j zhang institute of physics, cas, beijing 100080 - …wls.iphy.ac.cn/chinese/1219/1/fmgkx/2.pdf ·...
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Plasma-based x-ray lasers
J ZhangInstitute of Physics, CAS, Beijing 100080
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Visible Light Lasers vs. X-Ray Lasers
1. Laser medium: atoms and molecules 2. Wavelength: visible range3. High-Reflecting/Low Trans- mirror: exist4. Cavity is possible: many passes=>small gain required5. Coherence properties: high
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Visible Light Lasers vs. X-Ray Lasers
Still stimulated emissionUtilizing the inverse populations between energy levels of ions.• Wavelength of soft XRL: several~tens nanometers• Laser medium: highly ionized plasmas=>energy consuming• (Wavelength of x-ray laser) ~ (drive energy)-4
• High-Reflecting mirror is difficult to achieve• No Cavity: single pass, ASE =>huge gain required• Strict requirement on uniformity along the plasma
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Necessary Conditions for X-Ray Lasers
1. Specific ions utilized:high photon energy, relatively high abundance, Ne-or Ni-like ions used.
2. Electrons of high density and high temperature: ionization, excitation3. Spatial and temporal overlap of electron density distribution,
temperature distribution, Ion density distribution, pumping photons4. Temporal overlap requirement vs. ion energy level life-span:
traveling-wave pumping technique.5. No HR mirrors for cavity, single-pass amplification: huge gain
requirement, =>high electron density with smooth spatial distributionprofile for necessary long propagation.
6. Coherence properties: multi-modes, long propagation in gain medium is probably a method to achieve high spatial coherence.
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Laser transition
4p
4d
3d10 Ni-like ions
Strong radiationdecay
3d
Laser transition
Monopole collisionalexcitaion
3s
3p
2p6 Ne-like ions
Strong radiationdecay
2p
Ne-like x-ray lasers Ni-like x-ray lasers
Specific ions: => Short wavelength (30-250eV); Qusai-steady state configuration, population inversion between 3p(4d) - 3s (4p)
Necessary Conditions for X-Ray Lasers
1s22s22p6 1s22s22p63s23p63d84s2
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High electron density and temperature: => for abundant specific ions production and population inversion formation, Ti
Necessary Conditions for X-Ray Lasers
22Ti’s Ionization E(eV) of electrons
10 2.16240E+02
11 2.63909E+02
2.92014E+02
7.89623E+02
8.69645E+02
9.52577E+02
1.03842E+03
12
13 (10th)
14
15
16
Ti, Upper-lower level Energy (eV)
2p63p(J=0): 6.21581E+02 eV
2p63s(J=1): 5.19976E+02 eV
47Ag’s Ionization E(eV) of electrons
3.80590E+02
4.10540E+02
4.45870E+02
5.15370E+02
9.00000E+02
9.54480E+02
1.00820E+03
1.06630E+03
19 (28th)
5.19976E+02 eV(J=1):
6.21581E+02 eV(J=0):
Ag, Upper-lower level Energy (eV)
0 500 1000 1500 20000.0
0.5
1.0
1.5
2.0
2.5
<δv>
(x10
-10 cm
3 /s)
Electron Temperature (eV)
Electron collision excitation rate
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Variables’ Spatial and temporal overlap : => for optimum x-ray laser beam output; Te, De, Distribution of specific ions
Necessary Conditions for X-Ray Lasers
Electron density
Ne-like Tiabundance
Overlap of electron density and Ne-like Ti ion distribution with different laser configurations
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Single pass amplification : => huge gain required; smooth electron density profile necessary; long gain medium necessary
Necessary Conditions for X-Ray Lasers
Gain Region
De
x
ce NNn −= 1
220 4/ emNc πω=
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Two Main Goals for the Development of X-Ray Lasers
1. Lasing action at a wavelength as short as possible
Invention of maser at microwave in 1954
Invention of laser at infra red and visible light range in 1960
Theoretical ideas about laser at X-rays in 1960
Experimental observation of X-ray lasers in 1984
First saturated operation of X-ray lasers at 19.6 nm in 1992
First saturated operation at a wavelength shorter than 10 nm in 1996
Saturated x-ray laser at 5.8 nm in 1997, approaching the water window
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Two Main Goals for the Development of X-Ray Lasers
2. X-ray lasers driven by smaller drivers with higher repetition rate
OFI/Recombination Pumping X-ray Lasers in 1993
Capillary Discharge X-ray lasers in 1994
OFI/Collisional Pumping x-ray laser in 1995
Table-top x-ray laser, more efficiencySaturated x-ray lasers produced using several J
Longitudinal pumping and grazing incidence pumpingSaturated operation of x-ray laser at 18.9 nm using 150mJ at 10 Hz
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Development of X-Ray Lasers------first observation
1. Theory: Transition between 2p53p(J=0) 2p53s(J=1) dominates in Ne-like ionsExcitation rates from 2p6 to 2p53p is larger than that from 2p6 to 2p53s;Transition to 2p53p(J=0) through direct monopole excitationTransitions to other levels primarily fed by cascades and recombinations
Dominating lines: Which transition dominates x-ray spectra
1. 12. Experiments: Transition between 2p53p(J=2) 2p53s(J=1) dominates in Ne-like ions
Matthews’s first observation of xrlamplification
Phys. Rev. Lett. 54, 110 (1985)
Amplified transitions:(2p3/23p3/2)J=2->(2p3/23s)J=1(2p1/23p3/2)J=2->(2p1/23s)J=1
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Development of X-Ray Lasers------exploding foil targets
Dominating lines: Lack of predicted lines is due to x-ray’s refraction? Modulating density: Exploding foil targets minimizing the refraction problem.
Rosen’s exploding foil target technique,Observing amplification of transitions (J=2->1)No predicted (J=0->1) dominating.
Problem of dominating lines is closely related to the physical processes in the plasma medium.
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Development of X-Ray Lasers------prepulse technique
Electron Density: Prepulse technique produces smooth electron densityat high density region where J=0->1 lasing takes place
Ne-like Se
Nilson’s experiments with prepulseNilson’s experiments with multi-pulses
Pre-pulse advantages: 1. Produce uniform plasma column with proper electron density, allowing long propagation and
sufficient amplification for saturated output; 2. Preformed plasmas cool down so that driving laser can be absorbed directly in the gain region;
Electron density
Without Prepulse
With prepulse
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Development of X-Ray Lasers------xrl saturation output
Saturation output: Saturation output indicates the stimulated emission extracts the maximum power possible for an excited plasmas; Necessary for applications; All utilize prepulse technique.
Neon-like ions:Transition J=2->1 Transition J=0->1
Ge 23.6nm Ti 32.6nm
Ge 23.2nm Fe 25.5nm
Se 20.6nm Zn 21.2nm
Y 15.5nm Ge 19.6nm
5.86nmDy
7.3nmSm
12.0nmSn
13.2nmCd
14.0nmAg
14.7nmPd
18.9nmMo
20.3nmNb
Nickle-like ion systems:
Driving laser configuration and target configuration are essential for saturation output of xrl.
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Development of X-Ray Lasers------Refraction compensation
Double targets: for compensation of the x-ray beam refraction
Double 75 ps pulse separated by 2.2 ns.Focused intensity on target 1~4x10 13 W/cm -2.
Demonstration of Saturation in a Ni-like Ag X-Ray laser at 14 nm; Zhang et al, PRL 78, 3856 (1997)
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Development of X-Ray Lasers------Approaching water window
Water window wavelength: for coherent biological x-ray imaging
Saturated Amplification in Ni-like Sm at 7 nmZhang et al, Science 276, 1097 (1997)
0
0.2
0.4
0.6
0.8
1
20 40 60 80 100 120 140 160 180 200 220 240
ProteinWater
Tran
smis
sion
Wavelength (?
AgInSn
Sm
TaYb
Gd
Dy
W
Water Window
Y GeLLNL(94)RAL(97)
RAL(97)
RAL(96)
Planned at RAL (99)
GeRAL(92)SIOM(92)
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A g x-ray laser In x-ray laser Sn x-ray laser Sm x-ray laser Dy x-ray laser
W avelength 14 .0 nm 12.6 nm 12.0 nm 7.3 nm 5.8 nm
Gain Coefficient 7.2 cm-1 9.0 cm-1 11.5 cm-1 8.4 cm-1 8 .9 cm-1
Divergence angle 2.1 mrad 2.2 mrad 2.7 mrad 1.2 mrad 1.6 mrad
Deflection angle 4.5 mrad 0.9 mrad 1.2 mrad 1.0 mrad 1.4 mrad
Output Energy 90 µJ 300 µJ 690 µJ 313 µJ 500 µJ
Output Intensity 6.9x1010 W ·cm-2 8.0x1010 W ·cm-2 9.7x10 10 W ·cm-2 2.0x1011 W ·cm-2 3 .0x1011 W ·cm-2
Conversion Efficiency 6.0x10 -7 2 .0x10-6 9 .0x10 -6 2 .1x10-6 6 .0x10-6
Charateristics of X-ray Lasers国家
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Requirements for Divers
100 kJ, 20 ps to 1 ns, 120 TW 10 beams of 74 cm diameter 527 nm, 351 nm (large KDP crystals) Dismantled in 1999
Nova laser system:
Saturated operation of x-ray laser using~ kJ drive energy
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Requirements for Drivers
1 ns, 2.6 kJ, 2.6 TW, 1054 nm
< 1 ps, 100 TW, 1054 nm
1 kJ, 527 nm Nd:glass disk amplifier
Vulcan laser facility:
Saturated operation of x-ray laser using~ 100J drive energy
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Advantages of low driving energy requirementsProposed by Afanasiev, Shlyaptsev (1989)Demonstrated by Nickles, et al (1995)Prepulse + ∼1 ps, 1-10 J pumping
Transient Collisional Excitation (TCE), Table-Top XRLs
Gain Saturation Regime for Laser-Driven Tabletop, Transient Ni-like Ion X-Ray LasersDunn et al, Phys. Rev. Lett. 84, 4834 (2000)
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TCE Requirement for Driver Systems
Wavelength: 1054nm, 5 J, 5 ns; 5 J, 1 ps, 0.0017 Hz
COMET laser facility: Saturated operation of x-ray laser using~ several J drive energy
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Longitudinal Pumping
Highly Directive 18.9 nm Ni-like Mo XRL at 150 mJ PumpingOzaki et al, Phys. Rev. Lett. 89, 253902 (2002)
Demonstration of a Hybrid Collisionally Pumped Soft XRLJanulewicz et al, Phys. Rev. A 63, 033803 (2001)
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Grazing Incidence Pumping (GRIP)
Target
optimum gain region
On-axisx-ray laser
Preformed plasma1 ps Grazing
Incidence Pumping
200 ps
Wavelength: 800nm Short pulse duration: 80 fsLow Power: 300 mJ @ 10 Hz High Power: 15 J @ 2 shots/hr
High-Repetition-rate Grazing-Incidence Pumped X-Ray Laser Operating at 18.9 nmR. Keenan et al, Phys. Rev. Lett. 94, 103901 (2005)
GRIP COMETParameters XRL XRLPump (J): 150 mJ 5 JXRL (J): 10 nJ >10 µJPhotons: 109 1012
Rate (Hz): 10 0.004λ (nm): 18.9 12 - 47Source (µm2): 9 ´20 25 ´100Div. (mrad2): 3 ´5 2.5 ´10Pulse (ps): 2 2 - 8Peak B*: 2.0 ´1023 1.6 ´1025
Average B*‡: 3.7 ´1012 1.3 ´1011
* [Ph. mm-2 mrad-2 s -1 (0.1% BW) -1]‡ For 10 Hz operation
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Grazing Incidence Pumping (GRIP)
1. Grazing-incidence pumping scheme helps increase the path length and energy absorption efficiency
2. Each partition of the 300ps pulse is reflected and dump most of its energy at the turning point
3. Long gain region with a shallow electron density gradient
GRIP advantages:国
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Preformed plasma:
Grazing Incidence Pumping (GRIP)
Modulations of electron density:
• Peak intensity is 1x1011W/cm2
• Peak time is 360ps• 5ns delay time • Prepare an initial plasma (no Ne-like ions)
Second grazing incidence prepulse preparing the plasma
Comparison of density profilesIn normal incidence scheme andIn grazing incidence scheme.
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Grazing Incidence Pumping (GRIP)
Modulations of electron density:
1. Optimum intensity 3x1014W/cm2
2. Maximum gain coefficient happens at the turning point of the main pulse, the same spatial position as the valley 2
3. Valley 2 can work as a channel for the propagation and amplification of x-ray laser beams
De
Gain
Near-field Far-field
Field distributionof xrl beam
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Requirements for Drivers
Wavelength, Pulse width: 800nm, 80 fsEnergy @ 1ω : 300 mJ @ 10 Hz;
15 J @ 2 shots/hrIntensity (25µm x 1.0 cm): 1015 W cm-2;
5 x 1016 W cm-2
LLNL JANUSP laser:
Saturated operation of x-ray laser at 18.9 nm ~ 150mJ drive energy
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2001年-建成20TW飞秒激光装置—极光二号
640mJ/30fs, 20TW=2x1013W, 聚焦功率密度 >3x1019W/cm2
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2006年将建成200TW飞秒激光装置—极光三号
6J/30fs, 200TW=2x1014W, 聚焦功率密度 >3x1020W/cm2
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Discharge Pumped Table-Top XRLs
Discharge pumped H2 laser at 116.1 nm (Waynant, 1972) Discharge pumped Ar laser at 46.9 nm (Rocca et al., 1994)Saturated amplification (1996) Repetitive operation (1998), Application to plasma diagnostics (1998) Full spatial coherence (2000) Desk-top XRL (2002)
Full Spatial CoherenceLiu et al, ICXRL-2000, Pr2-123.
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Saturated XRLs国家
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More efficient XRLs with higher repetition rate
Require evaluation of different pumping geometries for x-ray lasers
Pu
mp
ing
En
erg
y (J
) Rep
etition
Rate (H
z)
Matthews 5 kJ 1984Nilsen 1 kJ 1993Zhang 150 J 1997Nickles 10 J 1997Tommassini 30 J 1999Li 0.15 J 2000Sebban 0.5 J 2001Ozaki 0.15 J 2002
XRL Pump Energy, Rep. Rate Efficiency vs Pumping Pulse Duration
Work Pulse Year Efficiency, εDa Silva 200 ps 1993 1.5 x 10-6
Zhang 75 ps 1997 6 x 10 -7
Warwick 7 ps 1998 1 x 10 -6
Dunn 1.2 ps 2000 1.7 x 10 -6
Sebban 35fs 2001 7 x 10 -8
Sebban 30 fs 2002 2 x 10 -8
Keenan 1.5 ps 2004 7 x 10 -8
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Demonstrated Applications
Main characteristics:
High brightnessHigh coherenceShort pulseShort wavelengthsHigh penetration
Main applications:
Microscopy Science, 258, 269 (1992)
Holography Science, 238, 517 (1987)
Radiography PRL, 76, 3574 (1996)
Deflectometry Science, 265, 514 (1994)
Interferometry Science, 273, 1093 (1996).
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Two-dimensional plasma-imaging
X-ray-laser-backlit image of an accelerated foilShort pulse duration is required togive high spatial resolution
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X-ray laser interferometer for probing high-density,long-scale length plasmas
Electron density measurements of high density plasmas using soft XRL interferometryDa Silva et al, Phys. Rev. Lett. 74, 3991 (1995)
Picosecond X-Ray Laser Interferometryof Dense PlasmasR. F. Smith et al, Phys. Rev. Lett. 89, 065004 (2002)
Shorter wavelengths, high spatial conference are required.
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X-ray microscope images of rat sperm nucleiprepared using different rechniquesShort wavelengths in the Water Window required
Resolution ~ 550
X-ray laser microscopy of biological samples国家
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Applications to Material Science
Time-resolved photoelectron spectroscopyNelson et al, Proc. SPIE 5197, 168 (2003)
Electric field induced surface changeZeitoun et al, Nucl. Inst. Meth. A 416, 189 (1998)
Surface modification with intense XUV irradiationRocca et al, Proc. SPIE 5197, 174 (2003)
Phase transition of ferroelectric domainsTai et al, Phys. Rev. Lett. 89, 257602 (2002).
106℃118℃119℃120℃121℃
24℃
130℃
(a)
(b)(c)(d)(e)(f)
(g)
(h)
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X-ray laser radiography
Measurement of single mode imprint by EUV laser radiographyWolfram et al, Phys. Plasmas 5, 227 (1998)
0 10050 150 0 10050 150 0 10050 150
0-25 25 0-25 25 0-25 25
Position at target (µm)
Mode number (200 µm square)
a) 2ω static RPP b) 2ωSSD c) 2ω ISI
XUVradiograph
2-D FFT ofradiograph
X-ray laser radiography of thin foilsimprinted by different smoothing techniques
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101
102
103
104
10-15 10 -14 10-13 10-12 10-11 10-10 10-9 10-8 10-7
X-ray lasers
Time (s)
•Fundamental processes in Femtosecond time scale: Molecular dynamics, spin dyn. Lattice dyn. Etc.Unexplored areas
•Shorter wavelengths:applications in wider areas of sciences
Science 274, 201(1996)
Future Direction of Plasma XRLs国家
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Summary
FEL X-ray Lasers and Plasma X-ray lasers are Allies
towards the same goals and for similar user community
Many technologies to share
high synchronization, stability, phase control etc
More Close Collaboration between Two Families is expected
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