Xu**
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of
Sciences, Shanghai 201800, China * E-mail address: [email protected]
** E-mail address: [email protected]
With the development of ultra-intense laser technology, laser intensity can increase up to the order of ~1022
W/cm2 in the laboratory. Ion beams in the MeV range and even the GeV range, driven by terawatt or petawatt
lasers, exhibit ultra-short pulse duration, excellent emission, and ultra-high peak current. Thus, they can
potentially be applied in fast ignition of inertial confinement fusion, medical therapy, proton imaging, and pre-
accelerators for conventional acceleration devices. However, the generation of quasi-monoenergetic proton beams
for realistic applications is still an experimental challenge. Here, the optimum and controllable two-stage proton
acceleration is realized for the first time by a novel double beam image (DBI) technique in experiment. Two laser
pulses are successfully tuned on two separated foils with both spatial collineation and time synchronizing,
resulting in spectrum tailoring and an energy increase at the same time. Such a novel DBI technique can help us
to realize the optimum two-stage acceleration in a feasible way, which opens the door for the exact manipulation
of multi-stage acceleration to further improve the energy and spectra of particle beams.
Figure 5. (a) Proton images on RCFs for the two-stage proton acceleration. Laser one (L1) irradiates on target one(T1), and Laser one (L2) irradiates on target one(T2). (b) The relation between optimum optical path
difference（LOPD） and the proton energy Ep. Energetic spectra for (c) LOPD = 3.64 cm, (d) LOPD = 4.86 cm, and (e) LOPD = 6.3 cm. The images on IP plates for the cases of (f) L1 + T1, (g) L2 + T2, and (h) L1 + T1 and L2 +
T2.
23
Laser-proton acceleration from a condensed
hydrogen jet
M. Rehwald1*, K. Zeil1, L. Obst1, F. Brack1, J. Metzkes1, S. Kraft1, H.-P. Schlenvoigt1, P. Sommer1, T. Kluge1, T. Cowan1, U. Schramm1, S. Goede3, S. Wolter4, L. Kazak4, M. Gauthier2,
M. MacDonald2, W. Schumaker2, S. Glenzer2, R. Mishra2, C. Ruyer2, F. Fiuza2, C. Roedel2
1Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany 2SLAC National Accelerator Laboratory, Menlo Park, United States
3European XFEL GmbH, Schenefeld, Germany 4University Rostock, Germany
The presentation will give an overview of recent experiments for laser driven proton acceleration with high
contrast at the high power laser system Draco at HZDR. We present results of an experimental campaign
employing a pure condensed hydrogen jet as a renewable and debris free target.
Different ion diagnostics reveal mono-species proton acceleration in the laser incidence plane around the wire-
like target, reaching cut-off energies of up to 20 MeV and exceeding 109 protons per MeV per steradian.
Evaluations of two different target geometries (cylindrical with a diameter of 2µm, 5µm or 10µm and planar with
2x20 µm²) demonstrate more optimized acceleration conditions using the planar hydrogen jet.
We report on modulations of laser accelerated protons by strong filamentary electromagnetic fields. Those
modulations are related to the appearance of electron Weibel instability in the preplasma at the rear side of the
target and impose important constraints on the preplasma level for high-quality proton acceleration [1].
Furthermore we present the usage of optical probing to study the laser plasma interaction providing plasma
density measurements at the time of the interaction and to precisely determine the jet position. Recorded probe
images taken up to 100 ps after the laser pulse arrived at the target, indicate plasma density modulations from
pinching effects along the jet axis.
References [1] S. Göde et al., recently accepted by PRL
24
First Self Modulation Instability Results from
AWAKE: A Proton Driven Plasma Accelerator
Joshua Moody*
Max Planck Institute for Physics, Föhringer Ring 6, 80805 Munich, Germany *[email protected]
AWAKE is a proton driven plasma wakefield experiment at CERN [1]. A ten meter vapor source is used to
create rubidium with a precise and tunable baseline density of 7*10 14 cm-3, with an associated singly ionized
plasma skin depth (c/wp) of 1.2 mm. Because the 400 GeV proton beam from the super proton synchrotron (SPS)
is significantly longer than the plasma skin depth, AWAKE must rely on the transverse self-modulation instability
(SMI) to apply feedback on the proton beam, causing modulation at the plasma skin depth and thereby allowing
it to resonantly drive the wakefields to create GV/m fields. Furthermore, SMI must compete with other plasma
instabilities so it must be seeded by igniting the plasma within the proton beam with a 4.5 TW laser pulse. In this
presentation, I will discuss the first results of the measurements of SMI at AWAKE, the physics of SMI and that
of the ionization required to seed it, the nature of the plasma source, the diagnostics used to measure SMI, and the
planned future of AWAKE.
References [1] E. Gschwendtner, et al AWAKE, The Advanced Proton Driven Plasma Wakefield Acceleration Experiment at CERN, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol 829, 1 September 2016, Pages 76-82, ISSN 0168-9002, https://doi.org/10.1016/j.nima.2016.02.026.
25
Overview of the latest experimental advances in
electron and positron beam-driven plasma
accelerators S. Corde1*, A. Doche1, J. M. Allen2, C. I. Clarke2, J. Frederico2, S. J. Gessner2, S. Z. Green2, M. J Hogan2, M. D. Litos2, B. O’Shea2, V. Yakimenko2, W. An3, C. E. Clayton3, C. Joshi3, K. A. Marsh3, W. B. Mori3, N.
Vafaei-Najafabadi3, E. Adli4, C. A. Lindstrøm4 and W. Lu5
1LOA, ENSTA ParisTech, CNRS, Ecole Polytechnique, Université Paris-Saclay, 91762 Palaiseau, France 2SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
3University of California Los Angeles, Los Angeles, CA 90095, USA 4Department of Physics, University of Oslo, 0316 Oslo, Norway
5Department of Engineering Physics, Tsinghua University, Beijing 10084, China *[email protected]
Plasma accelerators driven by particle beams promise high electric fields and high efficiencies, and are
increasingly considered as a mean to make future electron-positron colliders more compact and affordable. Beam-
driven plasma acceleration of electrons and positrons has recently seen a rapid experimental progress, in particular
with experiments conducted at the FACET facility (Facility for Advanced Accelerator Experimental Tests) at
SLAC National Accelerator Laboratory.
I will present an overview of the key results for plasma acceleration of both electrons and positrons, obtained
by the E200 collaboration during the 2012-2016 FACET experimental runs. For electrons, the acceleration of a
distinct bunch was achieved with high energy efficiency [1], and the field structure of the highly nonlinear plasma
wake has been characterized [2]. Very high fields in a beam-ionized high-ionization-potential gas were also
generated, unveiling important physical processes such as particle beam self-focusing [3]. The more challenging
problematic of positron acceleration will also be reviewed. A new regime where energy is efficiently transferred
from the front to the rear within a single positron bunch was discovered. The self-loading of the wake leads to the
formation of a narrow energy spread bunch of positrons [4]. The acceleration of a distinct positron bunch in a
plasma wake was also demonstrated at the culmination of the five-year campaign, in an experiment spanning
nonlinear to quasi-linear regimes and unveiling beam loading effects. Finally, the use of hollow plasma channels
for positrons was also investigated [5], and positrons have been successfully accelerated in these tubes of plasma.
References [1] M. Litos et al., Nature 515, 92 (2014). [2] C. E. Clayton et al., Nat. Commun. 7, 12483 (2016). [3] S. Corde et al., Nat. Commun. 7, 11898 (2016). [3] S. Corde et al., Nat. Commun. 7, 11898 (2016). [4] S. Corde et al., Nature 524, 442 (2015). [5] S. Gessner et al., Nat. Commun. 7, 11785 (2016).
26
Ultra-fast probing of plasma wave dynamics in a
wakefield accelerator
Hao Ding1, Max Gilljohann1, Johannes Götzfried1, Sabine Schindler1, Felix Daiber1, Ludwig Wildgruber1, Johannes Wenz1, Konstantin Khrennikov1, Matthias Heigoldt1, Mathias Hüther1, Andreas Döpp1,
and Stefan Karsch1,2*
1Ludwig- Maximilians-Universität München (LMU), Am Coulombwall 1, 85748 Garching, Germany
2MPI für Quantenoptik (MPQ), Hans-Kopfermann-Strasse 1, 85748 Garching, Germany *[email protected]
We report on results obtained with a few-cycle microscopic diagnostic [1] at the ATLAS laser facility. This
diagnostic allows direct observation of the laser-plasma interaction at densities of a few 1018 cm-3. In particular,
we have investigated the evolution of plasma waves for different injection schemes and have used Faraday rotation
[2] as complementary diagnostic to measure the electron bunch length. Furthermore, we directly observe - for the
first time - that the laser-accelerated electron beam drives its own plasma wave in a second, subsequent gas jet
target, paving the way for hybrid-wakefield accelerator schemes [3].
References [1] A. Savert et al., Phys. Rev. Lett. 115, 055002 (2015). [2] A. Buck et al., Nat. Phys. 7, 543 (2011). [3] B. Hidding et al. Phys. Rev. Lett. 104, 195002 (2010).
27
High resolution phase contrast images of biological
specimens obtained from a 20TW laser
Bo Guo1, Xiao Hui Zhang1,2, Jie Zhang1,2, Chih-Hao Pai1, Jian Fei Hua1, Hsu-hsin Chu3, Jyhpyng Wang3, Wei Lu1*
1Department of Engineering Physics, Tsinghua University, Beijing 100084, China
2Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang 621900, China 3Department of Physics, National Central University, Jhong-Li 621, Taiwan
Betatron radiation emitted from relativistic electrons in the laser wakefield accelerators(LWFA) with high
brightness and micron size can be applied to phase contrast imaging [1][2]. But one of the main limitations of the
betatron x-ray source is the significant shot-to-shot fluctuations. A bright and stable x-ray source with
1.1×〖10〗^7 photons(>4keV) per shot based on a 20TW laser has been developed. We found a way to decrease
the shot-to-shot fluctuations by multiple shots accumulation and quantified the shot number required to ensure
the stability, while high quality phase contrast images with a contrast higher than 0.61 and a resolution better than
10μm of biological specimens with skins, bones and organs were obtained.
Figure 6. Phase contrast images of an about 1cm of butterfly and fish. Many details of head, skins, organs can be clearly seen.
References [1] S. Kneip et al. Appl. Phys. Lett. 99, 093701 (2011). [2] J. Wenz et al. Nat. Commun. 6,7568 (2015).
28
10GeV electron bunch in dual-stage all-optical laser
wakefield acceleration
V. B. Pathak1*, Hyung Taek Kim1,2, J. Vieira3, L. O. Silva3, and Chang Hee Nam1,4
1Center for Relativistic Laser Science,Institute for Basic Science (IBS), Gwangju 61005, Korea 2Advanced Photonics Research Institute,Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
3GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisbon, Portugal 4Department of Physics and Photon Science,GIST, Gwangju 61005, Korea
We propose an all-optical dual-stage laser wakefield acceleration (LWFA), staged with co-propagating two-
color laser pulses in a plasma medium, to enhance the electron bunch energy. The two-color dual-stage LWFA
can be understood as following: In the first stage, the leading lower frequency laser pulse excites a plasma wave
with a lower phase velocity, which triggers electron self-injection (injector stage). The second harmonic laser
pulse, trailing just behind the leading pulse, is guided within the bubble. Once the leading pulse is depleted, the
trailing second harmonic pulse excites a wakefield moving at a higher phase velocity, therefore increasing the
acceleration distance (accelerator stage). The leading part of the electron bunch, trapped and accelerated in the
injector stage, can be coupled into the accelerator and can then be further accelerated to the multi-GeV range. Due
to the higher frequency of the trailing laser pulse, the acceleration length of the second-stage can be significantly
enhanced. In this all optical dual-stage LWFA, the electrons can gain 3 times higher energy as compared to the
energy gain from the single stage LWFA driven by a single-color laser pulse with equivalent energy. Our multi-
dimensional particle-in-cell simulations demonstrate that a 10-GeV electron bunch with 20-pC charge can be
obtained by the two-color dual-stage LWFA using total input laser power of 0.6 PW
29
Stimulated Raman Backscatter from a laser
wakefield accelerator
Amina E. Hussein1*, K. Behm1, Y. Horovitz1, V. Chvykov1, A. Maksimchuk1, T. Matsuoka1, C. McGuffey2, A.G.R. Thomas1, V. Yanovsky1, K. Krushelnick1
1Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, MI, 48103, USA, 2Center for Energy Research,
University of California, San Diego, CA, 92093, USA *[email protected]
Experiments were performed using the HERCULES laser at the University of Michigan to produce the first
experimental measurements of backward Stimulated Raman Scattering (BSRS) generated by a 30 fs laser pulse
during laser wakefield acceleration. Backscattered radiation was found to be highly modulated and significantly
broadened and red-shifted in cases where electrons were generated. Backward SRS broadening (increased red-
shifting) was found to increase linearly with electron charge generation for laser intensities exceeding 100 TW.
The red-shifted area was also increased linearly with plasma density at these powers. No such correlations were
observed for laser powers at and below 50 TW. Red-shift broadening of the backward SRS spectrum may be
associated with increased electron-self injection due to perturbation of the plasma bubble in a wakefield
accelerator, resulting in a greater number of accelerated electrons.
30
Effect of plasma-wave topology on enabling high
precision HEP using a plasma-based collider
Aakash Sahai1*, Thomas Katsouleas2 , Andrei Seryi3
1Dept. of Physics & Johns Adams Institute for Accelerator Science, Imperial College London, South Kensington, London SW7 2AZ, UK
2Dept. of Physics, University of Virginia, Charlottesville, VA 29903, USA 3Johns Adams Institute for Accelerator Science & Dept. of Physics, Denys Wilkinson Building, Keble Road, Oxford, OX1
3RH, UK *[email protected]
In this work we for the first time unravel the constraints on the topology of a plasma-wave underlying the
acceleration stages of the plasma-based accelerator [1] for enabling high-precision exploration of high- energy
physics within and beyond the Standard model at the interaction point of a future plasma-based collider [2][3].
Using analytical theory and 3D PIC simulations we present a significant variation of the electromagnetic fields of
a plasma wave depending upon its geometry in comparison to the well- established models presently used in
plasma collider designs [2][3]. We show that the plasma wave geometry affects the ability of a linear collider
design [4] to address the symmetry violations that are maximally violated in the Standard Model, at the collider
interaction point. We show using a 3D PIC simulation based scaling law that the parameters of the plasma wave
geometry play a critical role in enabling high-precision HEP, vital for availing beams that would allow such
precision at the interaction point of a future plasma collider
References [1] W. Lu, et. al., A nonlinear theory for multidimensional relativistic plasma wave wakefields, Physics of Plasmas 13, 056709 (2006); doi: 10.1063/1.2203364 [2] A. Seryi, M. Hogan, S. Pei, T. Raubenheimer, P. Tenenbaum, T. Katsouleas, C.K. Huang, C. Joshi, W. B. Mori, P. Muggli, A concept of plasma wakefield acceleration linear collider (PWFA-LC), WE6PFP081, Proceedings of PAC09, Vancouver, BC, Canada [3] E. Adli, et. al., A Beam Driven Plasma-Wakefield Linear Collider: From Higgs Factory to Multi- TeV, SLAC-PUB-15426, arXiv:1308.1145 [4] The International Linear Collider Technical Design Report, Volume 2: Physics ILC-REPORT-2013-040, arXiv:1306.6352
31
Towards Exascale Simulations of Laser Plasma
Interaction
Michael Bussmann*, Joao Branco, Heiko Burau, Thomas E. Cowan, Alexander Debus, Marco Garten, Axel Huebl, Thomas Kluge, Alexander Matthes, Richard Pausch, Ulrich Schramm, Klaus Steiniger and
René Widera
Helmholtz-Zentrum Dresden – Rossendorf, Institute of Radiation Physics, Bautzner Landstrasse 400, 01328 Dresden *[email protected]
Simulations of Laser Plasma Interaction drive the field of laser-driven accelerators since its beginnings. Yet,
their predictive powers have been limited by several key aspects. First, many codes were and are still unable to
fully exploit the computational power available in modern supercomputers. This is both due to the fact that we
are facing a zoo of programming models and hardware architectures as well as to the fact that the main
algorithm, the particle-in-cell technique, is itself memory-bound and thus usually does not show peak
performance floating point capability.
Second, comparison to experimental results is limited both by the limited knowledge on key experimental
parameters as well as limited reproducibility in experiments. This means that in order to represent an experiment
by simulation one has to perform a parameter survey rather than a single simulation.
Third, comparison to experimental results must take into account the variation in input parameters to the
simulation, e.g. phase space distribution of macro-particles, numerical variations due to the choice of model, e.g.
Maxwell solver, and the variation in model predictions itself. Quantifying these variations via error bars requires
to increase parameter surveys even further.
Fourth, comparison to experimental results requires synthetic diagnostics that match the diagnostics used in
the experiment as best as possible, since many diagnostics measure plasma properties via indirect processes that
should be included in deriving results from simulation, e.g. K-alpha radiation as a measure for temperature.
Finally, open standards are mandatory for creating reproducible results, thus open file formats, open source
codes and even open data are key requirements to foster progress of the research field.
We emphasize that all these prerequisites for predictable simulations demand computational power beyond
what is available now, both in simulation and (subsequent) data analysis. Yet, with increasing experimental
diagnostic capabilities and experimental control comparison to experiment becomes critical for optimizing laser
plasma acceleration both in performance and robustness. We will thus show possible steps towards Exascale
particle-in-cell simulations and data analysis using recent results on laser particle acceleration as illustrative
examples.
32
Burst of Ultraintense, Coherent Radiation from
Colliding Laser Pulses in a Plasma
Min Sup Hur*
Department of Physics, Ulsan National Institute of Science and Technology, Ulsan 44910, Korea *[email protected]
While it is widely accepted that the plasma oscillation is an underlying mechanism of coherent radio-burst in
space, there has been a controversy on the radiation at the plasma frequency in laser-plasma interaction in
laboratory. Commonly accepted framework is that since the plasma oscillation is electrostatic, its electric field is
curl-free, prohibiting any electromagnetic radiation. On the other hand, numerous theoretical, experimental,
simulation data suggests a possibility of the radiation burst by the plasma oscillation. However, all the previous
reports of radiation by the plasma oscillation have shown broadband spectrum, making it dubious if it is really
from the self-oscillation of the plasma with wp. In this presentation, for the first time we show theoretical and
simulation results of radiation burst with a narrowband spectrum at the plasma frequency. The mechanism is
colliding two detuned laser pulses in a plasma. In the overlapped region of the laser pulse, the electrons are trapped
in the ponderomotive potential train associated with the beat of the laser pulses. Because the overlapped region is
spatially limited to a few microns, a finite-sized electron block composed of multiple microbunches trapped in
the ponderomotive buckets are displaced in-phase. After the pulse collision is finished, the displaced electron
block commence the plasma oscillation, named plasma dipole oscillation (PDO). As the PDO is located close to
the plasma-vacuum boundary, it emits strong THz burst into the vacuum side, exhibiting a narrowband spectrum
at the plasma frequency and GV/cm-order peak electric field. Emitted energy of the burst reaches mJ, with
efficiency of order 10-3. We observe that non-zero curl of the electric field is generated over the collisional
position of the laser pulses, which is quite opposite to conventional belief that laser-induced plasma oscillation is
purely electrostatic, or contains at most a very negligible electromagnetic, coherent component.
33
Numerical studies of density transition injection in
laser wakefield acceleration
F. Massimo1*, A. F. Lifschitz1, C. Thaury1 and V. Malka1,2
1Laboratoire d’Optique Appliquée, ENSTA ParisTech - CNRS UMR 7639, École Polytechnique, Université Paris-Saclay, 828 Boulevard des Maréchaux - 9172, Palaiseau Cedex, France
2Department of Physics and Complex Systems, Weizmann Institute of Science, Rehovot, 76100, Israe *[email protected]
The quality of laser wakefield accelerated electrons beams is strongly determined by the physical mechanism
exploited to inject electrons in the wakefield. One of the techniques used to improve the beam quality is the density
transition injection, where the electron trapping occurs as the laser pulse passes a sharp density transi-tion created
in the plasma. Although this technique has been widely demonstrated experimentally, the literature lacks
theoretical and numerical studies on the effects of all the transition parameters and of the laser parame-ters. We
thus report and discuss the results of a series of PIC simulations where the density transition height and downramp
length are systematically varied, to show how the electron beam parameters and the injection mechanism are
affected by the density transition parameters. The effects of different laser pulse power on the injection process
are also shown.
Figure 1. Snapshots of electron density ne illustrating shock-front injection
34
Plasma wakefield excitation by a bunched proton
beam
Konstantin Lotov*
Budker Institute of Nuclear Physics SB RAS, 630090 Novosibirsk, Russia Novosibirsk State University, 630090 Novosibirsk, Russia
Proton beams are perspective drivers for plasma wakefield acceleration because of their high energy content.
However, a large length of available proton bunches requires them to be micro-bunched either by an external
system, or by the plasma itself. The plasma creates the micro-bunches through the self-modulation instability,
which, if properly controlled, ensures the optimal spacing of the micro-bunches [1]. However, roughly three
quarters of the initial beam charge are lost during this process, so the plasma bunching is inefficient. Pre-
bunching by an external system can be more charge efficient [2], but produces equally spaced bunches, while
the micro-bunch charge can vary according to the charge distribution in the initial proton bunch.
We study wave excitation by equally spaced micro-bunches that form the bunch train. If the bunches are
spaced at exactly the plasma frequency, then later bunches are partly defocused by the wakefield of earlier ones,
and the train as a whole is unstable. The optimum bunch-to-bunch distance depends on the bunch number in the
train. Consequently, by simply adjusting the train period, we cannot put all bunches to favorable phases
simultaneously. By varying the bunch charge, however, it is possible to reach the optimum positioning of the
micro-bunches with respect to the plasma wave. The optimum distribution of the bunch charge is exponential,
and the exponent depends on the difference between the plasma wavelength and the train period. The leading
front of the initial Gaussian beam can be, to some extent, approximated by the exponent. Therefore, for any initial
proton bunch there exists an optimum difference between the plasma wavelength and the train period, which
maximizes the excited wakefield. For the optimized micro-bunch train prepared from the SPS 400 GeV proton
beam, the energy gain of accelerated electrons can be as high as 150 GeV in the plasma of the density 7 1014cm-3
References [1] K.V.Lotov, Phys. Plasmas 22, 103110 (2015). [2] I. Sheinman, A. Petrenko, Proc. RuPAC2016, St. Petersburg, Russia, p.303-306.
35
Laser acceleration of charged particles from low-
density targets
V. Yu. Bychenkov1,2*
1P. N. Lebedev Physics Institutes, Russian Academy of Sciences, Moscow 119991, Russia,
2Center for Fundamental and Applied Research, VNIIA, ROSATOM, Moscow 127055, Russia *[email protected]
Laser-driven particle acceleration by femtosecond high-power pulses is a topic of extraordinary interest for
fundamental research and possible applications. These issues motivated a worldwide search for different
mechanisms of electron and ion acceleration with the aim to maximize both the yield and the energy of the
generated particles. In this context, an important role is played by low-density targets with an electron density
close to the relativistic critical density that is discussed here, mainly on the basis of the 3D particle-in-cell (PIC)
simulations.
We have extended recently published results of so-called SASL (synchronized acceleration by slow light)
simulations [1] to other schemes of laser-plasma interaction for proton acceleration involving manipulation of
laser polarization and low-density targets which are available in practice. In all cases, the main idea is to capture
the protons from a target front side in laser pulse ponderomotive electric field sheath and keep them
synchronized with the latter due to specific nonlinear propagation and laser-target design. This is illustrated in
Figure 1.
Figure 7. Synchronized motion of a laser pulse and a proton bunch: positions, x(t), of the laser pulse front (gray) and the front of the accelerated proton bunch (black) inside a target
The 3D PIC simulations have also demonstrated effective acceleration of electrons from low-density targets
in terms of the increased electron yield. The electron charge per shot with energies in excess of 30 MeV reaches
multi/multi-tens nC level for current femtosecond lasers that is hard-to-reach with gaseous or solid-density
targets and constitutes an important step to a deep gamma-radiography based on laser-driven high-energy
electrons.
36
This work was supported by the Russian Science Foundation (Grant No. 17-12-01283).
References [1] A. V. Brantov, E. A. Govras, V. F. Kovalev, and V. Yu. Bychenkov, Phys. Rev. Lett. 116, 085004 (2016).
37
Particle-in-cell simulations of laser-plasma
interactions at solid densities and relativistic
intensities: the role of atomic processes
D. Wu*
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, 201800 Shanghai, China
A direct study of intense laser-solid interactions is still of great challenges, because of the many coupled
hysical mechanisms, such as direct laser heating, ionization dynamics, collision among charged particles, and
electrostatic or electromagnetic instabilities, to name just a few. Here, we present a full particle-in-cell simulation
(PIC) framework, which enables us to calculate laser-solid interactions in a “first principle” way covering almost
“all” the coupled physical mechanisms [1-2]. Apart from the mechanisms above, the numerical self-heating of
PIC simulations, which usually appears in solid-density plasmas, is also well controlled by the proposed “layered-
density” method. This method can be easily implemented into the state-of-the-art PIC codes.
The electron heating/acceleration at relativistically intense laser-solid interactions in the presence of large
scale pre-formed plasmas [3-5] is re-investigated by this PIC code. Results indicate that collisional damping (even
though it is very week) can significantly influence the electron heating/acceleration in front of the target.
Furthermore, the Bremsstrahlung radiation will be enhanced by 2~3 times when the solid is dramatically heated
and ionized. For the considered case, where laser is of intensity 1020 W/cm2 and pre-plasma in front of the solid
target is of scale-length 10 μm, collision damping coupled with ionization dynamics and Bremsstrahlung
radiations is shown to lower the “cut-off” electron energy by 25%. In addition, the resistive electromagnetic fields
due to Ohmic-heating also play a non-ignorable role and must be included in real laser-solid interactions.
References [1] D. Wu, X. T. He, W. Yu, and S. Fritzsche, Phys. Rev. E 95, 023208 (2017). [2] D. Wu, X. T. He, W. Yu, and S. Fritzsche, Phys. Rev. E 95, 023207 (2017). [3] D. Wu, S. I. Krasheninnikov, S. X. Luan, and W. Yu, Phys. Plasmas 23, 123116 (2016). [4] D. Wu, S. I. Krasheninnikov, S. X. Luan, and W. Yu, Nucl. Fusion 57, 016007 (2017). [5] D. Wu, S. X. Luan, J. W. Wang, W. Yu, J. X. Gong, L. H. Cao, C. Y. Zheng and X T He, Plasma Phys. Control. Fusion 59, 065004 (2017).
38
Physical Mechanism of the Intrinsic Transverse
Instability in Laser Pressure Ion Acceleration
Y. Wan1,2,3, C.-H. Pai1, C. J. Zhang1, F. Li1, Y. P. Wu1, J. F. Hua1, W. Lu1,3,*, Y. Q. Gu3, L. O. Silva4, C. Joshi5, and W. B. Mori5
1Department of Engineering Physics, Tsinghua University, Beijing 100084, China
2Laser Fusion Research Center, China Academy of Engineering Physics, Mianyang, Sichuan 621900, China 3IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, China
4GoLP/instituto de Plasmas e Fusao Nuclear, Instituto Superior Tecnico, Universidade de Lisboa, 1049-001 Lisboa, Portugal
5University of California Los Angeles, Los Angeles, California 90095, USA *[email protected]
With the rapid progress of ultraintense lasers, strong interests have been aroused on “light sail” and “flying
mirror” concept driven by laser pressure, which may lead to useful applications such as laser pressure driven ion
acceleration (RPA). However, many simulations indicated that such “light sail/flying mirrors” may suffer
instabilities that can break up their surfaces. With intense research for more than a decade, the physical mechanism
behind these instabilities has not been clarified. In this work, a theoretical model has been developed to decipher
this mystery. It turns out that the ripples on the foil surface are mainly induced by the coupling between the
transverse oscillating electrons and the quasi-static ions. The predictions of the mode structure and the growth
rates from the theory agree well with the results obtained from the PIC simulations in a wide range of parameters,
indicating the model contains the essence of the underlying physics of the transverse breakup of the foil. Based
on the above analysis, a new ion acceleration scheme and companied 2/3D simulations are also presented to avoid
this big problem and achieve high quality high energy ion beams, which may open up a new route for compact
laser trigger ion sources.
39
Ultrafast ion-induced dynamics in borosilicate glass
M. Coughlan1*, L. Senje2, M. Taylor1, G. Nersisyan1, D. Jung1, H. Donnelly1, N. Breslin1, M. Zepf1,3 and B. Dromey1
1Department of Physics and Astronomy, Queen’s University Belfast, Belfast, United Kingdom
2Department of Physics, Lund University, P.O. Box 118, S-221 00 Lund, Sweden 3Helmholtz-Institut Jena, D-07743 Jena, Germany
Understanding the effects of ion interactions in condensed matter has been a focus of research for decades.
Many of these studies focus on the longer term effects such as cell death or material integrity and this is
typically performed using relatively long (>100 ps) proton pulses from radiofrequency accelerators in
conjunction with chemical scavenging techniques [1]. Recently, measurements of few-picosecond pulses of
laser driven protons have been performed via observation of transient opacity induced in SiO2 [2], in this work,
the ultrafast response of the material can be understood by the rapid formation of self-trapped excitonic states on
the order of 150 fs.
Here the onset and evolution of an ion-induced opacity is examined in borosilicate glass (BK7). It is found
that the duration of the opacity is several orders of magnitude greater than the duration of the proton pump pulse
that was measured in SiO2 and the underlying processes which may be affecting this extended recovery are
discussed.
References [1] G. Baldacchino, Radiation Physics and Chemistry, 77, 1218-1223 (2008). [2] B.Dromey, et al. Nature Communications, 7, 10642 (2016).
40
Electron solvation dynamics in H2O during ultrafast
pulsed ion radiolysis
B. Dromey1*, L. Senje2, M. Coughlan1, H. Donnelly, N. Breslin, G. Nersisyan1, C. L. S. Lewis1, C.-G. Wahlström2, M. Zepf1,3
1School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, United Kingdom
2Department of Physics, Lund University, P. O. Box 118, S-221 00 Lund, Sweden 3Helmholtz-Institut Jena, D-07743 Jena, Germany
Beams of energetic ions are finding application in multiple cutting edge technologies ranging from
hadrontherapy to semiconductor device manufacture/metrology. To date, however, ion interactions in matter have
been dealt with in a manner similar to those of electrons/photons, with attention primarily being paid to the energy,
E, lost over path length, dx, giving the stopping power S(E) = - dE/dx. The obvious distinction is of course that
ion stopping in matter exhibits a Bragg peak. In both scenarios the expected cell death or material damage are
then generally extrapolated from empirical studies of dose deposition. For ions it is not immediately clear that this
is the correct approach as it masks a critical phase of the interaction. When ions are incident on matter they
generate dense tracks of ionisation that rapidly evolve. Exactly how this evolution, which occurs on femtosecond
and picosecond times, determines the nascent radiation chemistry is still largely unknown.
Recently we have demonstrated that laser driven ion accelerators can provide an ultrafast tool for studying
this inherently multiscale regime with temporal resolution < 0.5 ps [1,2]. Here we present novel results that show
a marked difference in the solvation time of electrons generated due to the passage of fast electrons/X-rays and
protons (~3 MeV) in water. The solvation time is shown to dramatically increase from < 5 ps for a < 1 ps pulse
of fast electrons/X-rays to > 190 ps for a 22 ± 3 ps (Fig 1 a, b) pulse of protons. We discuss the role of nano-
cavitation during ion radiolysis in H2O and how this can lead to the increased time for the solvation of the electron.
Figure 8. Ultrafast solvation dynamics of the electron for pulse ion radiolysis in H2O
References [1] B. Dromey, et al., Nat.Comms.,4, 1763 (2013) [2] L. Senje, et al., App. Phys. Letts., 110, 104102 (2017)
41
Development of laser-solid plasma accelerators for
industrial imaging and nuclear inspection
applications
Ceri Brenner1, Chris Armstrong1,2, Dean Rusby1,2, Graeme Scott1, Chris Jones3, Seyed Mirfayzi4, Paul
McKenna2, Satya Kar4, John Jowsey5, Tom Scott3 and David Neely1
1STFC Central Laser Facility, Rutherford Appleton Laboratory, Harwell Campus, OX11 0QX, UK
2Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK 3Interface Analysis Centre, HH Wills Physics Laboratory, Tyndall Avenue, Bristol, BS8 1TL, UK
4Centre for Plasma Physics, Queen’s University Belfast, Belfast BT7 1NN, UK 5Ground Floor North B582, Sellafield Ltd, Seascale, Cumbria CA20 1PG, UK
Laser-accelerated electrons with relativistic energies and mega-Amp current injected into solid targets can
generate bright, energetic, point-like photon and particle sources. High-energy beams of x-rays, ions and neutrons
that are generated as a result are of particular interest for industrial applications as the laser-accelerator concept
has several major competitive advantages, namely that it can generate x-rays from a micro-scale point source for
high resolution projection radiography and can operate in multi-modal delivery generating, in parallel, beams of
electrons, neutrons, positrons and even muons for complimentary inspection techniques. This makes a laser-
accelerator a versatile source, capable of imaging and inspecting a wide range of samples and materials that are
of interest to many high value sectors – from medium density alloys for aerospace through to large dense objects
such as nuclear waste barrels.
Recent results in the development of x-ray, ion and neutron beams for these specific applications will be
discussed. Advanced targetry for generating micro x-ray sources and cryotargets for new acceleration dynamics
in deuterium beams will be presented. A new 3-year STFC-funded Innovation Partnership Scheme project that
started in October 2016 will also be introduced. The collaboration will demonstrate and develop laser-driven x-
ray and neutron beams for nuclear waste inspection in partnership with Sellafield Ltd, the UK’s nuclear waste
decommissioning authority.
With the recent delivery of the CLF’s 100 J, 10 Hz DiPOLE100 laser system and the development of LLNL’s
10 Hz HAPLS system, utilising these beams for industrial applications is now within reach. This step-change in
high-energy laser technology is vital for realising laser accelerators for important and high impact applications
and for transferring the technology from laboratory to commercial exploitation.
42
Rapid and uniform heating of matter with a laser-
driven quasimonoenergetic aluminum ion beam
W. Bang1* , B. J. Albright2 , P. A. Bradley2, D. C. Gautier2, S. Palaniyappan2, E. L. Vold2, M. A. Santiago Cordoba2, C. E. Hamilton2, and J. C. Fernández2
11 Department of Physics and Photon Science, GIST, Gwangju 61005, Korea
2 Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. *[email protected]
On the Trident laser facility at Los Alamos National Laboratory, we have used a beam of laser-driven quasi-
monoenergetic aluminum ions [1] to heat solid density gold and diamond foils uniformly and rapidly above
10,000 K [2]. Although matter at such an extreme state, known as warm dense matter, is commonly found in
astrophysics (e.g., in planetary cores) as well as in high energy density physics experiments, its properties are
difficult to predict theoretically and are not well understood. A sufficiently large warm dense matter sample that
is uniformly heated would be ideal for these studies, but has been unavailable to date. For the first time, we
visualized directly the expanding warm dense gold and diamond with an optical streak camera [3]. We developed
a new technique to determine the initial temperature of these heated samples from the measured expansion speeds
of gold and diamond into vacuum [4]. We anticipate the uniformly heated solid density target will allow for direct
quantitative measurements of equation-of-state, conductivity, opacity, and stopping power of warm dense matter,
benefiting plasma physics, astrophysics, and nuclear physics.
Figure 9. Schematic layout of the experimental setup (not to scale)
References [1] S. Palaniyappan, C. Huang, D. C. Gautier, C. E. Hamilton, M. A. Santiago, C. Kreuzer, A. B. Sefkow, R. C. Shah, and J. C. Fernandez, Nat. Commun. 6, 10170 (2015). [2] W. Bang, B. J. Albright, P. A. Bradley, E. L. Vold, J. C. Boettger, and J. C. Fernández, Phys. Rev. E 92, 063101 (2015).
43
[3] W. Bang, B. J. Albright, P. A. Bradley, D. C. Gautier, S. Palaniyappan, E. L. Vold, M. A. S. Cordoba, C. E. Hamilton, and J. C. Fernández, Sci. Rep. 5, 14318 (2015). [4] W. Bang, B. J. Albright, P. A. Bradley, E. L. Vold, J. C. Boettger, and J. C. Fernández, Sci. Rep. 6, 29441 (2016).
44
Proton acceleration from the interaction of a PW-
class laser and a solid hydrogen ribbon
D. Margarone*
ELI-Beamlines, Institute of Physics (ASCR), Prague, Czech Republic *[email protected]
The interaction of a high power laser and a pure hydrogen target has advantages from the experimental point
of view in terms of plasma characterization, as well as for a potentially use at high repetition rates since such
target is essentially debris free.
A cryogenic hydrogen ribbon (75-100µm thick) was irradiated with the VULCAN-PW laser (0.6 kJ/1ps) at
the RAL facility. High current proton beams with energies exceeding 50 MeV were accelerated into both
directions (forward and backward with respect to the incoming laser beam). The energy coupling into energetic
protons was very high in comparison to standard plastic foils. This is linked to the laser absorption along the
overall target thickness, which is strongly enhanced as confirmed by particle-in-cell simulations.
Such results are very promising for future multidisciplinary applications of laser driven proton beams, e.g.
hadrontherapy, both due to high purity and high proton beam charge per laser pulse, as well as technological
advantages coming from the debris free nature of the used target.
References [1] D. Margarone et al., Phys. Rev. X 6 (2016) 041030
45
Laser-Driven MeV Argon Ion Beam Generation with
Narrow Energy Spread
Jiancai Xu*, Tongjun Xu, Baifei Shen*, Hui Zhang, Shun Li, Yong Yu, Jinfeng Li, Xiaoming Lu, Cheng Wang, Xinliang Wang, Xiaoyan Liang, Yuxin Leng, Ruxin Li, and Zhizhan Xu.
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of
Sciences, P. O. Box 800-211, Shanghai 201800, China *[email protected] and *[email protected]
Abstract: Here we report a highly collimated, narrow-energy-spread argon(Ar16+) ion beam with minimum
absolute energy spread of 0.19 MeV/u, is experimentally produced by a 45fs ultra-intense laser pulse interacting
with clustering argon gas target. A novel mechanism proposed based on PIC simulation well explains the
experimental observation and gives an energy scaling to GeV for argon ion beam.
Laser driven particle acceleration shows a remarkable progress in generating multi-GeV electron bunches and
10’s of MeV ion beams based on ultra-short super-intense laser facility. High-energy laser pulse offers
acceleration field of TV/m, several orders of magnitude higher than that in conventional accelerators, enabling
compact devices. Here we report on an experimental result that a highly collimated argon ion beam (Ar16+) with
narrow energy spread has been produced by a 45fs ultra-intense laser pulse interacting with a clustering argon gas
target. The observed argon ion beams have a minimum absolute energy spread of 0.19 MeV per nucleon [1]. The
generated ion beam offers a high-quality injector for conventional ion accelerators.
We identify a novel scheme of the high-quality ion beam generation, based on two-dimensional particle-in-
cell (PIC) simulations. High-energy argon ion beam with narrow energy spread was also observed. It is found that
there are two distinct stages for in the argon ion acceleration process, i.e. Coulomb explosion and ion spectrum
modulation. In the first stage, the intense laser field induces Coulomb explosion of the argon clusters in its focus
volume, and the ions get energy gain mainly from the cluster explosion and have a flat continuous spectrum. In
the second stage, the laser wakefield modulates the ion spectrum and significantly reduces the energy spread. The
proposed mechanism well explains our experimental observation and gives an energy scaling up to GeV for high-
quality argon ions.
Based on this novel regime, laser-cluster interaction has an ability to provide ions of more species including
Xe, Kr, C, O, N, and so on, from noble-gas cluster as well as molecules cluster. Moreover, the cluster-gas target
is able to work on a high repetition rate. Since the 10Hz PW laser facility is in progress, the reproducible high-
quality ion source will become more feasible for many applications in near future, including medical therapy,
fusion targets diagnostics, nuclear physics, and injector of ion accelerators.
References [1] Jiancai Xu et al., Laser-driven MeV argon ion beam generation with narrow energy spread.
46
Recent Progress of Laser Ion Acceleration at Peking
University
Chen Lin*, Yixing Geng, Qing Liao, Yinren Shou, Wenjun Ma, Xiaohan Xu, Minjian Wu, Dongyu Li, Jungao Zhu, Haiyang Lu, Yanying Zhao, Jiaer Chen and Xueqing Yan
State Key Laboratory of Nuclear Physics and Technology and CAPT, Peking University, Beijing 100871, China
A proton-type of compact laser driven proton accelerator (CLAPA) has recently been built at Peking
University. We present the generation of stable proton beams in the experiments of high intensity (8.3*1019
W/cm2) laser pulses irradiating on home-made sub-micrometer thick plastic targets. The temporal contrast of the
laser pulse was 1010 at 100 ps before the main pulse with a cross-polarized wave (XPW) system, and no plasma
mirror was used in our system. The maximum proton energy exceeded 15 MeV when using 1.2 m plastic targets.
Stable proton beams with energy higher than 8.5 MeV were also detected with 20 nm thick plastic targets. By
improving the target surface flatness and the laser-target spatial coupling accuracy, the shot to shot stability of
proton cutoff energy was better than 3%.
47
Interaction of a Petawatt femtosecond laser with
near-critical-density plasma
P. K. Singh,1* J. H. Shin,1 H. T. Kim,1,2 J. H. Jeon,1 I. W. Choi,1,2 V. B. Pathak,1 C. M. Kim,1,3 S. K. Lee,1,2 J. H. Sung,1,2 H. W. Lee,1 Y. J. Rhee,1 C. Aniculaesei,1 K. H. Pae,1,2 M. H. Cho,1 J. Y. Yoo,1 C. Hojbota,1,3
S. G. Lee,1,3 K. Nakajima1, & C. H. Nam1,3
1Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 61005, Republic of Korea 2Advanced Photonics Research Institute, GIST, Gwangju 61005, Republic of Korea
3Department of Physics and Photon Science, GIST, Gwangju 61005, Republic of Korea *[email protected]
The rapid advancements in the area of intense ultrashort lasers have made it possible to recreate terrestrial
physical conditions in laboratory [1]. Exotic astrophysical phenomenon can be demonstrated on a much smaller
spatial and temporal scale by focusing intense ultrashort laser pulses into a medium to achieve high energy density
[2]. Near critical density targets are one such medium where an ultrahigh intensity laser can create a long channel
of strongly heated particles [3]. The rapid heating of the medium can lead to the formation of shock wave, which
can accelerate background ion species to high energy [4].
Here, physical phenomena behind the interaction of petawatt intense femtosecond laser pulses (I20 2~ 1 10 W/cm× ) with near critical density plasma (ne = 3×1020 cm-3) will be discussed. Measured kinetic energy
spectrum of transverse ions (shown in Fig. 1(a)) and forward electrons, corroborate with the observed plasma
structure. The plateau structure observed in the proton spectra (Fig. 1(a)), indicate an evidence of electrostatic
shock acceleration [4]. Moreover, in low energy range (< 0.3 MeV), the presence of order of magnitude higher
flux of He+ compared to that of He++ reveals the charge exchange process occurring in an extended gas medium.
Furthermore, a plasma emission diagnostic in the optical regime shows pronounced Raman scattering (Fig. 1(b))
along the backward and the transverse directions. For higher plasma density (ne = 3×1020 cm-3), the modulated
Raman scattered signal is linked with the filamentation of a laser beam during its propagation in the near-critical
density plasma. The space and time-resolved optical shadowgrams reveal complex interplay of plasma density
and laser intensity. The experimental observations are also corroborated by 2D particle-in-cell simulations. In
summary, findings of the present study highlight the important role of near-critical density plasmas in particle
acceleration, growth of electrostatic instability and advancements of laboratory astrophysics.
48
Figure 10. (a) Retrieved spectra of He+, He++ and protons as a function of energy per charge. (b) Plasma emission spectra recorded at two different plasma densities, showing a modulated Raman signal at the high density.
References [1] B. A. Remington et al., Science 284, 1488 (1999). [2] B. A. Remington, Plasma Phys. Control. Fusion 47, A191 (2005). [3] G. S. Sarkisov et al., Phys. Rev. E 59, 7042(1999). [4] M. S.Wei et al., Phys. Rev. Lett. 93, 155003 (2004).
49
DD fusion neutron generation from low energy, fs-
laser interaction with free flowing D2O
Jungmoo Hah*, John Nees, Karl Krushelnick, and Alec Thomas
Center for Ultrafast Optical Sciences, University of Michigan, Ann arbor MI, 48109, USA *[email protected]
Laser-Plasma Interactions (LPI) in relativistic regime can generate and accelerate high energy charged
particles. These high-energy particles collide each other and trigger nuclear fusion reaction resulting in neutron
production. Due to the advance in laser technology, km-size of particle accelerators shrink down to a table-top
scale laser based particle accelerator.
Here we demonstrate heavy-water based neutron source. Using several-mJ energy pulses from a high-
repetition rate (½ kHz), ultrashort (35 fs) pulsed laser interacting with a ∼ 10 μm diameter stream of free-flowing
heavy water (D2O), we get a 2.45 MeV neutron flux of 105/s. In the intentionally generated pre-plasma, laser
pulse energy is efficiently absorbed, and energetic deuterons are generated [1]. As laser pulse energy increased
from 6mJ to 12mJ, the neutron flux increased. From the 2D particle-in-cell simulation, comparable neutron fluxes
are shown at the similar laser characteristics to the experiment. Also, simulation shows forward and backward
moving deuterons, which are main distributing ions impinging upon D2O stream and vapor, respectively.
Figure 11. [Left] Neutron-ToF result from H2O and D2O target. Right] Neutron flux is measured (blue shaded region) by neutron bubble detectors and 2D PIC simulation (line plots) shows most of neutrons are generated
from backward moving deuteron.
References [1] J. T. Morrison et al., Phys. Plasma 22, 043101 (2015).
50
Enhancing betatron radiation in laser wakefield
accelerators
K. Krushelnick, T. Zhao, K. Behm, A. Hussein, C. McGuffey, V. Chvykov, B. Hou, A. Maksimchuk, V. Yanovsky, A.G.R. Thomas
Center for Ultrafast Optical Science, University of Michigan Ann Arbor, Michigan USA 48109
Experiments were conducted using the Hercules laser facility at the University of Michigan to enhance the
production of synchrotron x-rays from the motion of electron beams in a laser wakefield accelerator. Various
methods were used to enhance the x-ray emission such as plasma length, density gradients, laser beam profile and
laser beam phase front. The x-rays were then used for absorption spectroscopy of heated materials
51
High-energy X/Gamma ray source from Compton
scattering and Bremsstrahlung in a self-modulated
Laser Wakefield Accelerator
N. Lemos1*, F. Albert1, J. Shaw2, P. M. King3, A. Milder2, K.A. Marsh4, A. Pak1, C. Joshi4
1Lawrence Livermore National Laboratory, NIF and Photon Sciences, 7000 East Avenue, Livermore, California 94550, USA 2Laboratory for Laser Energetics, 250 E River Rd, Rochester, New York 14623, USA
3Department of Physics, University of Texas at Austin, Austin, TX 78712, U.S.A. 4Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA
Understanding material properties under extreme conditions of temperature, pressure, and density is
essential for different fields of physics such as astrophysics, High Energy Density Science (HEDS) and Inertial
Confinement Fusion. The development of directional, low-divergence, and short-duration (ps and sub-ps) x-ray
probes with energies of tens of keV is desirable for these applications. Such high-energy x-ray probe beam
could be used to radiograph the imploding inertially-confined fusion capsule at the National Ignition Facility [1]
or warmdense matter created using lasers or Z-pinches via absorption spectroscopy or scattering techniques. It
was recently shown that using the kJ-class, short lasers present in most HEDS facilities, Self-Modulated Laser
Wakefield Acceleration (SMLWFA) [2,3] can generate a directional short-duration x-ray source with high-
brightness and critical energies up to 20 keV.
In this work, we generate an even more energetic source of x/Gamma-rays using the high charge relativistic
electron beam from a SMLWFA exploring two different mechanisms: Bremsstrahlung [5] and inverse Compton
scattering [6]. We focused the Titan short laser pulse (150J, 1ps) beam into a gas jet to produce a low divergence
electron beam with energies up to 300 MeV and 6 nCs of charge. The electron beam and the remaining laser pulse
then exited the gas jet and collided with a foil that was placed after the gas jet. When using a low Z foil the laser
collision with the foil created a plasma mirror that reflected the laser beam back to interact with the accelerated
electron beam and generated a bright, multi-keV x-ray beam via inverse Compton scattering. When using a high-
Z material foil, the electron beam generated a bright Gamma-ray beam through Bremsstrahlung. This x-ray beam
is an ideal probe and backlighter for time-resolved spectroscopy, imaging, and Compton radiography.
Experimental characterization of these two x/Gamma ray sources will be presented.
References [1] Hurricane O A, et al 2014 Nature 506 343–8 [2] Modena A et al 1995 Nature 377 606–8 [3] N. Lemos, et al, Plasma Phys. Controlled Fusion 58, 034018 (2016) [4] F. Albert, N. Lemos et al, Phys. Rev. Lett. 118, 134801 (2017) [5] Glinec Y et al, Phys. Rev. Lett. 98 194801 [6] Phuoc K T et al, Nat. Phot. 6,308–311 (2012)
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under the
52
contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC
53
Experimental observation of strong radiation
reaction effects in the interaction of a high-
intensity laser with a wakefield-accelerated electron
beam
E. Gerstmayr1*, J. M. Cole1, K. Behm2, T. G. Blackburn3, J. Wood1, C. D. Baird4, M. J. Duff5, C. Harvey3, A. Ilderton3,6, K. Krushelnick2, S. Kuschel7, M. Marklund3, P. McKenna5, C. D. Murphy4, K. Poder1, C.
Ridgers4, G. M. Samarin8, G. Sarri8, D. Symes9, A. G. R. Thomas2, J. Warwick8, M. Zepf7,8, Z. Najmudin1, S. P. D. Mangles1
1The John Adams Institute for Accelerator Science, Imperial College London, London, SW7 2AZ, UK
2Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109-2099, USA 3Department of Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
4York Plasma Institute, Department of Physics, University of York, York, YO10 5DD, UK 5SUPA Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK
6Centre for Mathematical Sciences, Plymouth University, UK 7Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität, 07743 Jena, Germany 8School of Mathematics and Physics, The Queen’s University of Belfast, BT7 1NN, Belfast, UK
9Central Laser Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, UK *[email protected]
We report on an experiment performed at the dual 300 TW Astra-Gemini laser of the Central Laser Facility
(UK) in 2015, colliding a highly relativistic electron bunch produced by laser wakefield acceleration (≈550 MeV)
with a very intense laser pulse (a0 ≈ 10) to probe radiation reaction. The electron and the gamma-ray spectra from
inverse Compton scattering were measured simultaneously and used to infer the conditions at the point of
interaction independently. This method allows us to take into account the variation of the intensity at the collision
due to the intrinsic fluctuations of the laser wakefield accelerator. Comparisons with several models show that
only those including strong radiation reaction are able to bring both measurements into agreement. In addition,
our results indicate some tension between quantum and classical models. The gamma-ray spectrum reached a
critical energy of over 30 MeV, which is significantly higher than the energies reported in previous inverse
Compton scattering experiments using laser-wakefield acceleration [1,2,3].
References [1] K. Ta Phuoc et al., Nature Photonics 6, 308 (2012) [2] N. D. Powers et al., Nature Photonics 8, 28 (2014) [3] G. Sarri et al., Physical Review Letters 113, 1 (2014)
54
Enhancement of betatron X/γ-rays in a laser plasma
accelerator
Liming CHEN1,2*, Yong MA1, Kai HUANG1,Wencao YAN1, Jie ZHANG1,2
1Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2 Key Laboratory for Laser Plasmas (MOE) and IFSA Collaborative Innovation center, Shanghai Jiao Tong University,
Shanghai 200240, China * [email protected]
Hard x-rays from fs laser produced plasmas have a number of interesting applications in the dynamic probing
of matter and in medical/biological imaging. Betatron radiation is a highly collimated laser-driven hard x-ray
source with fs duration which generated by electron transversely oscillation during acceleration in underdense
plasmas. We will summarize our recent progress in enhancing the betatron x-ray sources.
1) A new method is demonstrated for generating intense betatron x-rays using a clustering gas target irradiated
with an ultra-high contrast laser of 3 TW only [1]. The yield of the Ar x-ray betatron emission has been measured
to be 2×108 photons/pulse. Simulations point to the existence of clustering as a contributor to the DLA mechanism,
leading to higher accelerated electron charge (x40) and much larger electron wiggling (~8 μm) amplitudes in the
plasma channel, thereby finally enhancing the betatron x-ray photons.
2) Another concept of generation of bright betatron radiation during electron acceleration was newly invented
[2]. Two electron bunches with different qualities were injected sequentially into the wakefield driven by a super-
intense laser pulse. The first one is a mono-energetic electron bunch with peak energy of GeV level, and the
second one is injected continuously with large charge and performs resonantly transverse oscillation with large
amplitude during the subsequent acceleration, which results in the enhancement of betatron x-ray emission. After
optimize interaction conditions, -rays with yield reaches to 1010 can be obtained by using 200TW laser [3].
3) In order to control the stability of betatron x-ray generation as well as enhance its yield and energy,
ionization injection with N2 gas is studied. We obtained stably accelerated monoenergetic electron beams with
energy spread 5% for the first time [4]. 109 photons in hard x-rays and 108 photons in -rays are stimulated,
results in a peak brightness 1023 phs/s/mm2/mrad2/(0.1%BW). Quick injection, acceleration and oscillation in
the wake of the ionization injected electron leads to the effective resonant betatron oscillation, which result in -
ray photon energy and peak brilliance beyond that of 3rd generation synchrotron facilities [5]. Finally, an overall
comparison is done for the laser-driven Betatron and Inverse Compton Scattering sources.
References [1] L. M. Chen et al, Sci. Reports 3, 1912(2013) [2] W. C. Yan et al, PNAS 111, 5825(2014); Y. Ma et al, APL (2014); [3] Y. Ma et al, Sci. Reports 6, 30491(2016) [4] K. Huang et al, APL (2014) [5] K. Huang et al, Sci. Reports 6, 27633(2016)
55
Trapping electrons in a standing wave for ion
acceleration and radiation generation
Arkady Gonoskov*
Department of Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950, Russia
Lobachevsky State University of Nizhni Novgorod, Nizhny Novgorod 603950, Russia *[email protected]
High-intensity lasers provide pulses with remarkable localization of electromagnetic energy, giving a base for
a rapid particle acceleration and radiation generation. In many scenarios, spatial and temporal synchronization of
particles with accelerating fields plays a crucial role for efficient energy conversion. For example, especially high
efficiency is achieved for acceleration of electrons, which due to their small mass can quickly start to follow the
pulse propagation, gaining energy continuously over a large distance via the mechanism of LWFA.
Due to their much higher mass, it is more difficult to synchronize the motion of ions with accelerating fields.
Since the accelerating fields are typically provided by the electrons, their localization and relocation can provide
a pathway for efficient acceleration of ions. One can achieve this by trapping electrons in the moving node of a
standing wave, produced by reflection of a chirped laser pulse from a solid surface [1]. This concept, called
Chirped-Standing-Wave Acceleration (CSWA), has opened a new approach for a uniquely controllable
acceleration of ions.
Another interesting example of the benefit of trapped electron dynamics in a standing wave concerns the
production of collimated gamma ray beams from electron-positron cascades. These are expected to be triggered
at the next generation of multi-PW laser facilities. Producing a large number of electrons and positrons that can
emit high energy photons is favoured by tightly focusing and colliding several laser pulses. In this case, the
electrons and positrons cannot follow radiation as in LWFA and are expected to be expelled by the laser radiation
out of the focal spot. However, the recently discovered phenomenon of anomalous radiative trapping (ART) [2]
provides an opportunity to trigger counterintuitive dynamics in the vicinity of the electric field antinodes. These
dynamics are especially good for gaining and releasing energy in the form of high-energy photons that are well-
collimated along the electric field polarization [3].
In this way, trapping and controlling electrons by a standing wave can be seen as a basic approach for
controlling the process of laser-plasma interaction. In my talk I will cover some general aspects of particle trapping
in a strong standing wave, and address the latest progress on the above-mentioned concepts.
References [1] F. Mackenroth, A. Gonoskov, M. Marklund Phys. Rev. Lett., 117 (10), 104801 (2016). [2] A. Gonoskov et al. Phys. Rev. Lett., 113, 014801, (2014). [3] A. Gonoskov et al. arXiv:1610.06404 (2016).
56
Recent progress of laser plasma
physics and advanced accelerator research at Tsingh
ua University
Wei Lu*
Tsinghua University, Beijing 100084 China *[email protected]
The recent progress of L2PA (Laboratory of Laser Plasma Physics and Advanced Accelerator Technology) at
Tsinghua University will be presented. On experimental results, several experiments will be reported: (1) 10-
40MeV high quality electron beams can be generated through controlled self-injection using a 5TW laser, and
under proper conditions low relative energy spread (<1%) and very low absolute energy spread ( 0.18MeV) can
be achieved. (2) Using a 50TW laser at the joint experimental platform of NCU, 250-435MeV high quality
electron beams with low energy spread (2-5%) have been obtained; (3) using 70MeV electron beams generated
by a LWFA as a probe, we have successfully demonstrated the electron snapshot of wakefield structure, and
measured wakefield dynamics on a density ramp[1]; (4) Using a plasma dechirper to reduce the energy spread of
electron beams has been demonstrated.
On theory and simulation, several ideas on how to obtain high quality electron beams with extremely high
brightness through wakefield acceleration will be discussed[2]. Furthermore, theoretical model of the phase space
dynamics of ionization injection [3] and phase space matching for staging accelerator components using
longitudinally tailored plasma profiles will also be discussed[4].
References
[1] C. J. Zhang, et al., submitted to PRL
[2] F. Li et al., Phys. Rev. Lett. 111, 015003 (2013)
[3] X. L. Xu et al., Phys. Rev. Lett. 112, 035003 (2014)
[4] X. L. Xu et al., Phys. Rev. Lett. 116, 124801 (2016)
57
Recent progress in simulation and theory towards
using nonlinear plasma wakefields to drive a
compact X-FEL
Xinlu Xu*, Wei Lu, Joshi Chan and Warren B. Mori
University of California, Los Angeles, California 90095, USA SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
Department of Engineering Physics, Tsinghua University, Beijing 100084, China *[email protected]
X-ray free electron lasers (X-FELs) driven by kilometer-long radio-frequency based accelerators have already
proven to be transformative tools for modern science. Using plasma wakefields accelerators to drive compact X-
FELs can much reduce the cost and shrink the size, making it possible to place one at universities. However there
are many challenges needed to be overcome before plasma wakefields can generate electron beams with the
required beam quality (brightnesses and low energy spreads) inside the plasma and before these beams can be
transported from the plasma to the undulator without beam quality degradation. In this talk, we will present our
recent progress from PIC simulations and theory on this topic, including concepts for producing beams with
unprecedented normalized brightnesses using density down ramp injection in the nonlinear blowout regime,
matching the beam out of the plasma using longitudinally tailored plasma profiles, and start-to-end simulations
of such plasma wakefied accelerators driven X-FELs.
58
Laser Wakefield Accelerator Based Photon Sources
Alec Thomas1*
1Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109, USA *[email protected]
Recent progress in laser wakefield acceleration has led to the emergence of a new generation of electron and
X-ray sources that may have considerable benefits for ultrafast science. Laser wakefield acceleration provides
radiation pulses that have femtosecond duration and intrinsic synchronisation with the laser source, allowing for
pump-probe measurements with unprecedented temporal resolution. These pulses can be used to study ultrafast
dynamical phenomena in plasma and dense material, such as transient magnetic fields, rapidly evolving plasma
dynamics and crystal lattice oscillations. I will review our recent experiments in laser wakefield acceleration and
energetic photon generation using the laser systems at the University of Michigan and STFC Rutherford Appleton
Laboratory and their use for capturing the dynamics of laser-pumped samples. Single-shot, spectrally resolved
absorption measurements in laser pumped foils can be made on ultrafast timescales using this broadband photon
source. X-ray and electron diffraction using beams from laser-plasma sources capture structural dynamics
in crystalline samples. I will also discuss the technological needs for and potential impact of such revolutionary
compact radiation sources for ultrafast science in the future.
59
Emittance measurements and transport for the
BELLA center free electron laser
S. K. Barber1*, J. van Tilborg1, C. B. Schroeder1, F. Isono1,2, R. Lehe1, H.-E Tsai1, K. K. Swanson1,2, S. Steinke1, K. Nakamura1, C. G. R. Geddes1, C. Benedetti1, E. Esarey1, and W.P. Leemans1,2
1Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA 2Department of Physics, University of California, Berkeley, California 94720, USA
G. Andonian, N. Majernik, R. Patil, J. B. Rosenzweig Department of Physics, University of California, Los Angeles, California 90095, USA
The success of many laser plasma accelerator (LPA) based applications, such as a compact x-ray free electron
laser (FEL), relies on the ability to produce electron beams with excellent 6D brightness, where brightness is
defined as the ratio of charge to the product of the three normalized emittances. As such, parametric studies of the
emittance of LPA generated electron beams are essential. Profiting from a stable and tunable LPA setup, combined
with a carefully designed single-shot emittance diagnostic, we present a direct comparison of charge dependent
emittance measurements of electron beams generated by two different injection mechanisms: ionization injection
and shock induced density down-ramp injection. Notably, the measurements reveal that ionization injection results
in significantly higher emittance. With the down-ramp injection configuration, emittances less than 1 micron at
spectral charge densities up to ~2 pC/MeV were measured. These measurements are discussed in the greater
context of the BELLA Center FEL project which aims to demonstrate FEL amplification using the 4 meter VISA
undulator. Various aspects of this project, including transport design, FEL simulation and the development of a
novel electromagnetic chicane for longitudinal bunch decompression are discussed in detail.
60
Laser driven proton acceleration with solid and gas
targets
Baifei Shen1,2, Wenpeng Wang2, Jiancai Xu2, Hui Zhang2, Shuhua Zhai2, Ruxin Li2, and Zhizhan Xu2
1Department of Physics, Shanghai Normal University, Shanghai 200234, China. 2State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of
Sciences, P. O. Box 800-211, Shanghai 201800, China.
Experiments for laser driven proton acceleration were carried out by using the femtosecond petawatt laser
system at Shanghai Institute of Optics and Fine Mechanics (SIOM), Chinese Academy of Sciences (CAS). With
an overdense plasma produced by the laser prepulse ionizing an initially ultrathin plastic foil, proton beams with
narrow spectral peaks at energies up to 9 MeV, and with fluxes of as high as ~3 × 1012 protons/MeV/sr which is
increased by two orders of magnitude compared with previous experimental results, were observed. Two-
dimensional particle-in-cell simulations reveal that collisionless shocks are efficiently launched by circularly
polarized lasers in exploded plasmas, resulting in a narrow energy spectrum. [1] A highly-collimated argon ion
beam with narrow energy spread is produced by irradiating a 45-fs fully-relativistic laser pulse onto an argon
cluster target. The argon ions get pre-accelerated from Coulomb explosion and then the laser-driven intense
plasma wakefield has a strong modulation on the ion beam in a way that the low energy part is cut off. [2] The
optimum and controllable two-stage proton acceleration was realized for the first time by a novel double beam
image (DBI) technique in experiment. Two laser pulses are successfully tuned on two separated foils with both
spatial collineation and time synchronizing, resulting in spectrum tailoring and an energy increase at the same
time. [3] A strong electromagnetic pulse (EMP) is generated on a copper mesh which is irradiated by a laser pulse
and propagates on it, forming an EMP mesh. After flying through the copper mesh, a laser driven proton beam is
divided into several beamlets and each beamlet was separately focused due to the electric force of the EMP. The
area density of proton beamlet focused by the EMP is 25 times as many as the initial density of the proton beam.
[4]
References [1] Hui Zhang, Baifei Shen et al., to be submittd. [2] Jiancai Xu, Baifei Shen et al., submitted. [3] Wenpeng Wang, Baifei Shen et al., submitted. [4] Shuhua Zhai, Baifei et al., to be submitted.
61
Stable, polarized betatron radiation and
applications
Andreas S. Döpp1,2*, Benoît Mahieu1, Agustin Lifschitz1, Antoine Doche1, Cédric Thaury1, Sébastien Corde1, Julien Gautier1, Emilien Guillaume1, Gabriele Grittani3, Olle Lundh4, Martin Hansson4,
Michaela Kozlova3, Fabien Dorchies5, Noémie Jourdain6, Ludovic Lecherbourg6, Jean Philippe Goddet1, Pascal Rousseau1, Amar Tafzi1, Victor Malka1, Antoine Rousse1 and Kim Ta Phuoc1
1 Laboratoire d’Optique Appliquée, ENSTA, CNRS UMR7639, Ecole Polytechnique, Palaiseau, France.
2 Ludwig-Maximilians-Universität München, Garching, Germany 3 ELI Beamlines Project, Institute of Physics of the ASCR, Prague 8, Czech Republic.
4 Department of Physics, Lund University, Lund, Sweden. 5 Ctr. Lasers Intenses et Applications, Univ. Bordeaux 1 (France)
6 Commissariat à l'Énergie Atomique (France) 7 Department of Physics and Complex Systems, Weizmann Institute of Science, Rehovot, Israel
Betatron oscillations in laser-plasma accelerators lead to the emission of synchrotron-like X-rays with
femtosecond duration. While the sources’ properties are potentially interesting for many applications, the
important shot-to-shot fluctuations of flux, beam-profile and energy have hindered its success.
In this talk, we present recent results on the reliable production of betatron radiation with tunable polarization.
Using ionization-induced injection in a gas mixture, the orbits of the relativistic electrons emitting the radiation
are reproducible and controlled. We observe that both the signal and beam profile fluctuations are significantly
reduced and that the beam pointing varies by less than a tenth of the beam divergence. The polarization ratio
reaches 80 percent, and the polarization axis can be easily rotated. Using the source, we present first applications
in ultrafast X-ray absorption spectroscopy and give an outlook on other potential applications.
References [1] A. Döpp et al. Stable femtosecond X-rays with tunable polarization from a laser-driven accelerator. Light: Science & Applications accepted article preview 12 May 2017; doi:10.1038/lsa.2017.86
62
Towards all-optical ion accelerator by an innovative
target scheme
S. Kar*
School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, UK *[email protected]
In the context of developing compact, high current ion accelerators, the study of intense laser driven
acceleration mechanisms and optimisation of the ion beams produced, have been, over the past decade, very active
areas of research. For instance, demonstrating capability of a controlled, all-optical acceleration of protons and
other low-Z ion species in the 60-300 MeV/nucleon range would be of significant interest for therapy of deep-
seated cancer. Emerging laser-driven ion acceleration mechanisms, including the Radiation Pressure Acceleration
approaches, are highly promising for this purpose and currently pursued internationally. A novel scheme of guided
post-acceleration of the laser driven ion beams was recently developed [1], which brings the all-optical scheme
one step closer to the realization of compact beam lines.
High power lasers are capable of generating giant electromagnetic (EM) pulses due to prompt escape of hot
electrons from the interaction region. The large electric field associated to the EM pulses can be harnessed in a
travelling-wave particle accelerator arrangement, by directing the ultra-short EM pulse along a helical path
surrounding a laser-accelerated ion beam. The radial and longitudinal components of the associated electric field
within the helix leads to simultaneous beam shaping and re-acceleration of a selected portion of the proton beam.
In a proof-of-principle experiment on a 200 TW university-scale laser, post-acceleration of ~108 protons by ~5
MeV was demonstrated with dynamic beam collimation and energy selection. The acceleration gradient in this
case was ~0.5 GeV/m, which is already beyond what can be sustained by conventional accelerator technologies.
Employing this technique recently at the Vulcan Petawatt laser and Titan laser, LLNL, USA, produced a narrow
band, pencil beam of ~ 45 MeV, where preliminary analysis indicates fast scaling of the post-acceleration gradient
with laser power. Furthermore, there is significant scope for optimising the acceleration by using extended helical
coils of variable pitch and diameter. While this technique may provide the platform for a practical ‘table-top’
accelerator by staging multiple coils, achieving this objective requires a coordinated effort involving development
of targetry, understanding and controlling the physical processes of the relevant interaction regimes, and
developing innovative solutions to a number of technical bottlenecks.
References [1] S. Kar et. al., Nature communication, 7, 10792 (2016)
63
(a)
Controlling radiation losses by quantum quenching
C. N. Harvey, A. Gonoskov, A. Ilderton†, and M. Marklund*
Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden †Currently at Centre for Mathematical Sciences, Plymouth University, PL4 8AA, UK
*[email protected] Continual advances in achievable laser power has spurred renewed interest in using intense light to
study fundamental predictions of classical and quantum electrodynamics (QED) [1–5]. One cornerstone of such experiments is the collision of laser beams with particle bunches [6, 7]. Particle motion in intense fields is inherently non-linear, in particular due to radiation reaction (RR) which is the impact of energy loss on particle motion. RR can reduce collision energies [8], hinder particle acceleration schemes [2, 9, 10], and is seemingly unavoidable. Much work has gone into demonstrating that RR, long thought negligible, must now be accounted for in order to accurately model state-of-the-art high intensity laser- matter interactions [2, 11, 12]. Here, we will show on a different facet of the quantum nature of radiation reaction. Using analytical results, as well as both single particle and particle-in-cell simulations, we demonstrate that one can control, and effectively turn off, RR by tuning the laser pulse length. We will also present a realisable experimental setup (see Fig. 1), requiring only modest parameters, with which to observe the effect and so demonstrate a possibility to control quantum processes in intense light-matter interactions [13].
x z y
laser pulse
𝐵𝐵source
lanex screen
magnet
slit
focusing mirror
laser pulse
particle beam source
Figure 1. Proposed experimental setup for testing quantum quenching.
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References [1] M. Marklund and P. K. Shukla, Rev. Mod. Phys. 78, 591 (2006). [2] A. Di Piazza, C. Muller, K. Z. Hatsagortsyan, and C. H. Keitel, Rev. Mod. Phys. 84, 1177 (2012). [3] E.Lundström,G.Brodin,J.Lundin,M.Marklund,R.Bingham, J. Collier, J. T. Mendonca, and P. Norreys, Phys. Rev. Lett. 96, 083602 (2006). [4] T. Heinzl, B. Liesfeld, K.-U. Amthor, H. Schwoerer, R. Sauerbrey, and A. Wipf, Opt. Commun. 267, 318 (2006). [5] B. King, A. Di Piazza, and C. H. Keitel, Nature Photon. 4, 92 (2010). [6] S.-y. Chen, A. Maksimchuk, and D. Umstadter, Nature 396, 653 (1998). [7] C. Bula et al. (E144), Phys. Rev. Lett. 76, 3116 (1996). [8] A. M. Fedotov, N. V. Elkina, E. G. Gelfer, N. B. Narozhny, and H. Ruhl, Phys. Rev. A 90, 053847 (2014). [9] S. V. Bulanov, T. Z. Esirkepov, J. Koga, and T. Tajima, Plasma Physics Reports 30, 196 (2004). [10] V. Malka, J. Faure, Y. A. Gauduel, E. Lefebvre, A. Rousse, and K. T. Phuoc, Nature Physics 4, 447 (2008). [11] D. A. Burton and A. Noble, Contemp. Phys. 55, 110 (2014), arXiv:1409.7707 [physics.plasm-ph]. [12] A. Gonoskov, S. Bastrakov, E. Efimenko, A. Ilderton, M. Marklund, I. Meyerov, A. Muraviev, A. Sergeev, I. Surmin, and E. Wallin, Phys. Rev. E 92, 023305 (2015). [13] C. N. Harvey, A. Gonoskov, A. Ilderton, and M. Marklund, Phys. Rev. Lett. 118, 105004 (2017).
65
Scaling laws for positron production in laser—
electron-beam collisions
T. G. Blackburn1*, A. I. Ilderton2, C. D. Murphy3 and M. Marklund1
1Department of Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden 2Centre for Mathematical Sciences, University of Plymouth, PL4 8AA, UK
3York Plasma Institute, Department of Physics, University of York, York, YO10 5DD, UK *[email protected]
Showers of gamma rays and positrons are produced when a multi-GeV electron beam collides with a super-
intense laser pulse [1]. All-optical realisation of this geometry, where the electron beam is generated by laser-
wakefield acceleration [2], is currently attracting much experimental interest as a probe of radiation reaction and
QED effects. These interactions may be modelled theoretically in the framework of strong-field QED [3] or
numerically by large-scale PIC simulation [4]. To complement these, we present analytical scaling laws for the
electron beam energy loss, gamma ray spectrum, and the positron yield and energy that are valid in the radiation-
reaction—dominated regime. These indicate that by employing the collision of a 2 GeV electron beam with a laser
pulse of intensity 5×1021 W/cm2, it is possible to produce 10,000 positrons in a single shot at currently available
laser facilities.
References [1] D. L. Burke et al., Phys. Rev. Lett. 79, 1626 (1997). [2] G. Sarri et al., Phys. Rev. Lett. 113, 224801 (2014). [3] A. Di Piazza, Phys Rev. Lett. 117, 213201 (2016). [4] M. Lobet, X. Davoine, E. d’Humieres and L. Gremillet, Phys. Rev. Accel. Beams 20, 043401 (2017).
66
µν
Radiation reaction damping and ultra-intense ga
mma-ray flash generation in QED regime
Z. Gong*, R. H. Hu, W. J. Ma, C. Lin, H. Y. Lu and X. Q. Yan*
State Key Laboratory of Nuclear Physics and Technology, and Key Laboratory of HEDP of the Ministry of Education, CAPT, Peking University, Beijing, China, 100871
*[email protected] *[email protected]
An accelerated charged particle must be accompanied with radiation and corresponding radiation
damping. The prospective tens petawatt-class short pulse laser may bring us into the radiation dominant
regime [1] and quantum electrodynamics (QED) regime [2]. The entropy reduction and cooling in phase
space are exhibited when radiation friction term being added to Lorentz equation. The electric nodes in
circularly polarized counter- propagating laser field behave spiral attractive property and the ratio of
electron accumulation nearby phase space can be obtained through eigen equation and eigenvalue
[3]. However, when quantum parameter
χe =| F pν | / Es
mec approaches unity, the classical continuous radiation description cannot explain the discrete
photon emission, pair plasma generation and quantum straggling effect. In multi strong pulse colliding
configuration [4], the seeded electrons can be confined and accelerated efficiently to produce gamma-
ray explosion and pair cascades, which provides potential application in laboratory astrophysics and e+e-
collider.
References [1] S. Bulanov, T. Z. Esirkepov, M. Kando, J. Koga, K. Kondo, and G. Korn, Plasma Physics Reports 41, 1 (2015). [2] A. Di Piazza, C. Muller, K. Hatsagortsyan, and C. Keitel, Reviews of Modern Physics 84, 1177 (2012). [3] Z. Gong, et al. "Radiation reaction induced spiral attractors in ultra-intense colliding laser beams." Matter and Radiation at Extremes 1.6 (2016): 308-315. [4] Z. Gong, et al. "High-efficiency γ-ray flash generation via multiple-laser scattering in ponderomotive potential well." Physical Review E 95.1 (2017): 013210.
67
Quantum vs. classical radiation reaction
Marija Vranic1* , Thomas Grismayer1, Ricardo A. Fonseca1,2 and Luis O. Silva1
1GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, 1049-001 Lisbon, Portugal
2DCTI/ISCTE—Instituto Universitário de Lisboa, 1649-026 Lisboa, Portugal * [email protected]
New generation of laser facilities will provide intense laser fields that will alow us to explore the radiation
reaction dominated regime. It will be possible to measure signatures of both, quantum and classical radiation
reaction in the laboratory. In our particle-in-cell code OSIRIS, we have incorporated continuous classical radiation
reaction through Landau & Lifshitz equation of motion, and high-energy photon emission via nonlinear Compton
scattering. One can use this tool to identify quantum radiation reaction signatures for future all-optical experiments
where GeV electrons obtained through Laser Wakefield acceleration collide with intense laser pulses. The most
pronounced QED signatures are reflected on the electron beam energy distribution function: classical radiation
reaction always tends to decrease the energy spread [1], but the inherent stochasticity of quantum emission tends
to increase it. We have identified an upper limit to such an increase. Based on this conclusion, we will present a
theoretical estimate for the final width of the electron energy distribution function after the interaction with laser
pulses of different durations, supported by QED PIC simulations [2]. We will also discuss how the increase of the
enregy spread is related with the beam divergence. QED radiation reaction is illustrated in Fig. 1.
Figure 12. QED radiation reaction and photon detection.
References [1] M. Vranic, J. L Martins et. al, Phys. Rev. Lett. 113, 134801 (2014). [2] M. Vranic, T. Grismayer et. al, New J. Phys, 18, 073035 (2016).
68
New Generating Schemes of Tunable Narrowband
Terahertz Radiation in Plasmas by Femtosecond
Laser Pulses
Vladimir Annenkov*, Igor Timofeev, Evgeniia Volchok
Budker Institute of Nuclear Physics, Siberian Branch of Russian Academy of Sciences, 630090, Novosibirsk, Russia Novosibirsk State University, 630090 Novosibirsk, Russia
In recent decades, the creation of powerful and tunable sources of terahertz radiation has become the field of
active research in both laser and accelerator communities. The most significant progress has been achieved in
generating high-field (up to 100 MV/cm) wide-band (single-cycle) THz pulses. The creation of high-power
sources of tunable THz radiation with a narrow spectral line and high values of electric field is also highly
demanded today, since it opens the way to different new problems in physics, chemistry, biomedicine and
spectroscopy.
In this work, via the analytical theory and particle-in-cell simulations, we discuss several new compact
schemes for the generation of tunable narrow-band THz radiation in a plasma by two counterpropagating
femtosecond laser pulses. Our proposal is based on the following effect: superposition of laser-induced wakefields
traveling in opposite directions along the coordinate x generates the nonlinear electric current which oscillates
with the doubled plasma frequency and does not depend on the longitudinal coordinate. This current density does
not vanish and can produce transversely propagating EM radiation if the transverse structure of the first plasma
wave differs from the similar structure of the second wave (E1(y) ≠ E2(y)). In experiments, this effect can be
implemented either by using counterpropagating laser pulses focused into a gas (in a jet either in a glass tube) or
by reflecting a single laser pulse from a plasma mirror.
The first theoretical estimates, in good agreement with simulation results, show that the joule-scale laser beams
with the wavelength 800 nm are able to generate gigawatt terahertz pulses (20-30 THz) with the energy 1 mJ,
electric field >10 MV/cm and the narrow linewidth (~1%). If the role of the driver is played by the 100 TW CO2
laser, the power and energy of generated narrow-band THz pulses, according to this theory, can reach the level of
1 GW and 20 mJ even in the low-frequency range 1-5 THz.
Produced radiation is concentrated near the doubled plasma frequency and can freely escape from the plasma.
Moreover, by changing the plasma density n0, one can easily vary the radiation frequency in a wide range. The
successful implementation of such schemes will allow to exceed the maximal energy of THz pulses achieved in
the most powerful free electron laser by more than tenfold.
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Impact of injection-gas concentration of the quality
of electron beam generated by laser plasma
acceleration
Mohammad Mirzaie*, Guobo Zhang and Nasr A.M. Hafz
Key Laboratory for Laser Plasmas (MOE), School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
Since the time laser wakefield acceleration (LWFA) was proposed [1], it had rapid progress speeding out
with the availability of commercial tabletop ultra-fast high power laser systems [2]. With development of such
laser systems, higher electric field where achieved and gave possibility of electron acceleration from the plasma
itself (instead of external injection) to reach higher energy. Later, generation of high-quality electron beam in
terms of energy, energy spread, charge, divergence angle and bunch duration became very important. To
improve the high quality electron beam parameters, several injection mechanisms were proposed and
demonstrated experimentally. Among those injection mechanisms, self-truncated ionization injection (STII), a
modified version of ionization injection mechanism, have shown promising results for generating high energy
and low energy spread electron beam [3,4]. In this mechanism high intensity laser pulse with unmatched large
laser spot size interacts with a gas target, mixture of high-Z gas (injection gas) and low-Z gas (host gas).
In this work, using intense (30 TW), ultrashort (30 fs) laser pulses we report the impact of the injection gas
concentration on the quality of electron beams generated by a laser-driven wakefield acceleration employing the
ionization injection. The host gas was helium while the injection gas was nitrogen. In the experiment depending
on the amount of nitrogen added to the helium host gas, we could distinguish a clear trend on the quality of the
generated electron beams in terms of energy, energy-spread, divergence angle and beam charge. The results have
shown that the lower the nitrogen concentration the higher the generated electron beam quality. A 2D PIC
simulation also was performed to support the experiment. The simulation result was in good agreement with the
experimental results.
References [1] T. Tajima and J.M. Dawson, Phys. Rev. Lett. 43, 267 (1979). [2] G. A. Mourou, T. Tajima and S.V. Bulanov Rev. Mod. Phys. 78, 309–371 (2006). [3] M. Zeng, M. Chen, Z. M. Sheng, W. B. Mori and J. Zhang, Phys. Plasmas 21, 030701(2014). [4] M. Mirzaie et al. Sci. Rep. 5, 14659 (2015).
70
Femtosecond probing of plasma wakefields and
observation of a plasma wake echo using a
relativistic electron bunch
Chaojie Zhang1,*, Chan Joshi1, Warren B. Mori1,2, Jyhpyng Wang3,4,5, and Wei Lu6
1Department of Electrical Engineering, UCLA, CA 90095, USA 2Department of Physics and Astronomy, UCLA, CA 90095, USA
3Department of Physics, National Central University, Jhong-Li 32001, Taiwan 4Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan
5Department of Physics, National Taiwan University, Taipei 10617, Taiwan 6Department of Engineering Physics, Tsinghua University, Beijing 100084, China
The instantaneous longitudinal and transverse field structures of a microscopic, highly transient, laser-excited
relativistic plasma wake is captured with femtosecond resolution. This is done by using the high-energy ultrashort
electron bunch generated from a laser wakefield accelerator as a probe as firstly proposed in [1]. Furthermore, we
have probed the structure of wakefields in a density gradient for the first time. By recording the temporal evolution
of the plasma wake wavelength in a density upramp, an echo, i.e., the recurrence of the plasma wake is observed.
It is found that after the laser driver has passed, the local wake wavelength first increases with time until it
eventually tends to infinity, then it begins to shorten and the phase velocity of the wake reverses its direction. In
a density downramp, the wake wavelength monotonically decreases as a function of time until it can eventually
be damped by wave-particle interactions [2]. Both the existence of wake echo in a density upramp and its absence
in a density downramp are theoretically explained and confirmed in particle-in-cell simulations.
References [1] C. Zhang et al., Sci Reports 6, 29485 (2016). [2] J. Dawson, Phys Fluids 4, 869 (1961).
71
High-energy bremsstrahlung radiation from laser-
plasma accelerators from solid high-Z targets to
explore internal hot electron beam dynamics.
C. D. Armstrong1,2*, C.M. Brenner2, D.R. Rusby1,2, P. McKenna1, and D. Neely2
1University of Strathclyde, Glasgow, UK 2Central Laser Facility, Rutherford Appleton Laboratory, UK
As a high-intensity laser interacts with a solid target, a plasma is formed on the front surface, and electrons
are accelerated into the target with a broad Maxwellian (or Maxwell-Jutner) distribution of energies. These
‘hot’ electrons interact with the atomic fields within the target and generate high-energy bremsstrahlung
emission throughout the target as well as establishing charge-separation sheath fields on the target surfaces,
which then accelerate ion beams. A full understanding of this aspect of extreme light-matter interaction physics
is crucial to the development and optimisation of these laser-driven sources for use in clinical and industrial
applications [1], such as radiography and neutron probing. Presented here is results and discussion of
characterization of the escaping bremsstrahlung temperature, >150keV spatial profile and its relevance to the
study of hot electron transport for radiation generation.
Unlike charged particle emission, the x-ray radiation can escape the target unperturbed by the sheath generated
at the rear surface and therefore sampling this emission gives us a direct probe from which we gain information
of the internal dynamics of the hot electron current and transport. The x-ray spectrum is dependent on the internal
electron temperature and the radiation transport through the target material. By characterizing the x-ray emission
we can then deconvolve the shot-by-shot internal electron temperature using radiation transport simulation codes
[2] and avoid inferring temperatures from scaling laws. While the spectral information can tell us about the energy
contained within the internal current, we can use the spatial profile of the x-ray emission to discern information
about the global electron beam divergence [3]. For ultra-relativistic electrons (>8MeV) the emission angle of x-
ray radiation collapses to fractions of a degree and so sampling this energy region allows us to profile the angular
distribution of the high-energy tail of the electron beam.
We discuss a combination of results from experiments on the Vulcan Petawatt Laser system at the STFC
Central Laser Facility, and simulation work using the Monte-Carlo code GEANT4. The results are discussed in
line with imaging large scale industrial objects, exploring the trade-offs between changes in the emission to
optimize the imaging capability. With that in mind, we discuss results from conventional x-ray converters, such
as thick tantalum, and thin foil targets typically excluded due to low yield.
References [1] C M Brenner et al 2016 Laser-driven x-ray and neutron source development for industrial applications of plasma accelerators Plasma Phys. Control. Fusion 58 014039; doi:10.1088/0741-3335/58/1/014039
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[2] D.R. Rusby et al Pulsed x-ray imaging of high-density objects using a ten picosecond high-intensity laser driver Proc. SPIE 9992 (October 25, 2016); doi:10.1117/12.2241776. [3] Green, J. S., et al. "Effect of laser intensity on fast-electron-beam divergence in solid-density plasmas." Physical review letters 100.1(2008): 015003.