Beam Plasma Physics Experimentsat ORION

Mark Hogan

 SLAC

2nd ORION Workshop February 18-20, 2003

Outline

•Large Fields Show Large Promise in Beam-Plasma Physics

•Highlights of Recent Experiments

•Example Experiments

•Look towards the Working Group asking how some of the open

questions might be addressed at ORION

2nd ORION Workshop February 18-20, 2003

Recent Results III: Promise and Challenge

ORION researchers over the past few years, developed a facility for doing

unique physics, and also many of the techniques and the expertise necessary

for conducting next experiments

E-157 & E-162 have observed a wide range of phenomena with bothelectron and positron drive beams:

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e- & e+ Focusing Wakefield acceleration

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e=1.31014 (cm-3)

ne=1.61014 (cm-3)

ne=2.01014 (cm-3)

ne=(2.3±0.1)1014 (cm-3)

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BPM data

(m

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(mrad)

1/sin

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Electron Beam Refraction at the Gas–Plasma Boundary

o BPM Data

X-ray Generation

– Model

Phys. Rev. Lett. 2002, 2003

Nature 2002 Phys. Rev. Lett. 2002

To Science 2003

Laser Wake Field Accelerator(LWFA)

A single short-pulse of photons

Self Modulated Laser Wake Field Accelerator(SMLWFA)

Raman forward scattering instability

Plasma Beat Wave Accelerator(PBWA)

Two-frequencies, i.e., a train of pulses

Concepts For Plasma-Based AcceleratorsPioneered by J.M.Dawson

Plasma Wake Field Accelerator(PWFA)

A high energy electron (or positron) bunch

evolves to

Research into “advanced” technologies and concepts that could provide the next innovations needed by particle physics. In many cases one is applying or extending physics and technology that is its own discipline to acceleration (ex. plasma physics, laser physics…). Active community investigating high-frequency rf, two-beam accelerators, laser accelerators, and plasma accelerators.

A 100 GeV-on-100 GeV e-e+ Collider

Based on Plasma Afterburners

50 GeV 50 GeV ee--

50 GeV 50 GeV ee++

e-WFA e+WFA

IP

LENSES

Afterburners

3 km

30 m

But can it lead to…?

Many Issues Need to Be Addressed First

1. Development of plasma sources capable of producing densities

> 1016 e-/cm3 over distances of several meters.

2. Quantify limitations of plasma lenses due to chromatic and spherical

aberrations.

3. Stable propagation through such a long high-density ion column –

beam matching and no limits due to electron hose instability.

4. Preservation of beam emittance

5. Accelerating gradients orders of magnitude larger than those studied

to date – via shorter bunches and optimized profiles.

6. Beam loading of the plasma wake with ~ 50% charge of the drive

beam

In fact, these issues will need to be addressed for many applications of beam plasma interactions

Many advances in recent years…

E-150: Plasma Lens for Electrons and Positrons

Phys. Rev. Lett. 87, 244801 (2001)

Built on early low-energy demonstration experiments in early to mid-nineties:FNAL (1990), JAPAN (1991), UCLA (1994)…

Demonstrated plasma lensing of 28.5GeV beams

UCLA

LINEAR PWFA SCALING

Ez ,linear N

z2

kp z 2 or np 1

z2

However, when nb > np, non-linear or “blow-out” regime

Scaling laws valid?

Ez: accelerating fieldN: # e-/bunchz: gaussian bunch lengthkp: plasma wave numbernp: plasma densitynb: beam density

For and

++++++++++++++ ++++++++++++++++

----- --- ----------------

---- -----------

-------- ------- -------------------- - -

-

---- - -- ---

------ -- -- ---- - - - - - --

---- - -- - - - --- --

- -- - - - - -

---- - ----

------

electron beam

+ + + + + + + + + + ++ + + + + + + + + + + + + + ++ + + + + + + + + + + + + + +

+ + + + + + + + + + + + + + +-

- --

--- --

EzEz

Accelerating Decelerating

Short bunch!

kp r 1

E-157, E-162, E-164 and E-164X:All (e- or e+) Beam Driven PWFA

UCLA

Located in the FFTB

e- or e+

N=2·1010

z=0.6 mmE=30 GeV

IonizingLaser Pulse

(193 nm)Li Plasma

ne≈2·1014 cm-3

L≈1.4 m

CerenkovRadiator

Streak Camera(1ps resolution)

X-RayDiagnostic

Optical TransitionRadiators Dump

25 m

∫Cdt

FFTBNot to scale!

Spectrometer

E-162, E-164 & E-164X:Common Experimental Apparatus

A quick reminder of how we do these experiments in the FFTB…

UCLA

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e-

e+

ne=0 ne≈1014 cm-3

2mm

2mm

• Ideal Plasma Lens in Blow-Out Regime

• Plasma Lens with Aberrations

• OTR images ≈1m from plasma exit

Note: nx>ny

Plasma Focusing ofElectrons and Positrons

E-150 E-162 FFTB

G [T/m] > 106 >103 0.18

L [m] 0.003 1.4 1.12

Np [e-/cm3] 6.5x1018 2x1014 N/A

Regime N/A

np nb

nb np

Experiments at ORIONmay address limitations of plasma lenses

High de-magnification plasma lens could help determine the ultimate limitations of plasma lenses. For a plasma lens with length equal to the focal length the de-magnification is given by:

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02 p 2

2 2ncWant small emittance, large initial beam size, but enough beam density for blow-out

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K

K

*

Limitations due to geometric and chromatic aberrations: &

J. J. Su et al Phys. Rev. A 41, 3321 (1990)

UCLA

Plasma OFF

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BetatronFitShortBetaXPSI.graph

Plasma OFF

Plasma ON

Envelope

x (µ

m)

L=1.4 m

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N

=1810-5 m-rad

0=6.1 cm

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=50 µm

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0=1.16m

E-157 E-162 Run 2

Phase Advance ne1/2L Phase Advance ne

1/2L

x (µ

m)

Beam matched to the plasma when: beam 2

p

c 2plasma

- Matching minimizes spot size variations and stabilize hose instability- Places a premium on getting small spots

Physical Review Letters 88, 154801 (2002)

Stable Propagation ThroughAn Extended Plasma

No significant instability observed in E-162 with

np up to 21014 cm-3, and L=1.4 m

- Hose instability grows as1 exp((kL)2/3), where k=p/(2)1/2c=(npe2/e0me 2)1/2c

– E-162: np=21014 cm-3, L=1.4 m => e4.5=92

– E-164: np=61015 cm-3, L=0.3 m => e5.4=227

– E-164X: np=21017 cm-3, L=0.06 m => e5.4=227

1. Phys. Rev. Lett. 67, 991 (1991)2. Phys. Rev. Lett. 88 , 125001 (2002)

Stable Propagation Part II

no significant growth expected (?)

- Theory assumes a preformed channel, neglects return currents…

- Simulations include these effects and also predict little growth2

Electron Hose Instability?

UCLA

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BPM data

(m

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(mrad)

1/sin

≈o BPM DATA

Impulse Model

rc=(nb/ne)1/2rb

Head

Plasma, ne

AsymmetricChannel

Beam Steering

SymmetricChannel

Beam Focusing

e-++

++

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+++++ + ++++- - - - - - - - -

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Core

E-157: Electron Beam Refraction At Plasma–Gas Boundary

P. Muggli et al., Nature 411, 2001

• Vary plasma – e- beam angle using UV pellicle

• Beam centroid displacement @ BPM6130, 3.8 m from the plasma center

UCLA

Refraction of an Electron Beam:Interplay between Simulation & Experiment

Laser off Laser on

3-D OSIRIS

PIC Simulation

Experiment(Cherenkov

images)

1st 1-to-1 modeling of meter-scale experiment in 3-D!

P. Muggli et al., Nature 411, 2001

UCLA

Phys. Rev. Lett. 88, 135004 (2002)

E-162: X-Ray Emission fromBetatron Motion in a Plasma Wiggler

Central Photon Energy = 14.2 keVNumber of Photons = 6x105

Peak Spectral Brightness = 7x1018

[#/(sec-mrad2-mm2-0.1%)]

V. Malka et al., Science 298, 1596 (2002)

200 MeV Laser Wakefield Resultsat Ecole Poly., France

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Sho t 12 (10 kG ) Sho t 26 (10 kG ) Shot 29 (5 kG )Shot 33 (5 kG ) Sho t 39 (2.5 kG) Sho t 40 (2.5 k G)

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ele

ctro

ns/

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tera

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E lectron energy (in M eV)

SM-LWFA electron energy spectrum

Accelerating Gradient> 100 GeV/m

Accelerating Gradient~200 GeV/m!

100 MeV Laser Wakefield ResultsA. Ting et al NRL

Plasmas Have Demonstrated Abilityto Support Large Amplitude Accelerating Electric Fields

Need guiding or other technique to extend interaction distance beyond a few mm

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Accelerated Tail ParticlesAverage Gradient ~ 70 MeV/m

Particles in the core nearly de-accelerated to zero!

PWFA Acceleration Experiments at ANL-AWA and FNL-A0

N. Barov et al, PAC-2001-MOPC010, FERMILAB-CONF-01-365, Dec 2001. 3pp

HeadTail

Simulation

UCLA

Head Head

Beam Driven PWFASingle Bunch Energy Transformer

OSIRIS Simulation

Average measured energy loss (slice average): 159±40 MeV Average measured energy gain (slice average): 156 ±40 MeV

(≈1.5108 e-/slice)

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ne=1.61014 (cm-3)

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Experimental Data

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A Few Examples of How

ORION Might Help Address Some of These Issues

Flexible Electron Source Opportunities for Plasma Wakefield Acceleration

• Bunch compression (R56 < 0) produces a ramped profile with a sharp cutoff high transformer ratio

/ (a.u.)p p

(a.u.)z

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Optimum profile

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PWFA with optimized drive bunch for transformer ratios (>2)

0-120 ps Vernier Delay

chicane

Fast kicker and septum

magnet

Combiner chicane(also compresses

drive pulse)

•Compressed, high-current 350 MeV drive pulse

•Narrow energy spread, 60 MeV witness pulse, with continuously variable delay

Drive and Witness Beam Production

HIGH ENERGY HALLNLCTA

1+1 ≠ 2:Simulation vs. Linear Superposition

2nd beam charge density

1st beam charge density

Linear superposition

Nonlinear wake

Nonlinear wake

Use Witness Bunch Capability to Study EffectsOf beam Loading on Accelerating Wake

Focusing Force Also Effected By Beam Loading

Focusing force on r=0.5c/Wp

2 beam charge densities

Linear superposition of focusing force

Simulation result

…and the Transverse (Focusing) Wake

Ion Channel Laser1:Proof of Principle at Optical Wavelengths

“Accelerator-based synchrotron light sources play a pivotal role in the U.S. scientific community 2. Free-electron lasers (FEL’s) can provide coherent radiation at wavelengths across the electromagnetic spectrum, and recently there has been growing interest in extending FEL’s down into the X-rays to provide researchers tools to understand the nature of proteins and chromosomes. … there is exciting potential for innovative science in the range of 8-20 keV, especially if a light source can be built with a high degree of coherence, temporal brevity, and high pulse energy. To date, the most promising candidate for such a source is a linac-driven X-ray FEL. It would be a unique instrument capable of opening new areas of research in physics, materials, chemistry and biology.

1 D. H. Whittum et al Phys. Rev. Lett. 64, 2511 (1990).2Report of The Basic Energy Sciences Advisory Committee Panel on Novel Coherent Light Sources,

Workshop at Gaithersburg Maryland, January 1999.http://www.er.doe.gov/production/bes/BESAC/NCLS_rep.PDF

Move beyond spontaneous x-rays to stimulated emission via the ICL (analogous to an FEL with plasma wiggler)

• Requires many betatron oscillations therefore lower energy beam with high density plasma

• 60MeV, 20cm long plasma of 6x1015 density for visible

• 300MeV, 1.5m long plasma of 4x1014 density for ultraviolet (80nm)

• ICL potential advantage over FEL:

• Short wavelength with relatively lower gamma – less linac, better coupling

• Shorter period and stronger wigglers via plasma ion column

Build on the experience of E-157/E-162/E-164 towards an ICL

r 22

1 K 2

2 ()2

K r0

c

Beam Plasma Experiments:Observed a wide range of phenomena but still much to do

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0=1.15m

e- & e+ Focusing Wakefield acceleration

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e=1.31014 (cm-3)

ne=1.61014 (cm-3)

ne=2.01014 (cm-3)

ne=(2.3±0.1)1014 (cm-3)

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eV)

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BPM data

(m

rad)

(mrad)

1/sin

≈

Electron Beam Refraction at the Gas–Plasma Boundary

o BPM Data

X-ray Generation

– Model

Still much to do: Quantify limits for plasma lenses due to chromatic and spherical aberrations Test for continued robustness against instabilities such as electron hose > GeV/m acceleration via shorter bunches and tailored longitudinal profiles Plasma source development: higher densities over several meters Extend radiation generation from spontaneous to stimulated emission via ICL Load the plasma wake and preserve focusing properties of the ion channel Load the plasma wake for acceleration with narrow energy spread and high extraction efficiency

Focusing of electron beams and stable propagation through an extended plasma Electron beam deflection analogous to refraction at the gas-plasma boundary X-ray generation due to betatron motion in the blown-out plasma ion column Large gradients (>100GeV/m) over mm scale distances Smaller gradients (~100MeV/m) over meter scale distances

We will focus on:• Plasma wakefield physics• Plasma lenses• Beam quality• Radiation generation• Instabilities• Shaped beams• Beam loading• Simulation and theory needs.Particularly relevant are:• Ideas for experiments at ORION• Ideas for diagnostics, instruments and models that could support/improve experiments.• Requirements for diagnostics, instruments, beams and models (whether or not you have an idea of how to make them) that would enable/improve experiments.

Redwood Room “?”

Prof. Tom Katsouleas WG Leader

2nd ORION Workshop February 18-20, 2003

Beam-Plasma Working Group