Laser-Plasma Acceleration WG

Eric Esarey, LBNLSergei Tochitsky, UCLA

AAC 2004 Experimental Results Laser-Plasma Accelerator WG

2MeV

Self-trapped

1x101

8 cm-3

2TW0.8mkm

SM-LWFA

KERI

Glass capillary

100 MeV

Self-trapped

6x1016 cm-3

30TW1.06 mkm

LWFA

Osaka University

2 TW beam for LIPA injector

Ponderomotivechannel

Integrated over 90 shots spectrum

Channel

40 MeV20 MeV38 MeV40 MeV7 ±1 MeV2 pC

78 ±2MeV20 pC

86 ±2 -150 MeV300 pC

>170±15MeV, 500 pC,

Energy Gain

Self-trapped

OpticalInjection ioniz.

12 MeVexternal

Self-trapped

Self-trapped

Self-trapped

Self-trapped

Self-trappedInjector type

1.4x1020

cm-31x1019 cm-3

1x1016 cm-3

1.8x1019

cm-3.1.5x1020

cm-32x1019 cm-

32x1019 cm-3

6x1018 cm-3Plasm.Density

20TW0.8 mkm2.x1019 W/cm2W0=5 mkm,, 23fs

10TW1.06 mkm3x1018 W/cm2W0=12 mkm, 500s

1TW10.3+10.6.mk

6TW0.8 mkm1x1019 W/cm2W0=6 mkm,50fs

2TW 0.8 mkm5x1018 W/cm2W0=5mkm,50fs

16TW0.8 mkm ,1x1018 W/cm2W0=25 mkm,40fs

8TW0.8 mkm,1x1019 W/cm2W0=7 mkm, 55fs

30TW0.8 mkm, 3x1018 W/cm2,W0=18 mkm, 30fs

Laser parrs

SM-LWFA

SM-LWFA

PBWASM-LWFA

SM-LWFA

SM-LWFA

SM-LWFA

SM(for-ced)LWFA

Scheme

JAERINRLNeptune, UCLA

University of Tokio

AISTRAL-alphaX

LBNLLOA

Experimental Set-Up

Energy: 360 - 540mJ (50% in focal spot)

Pulse Duration: 40fs (FWHM)

Focal Spot Diameter: 25 µm

Vacuum Intensity: 9 x 1017 - 2 x 1018 Wcm-2

a0 : 0.7 - 1.0

Breakthrough: 85 MeV e-beam with %-level energy spread from laser accelerator (LBNL)

UnguidedBeam profile Spectrum

Charge~100 pC

# e/

MeV

]

70 75 80 85 90

Charge>100 pC

2-5 mrad divergence

Guided

Energy [MeV]

Charge in [150-190] MeV : (500 ±200) pC

Recent results on e-beam :Energy distribution improvements

V. Malka (LOA)

Recent results on e-beam :Energy distribution improvements

N.B. : color tables are different

Results (C.Murphy, IC/RAL)

0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

1.0E+06

0 25 50 75 100

Energy (MeV)

PSL

per

rel

ativ

e en

ergy

spr

ead

• Electron Spectrum:– A single mono-

energetic feature over the top of an exponential observed at energies in excess of 50MeV

– Underestimate of energy due to neglect of fringe fields

AIST

Electron Energy Spectrum including quasi-monoenergetic beam

Electron Energy Spectrum including quasi-monoenergetic beam

104

105

106

107

108

0 5 10 15 20 25 30Ele

ctro

n N

umbe

rs (/

MeV

/sr/

shot

)

Electron Energy (MeV)

100

101

102

103

104

600 700 800 900 1000 1100 1200 1300

Inte

nsity

(arb

.uni

t)

Wavelength (nm)

1st-Stokes

Laser Wavelength

K.Koyama (AIST, Japan)Monoenergetic beam was emitted in an narrow divergence angle.

Production of a Monoenergetic Beam

1. Excitation of wake (e.g., self-modulation of laser)2. Onset of self-trapping (e.g., wavebreaking)3. Terminatinon of trapping (e.g., beam loading)4. Acceleration

If > dephasing length: large energy spreadIf < dephasing length: monoenergetic

Wake Excitation Trapping Laccel ~Ldephas~1/ne

1 2-3 4

Optimal choice of the plasma density: the smallest possible densityFor conditions 1 -4 to be fulfilled.

2D PIC Code (W. Mori,UCLA)

Beam loading of first bunch contributes to the generation of a second bunch

( ˆ k )

( ˆ e )

( ˆ b )

Electron Energy of ~1GeV range observed in our 3D channel simulation

• (3D) Maximum Energy = 840 MeV (over a distance .84 cm)

• 2 acceleration stages, the first bunch reaches ~500MeV then dephases. The second bunch achieves much higher energies (~840MeV)

•2D Simulations only has 1 group of fast electrons

• 2D simulations underestimate maximum energy gain

• 2D simulations overestimate accelerated charge

Ultra-Intense Laser is illuminated into a glass capillary, which accelerates plasma electrons to 100 MeV

Y.Kitagawa-Osaka

10 mm

ALaser guide

Glass capillaryEl

ectr

ons

/MeV

/str

108

109

1010

1011

1012

1013

1014

1 10 100

10 mm long

1.2 mm

Detection limit

Bump

PRL Vol.92, No.20 (2004)Energy [MeV]

1

100

10 4

10 6

10 20 30 40 50Energy (MeV)

Ele

ctro

ns/M

eV

Noise Level

UCLAUCLA

1.3 GeV/m x 0.03 m

ω1- ω 2= ωplasma 10.3 µm - 10.6 µm=340 µm or ≈1 THz

Injection of an electron beam into a 3-cm long ponderomotively formed plasma channel

Surface BarrierDetectors

F/18 1 TW CO2 Laser Beam

I ~ 5 x1014 W/cm2

ElectronSpectrometer

Camera

n e=

1016

cm-3

F/75 12 MeV e- beam

30 mm

PBWA Phase II

∆E/E ~10%

10-ps e-bunch

100-fs prebunched, phase-locked e-beam

S. Tochitsky et al, PRL, March, 2004

Enhanced acceleration of externally injected electrons in a PBWA

Scaling Laws for LWFA

One of many 1 GeV scenarios

Next step: 1 GeV compact module100 TW laser + plasma channel

L'OASIS Laser technology

Electron injector

Plasma channel e- beam

< 3mm < 10 cm

1-3 GeVLaser

100 TW, 40 fs10 Hz

1016-1018 cm-3

Plasma channel technology

+

High energy e-beams

Femtosecond x-rays

THz radiation

Radio-isotopes