Recent Work on

Laser and Beam – Driven Wakefield Acceleration

Chan Joshi University of California Los Angeles USA

SupportedbyUSDOE,

BIG PHYSICS GETS SMALL

UCLA Program on Plasma Based Accelerators

C. Joshi, P.I. W. Mori, Co-P.I.

C. Clayton, Co-P.I. 2005-Present

EXPERIMENTS Dr. Chris Clayton Dr. Sergei Tochitsky Ken Marsh Jay Sung, Neptune Lab, graduated Joe Ralph, Neptune Lab, graduated Fang Fang, Terawatt Lab, graduated Dan Haberberger, Neptune Lab Art Pak, Terawatt Lab Tyan-lin Wang, LLNL 2 students to be recruited for SLAC

Collaborators: Professors Musumeci, Rosenzweig & Pellegrini ( UCLA) Dr. M. Hogan (SLAC) Professors T. Katsouleas, P. Muggli ( Duke & USC ) Dr. Dustin Froula (LLNL) Professor Luis O Silva ( IST )

THEORY & SIMULATIONS

Prof. Warren Mori Chengkun Huang, graduated Wei Lu, graduated Miaomiao Zhou, graduated M.Tzoufras , graduated Weiming An

Alumni of UCLA Plasma Accelerator Group Still active in Plasma Acceleration (1985- present)

C.E..ClaytonUCLA(1983‐present)T.Katsouleas,DeanofEngineeringDukeUniversity(1984‐1989)WarrenMori,ProfessorUCLA(1982‐present)DonUmstadter,ProfessorU.Nebraska/U.Michigan(1982‐1987)WimLeemans,HeadL’OasisLabLBNL(1987‐1991)YoniyoshiKitagawa,ProfessorOsakaU/Hama’tsu(1988‐1989)RonWilliams,ProfessorFA&M(1986‐1992)PatricMuggli,ResearchProfessorUSC(1992‐1996)DanGordon,NRL(1992‐1997)CatalinFilipSpectraPhysics(1997‐2003)LuisOSilvaProfessorISTPortugal(1995‐1998)WeiLu,ResearcherUCLA(2000‐2006)ChengkunHuang,ResearcherLANL(2001‐2007)J.Ralph,ResearcherLLNL(2001‐2008)M.TzoufrasOxford(2000‐2007)

AlsoJ.M.Dawson,F.F.Chen,TTajima,P.Chen(Priorto1985)

Plasma Based Accelerators

Plasma Wake Field Accelerator A high energy electron bunch

•  Laser Wake Field Accelerator A single short-pulse of photons

•  Drive beam

•  Trailing beam

•  Wake: phase velocity = driver velocity

Vgr

T.TajimaandJ.M.DawsonPRL(1979)P.Chenet.al.PRL(1983)

Largewakeforalaseramplitudeao=eEo/mωoc ~ 1orabeamdensitynb~ no

Forτpulseoforderπωp‐1~100fs(1017/no)1/2andspot

sizec/ωp:

P~15TW(τpulse/100fs)2laser

  Ion channel formed by complete evacuation of plasma electrons

  Ideal linear focusing force   Uniform acceleration in transverse dimension

Blowout and Bubble Formation Regime Rosenzwiegetal.1990PuhkovandMeyer‐te‐vehn2002

Nodephasing Significantdephasing

Intense Beams of Electrons for Plasma Wakefield Acceleration

N=4x1010

Energy50GeV

RepRate60HZ

Energy/pulse320JFocalSpotSize10microns

PulseWidth50fs

FocusedIntensity7x1021W/cm2

Comparabletothemostintenselaserbeamsto‐date

Onlyplaceintheworldtostudythistopic!!

Collaborators

Page 7

PWFA :

Experimental Setup

e- spectrumX-ray basedspectrometer

e- beamfrom SLAClinear accelerator

e- bunch lengthautocorrelation ofcoherent transition

radiation (CTR)

e- spectrum?erenkov light

in air gap

e- spatialdistribution

optical transitionradiation (OTR)

trapped particles

plasma

oven

notch

collimator

?erenkov

cell

spectrometer

magnet

beam

stopper

imaging?erenkovmonitor

spectro-graph

30‐40GeV

10‐100GeV

Energy Gain Scales Linearly with Length

PLASMALENGTH(cm)

0 10 20 30

BREAKING THE 1 GeV BARRIER

M.HoganetalPhysRevLeX(2005)

Nophaseslippagebetweenpargclesthemselvesandbetweenpargclesandwake

Energy Doubling of 42 Billion Volt Electrons Using an 85 cm Long Plasma Wakefield Accelerator

Nature v 445,p741 (2007)

42GeV 85GeV

Spectacular Progress in Plasma Wakefield Acceleration

RAL

LBLOsaka

UCLA

E164X

ILC

ANL

Plasma Accelerator Progress “Accelerator Moore’s Law”

E167

LBNL

WorkingMachinesDoingphysics

Max.EnergyinExperiments

E+

E-

driver

load

Generation of High Quality Beams

Themostpressinggoalisthedemonstra_onofonestageofa10‐25GeVplasmaacceleratormodulewithsmallenergyspread&emiXanceandatleast1nCcharge.

FACET : Facility for AA Research @SLAC

Beam-Plasma Accelerators: Where to next?

Laser Wakefield Accelerator Limits to Energy Gain W = eEzLacc

•  Dephasing:

•  Depletion: For a0 > 1 Ldph~ Ldepl

€

Ldif ≅ πLR = π 2w02 /λ

order mm! (but overcome w/ channels orrelativistic self-focusing)

cVgr

€

Ldph =λp 2

1−Vgr corder 10 cm x 1016/no

•  Diffraction:

Needtoincreasetheelectron‐wakeinterac_onlength

Self Guiding Could Simplify GeV- Class LWFA

•  Self-Guiding of Laser Pulses in the Blowout Regime J.Ralph et al PRL 102,175003 (2009)

•  Quasi-Monoenergetic Electron Acceleration to 720 MeV using Callisto Laser at LLNL.

D.Froula et al to be published PRL (2009)

•  Ionization Induced Trapping for Injecting electrons in Low Density Wakes.

•  A.Pak et al PRL submitted (2009)

. Experiments for Extending the Self-Guided Regime to beyond 1 GeV. ( UCLA/LLNL collaboration : Unpublished )

Pulse evolution is minimized if this is satisfied. For W0 close to this size the pulse is predicted to reach a steady state at Wmatched

Self-Guiding in the Blow-Out Regime

1. W. Lu, C. Huang, M. Zhou, M. Tzoufras, F. S. Tsung,W. B. Mori, and T. Katsouleas, Phys. Plasmas 13, 056709(2006)

€

δnn

≥

4k pW0( )2

⇒ k pW0( ) ≥ 2GuidingCondigon:

MatchingCondigon1:

This gives a minimum density where self-guiding can occur for a given W0

02 aWkRk matchpbp ≈≈

Matchedspotsize

BlowoutCondigon:

€

ao > 2

Theaccelera_ngstructureneedstoremainasstable, for this purpose we choose the laserspotsizeandintensityfromthecondi_on:

The accelera_ng field in the ion channeldecreases linearly from the front reachingminimumvaluewithmagnitude:

Theaccelera_onprocessislimitedbydephasing:

Physical picture of Self guided LWFA

Parameter design for GeV and beyond for LWFA

P(PW) τ(fs) np(cm‐3) w0(µm) L(cm) a0 Q(nC) E(GeV)

0.100 60 2.0×1018 15 0.9 3.78 0.40 1.06

0.250 60 1.0×1018 20 1.0 3.15 0.30 2.0

WeiLuet.al.PRST‐AB07

Callisto Laser at LLNL : 300 TW Maximum Power

Current

Planned

Collaborators

•  D.Froula•  F.Albert•  P.Michel•  L.Divol•  T.Doeppner•  J.Palastro•  J.Bonlie•  D.Price

LLNL

•  C.Clayton

•  K.Marsh

•  A.Pak•  W.Lu

•  J.Ralph

•  S.Margns

•  W.Mori

•  C.Joshi

UCLA

ThisworkwasperformedundertheauspicesoftheU.S.DepartmentofEnergybyLawrenceLivermoreNagonalLaboratoryundercontractDE‐AC52‐07NA27344.

•  B.Pollock•  J.S.Ross

•  G.Tynan

UCSD

D.Froulaetal,PhysRevLeXs,accepted(2009)

J.RalphetalPhysRevLeXs(2009)

A.Paketal,PysRevLeXs,SubmiXed(2009)

Self-Guiding in the Blow-Out Regime

J.RalphetalPhysRevLejs(2009)A.G.R.ThomasPRL(2007)

Self-Guiding in Blow-Out Regime

LaserSpotatentrance

LaserSpotatExit:NoPlasma

PICSimulagonMatchedBeamGuiding

GuidedSpotAtExit:Simulagons

GuidedSpotatMatchingCondigon

Lessthanmatched

Closetomatched

Greaterthanmatched

Foragivenaoandlaserspotsizematchingachievedbyvaryingplasmadensity

€

kpRb ≈ kpWmatch ≈ 2 a0

Transmitted Laser Spectrum at Matched Density Confirms Self-Guiding

IncidentLaser

TransmijedImagedLaserspectrum

PhotonDecceleragonPhotonAcceleragon

J.RalphetalPhysRevLejs(2009)

Pump Depletion Limited Guided Beam propagation of Ultra- short, Intense Laser Pulses

Capabili_esWavelength 806nmContrast ~105Energy >15JPulsewidth <60fsReprate 2/hour

The UCLA/LLNL collaboration : 200 TW Callisto Laser Facility at the Jupiter Laser Facility @ LLNL

20fsOscillator/PulseStretcher

Self Guided LWFA on Callisto Laser @LLNL

Upto15Jin60fs,30%incentralspotMaximumpowerontarget:80TW

HeGasjet/GasCelltargets

DualScreenSpectrometer

D.FroulaetalPhys.Rev.LeXs.SubmiXed2009

Threshold for Self- Trapping in the Self-Guided Regime Measured

TrappingThreshold

~3

SaturatedCharge

~5

40TWCoupledtoWake

Simulagons

Experiment

D.FroulaetalPhys.Rev.LeXs.Accepted2009

A self-injection density threshold is measured at 3x1018 cm-3

Themeasuredself‐injecgonthreshold(3x1018cm‐3)limitsenergygaintolessthan1GeV

•  Image plates are absolutely calibrated for charge

•  No electrons were self-injected and accelerated above 100 MeV at densities less than 3x1018 cm-3

P=65TW

0

0.1

1

10

100

1000

0 1 2 3 4 5 6Densityx1018(cm‐3)

Charge(p

C)

Froulaet.al.Phys.Rev.Lej.(2009)

Theenergyintheelectronbeamsweremeasuredtoincreaseastheelectrondensitywasreduced

The energy is measured to increase with decreasing density and agrees

well with analytical scaling*

No electrons were accelerated beyond 100 MeV for densities less than 3x1018 cm-3

3‐mm120MeV

5‐mm350MeV

8‐mm720MeV

Electron

Ene

rgy

Electron

Ene

rgy

Electron

Ene

rgy

0

0.5

1

1.5

2

0 2 4 6 8 10Densityx10 18(cm ‐3)

Max.Ene

rgy(GeV

)

*W.LuPRSTAB(2006)

P=75TW

3x10186x10189x1018

Density(cm‐3)

Ionization Induced Trapping in Laser-Produced Wakes

•  Usetraceatomswithalargestepinionizagonpotengal

•  Weuse9:1He:Nitrogenmix.•  ThetwoHeelectronsandthe

first5(L‐shell)Nelectronsformthewake

•  The6th(Kshell)nitrogenelectronisionizedinthewakeandtrappedmoreeasilybythewakepotengalthantheelectronsthatsupportthewake.

•  Ionizagontrappingreducesthewakeamplitudeandthereforethelaserpowerneededtotrapelectrons.

E.OzetalPRL2007A.PaketalsubmijedPhysRevLej(2009)T.R.Rpwland‐ReesetalPRL(2006)

Threshold Behavior Consistent with Ionization Induced Trapping in LWFA

9:1He:N2Plasma

Nochargebelowaoof2.3inpureHeplasma A.PaketalsubmijedPhysRevLej(2009)

Tunnel Ionization of Nitrogen K-shell Electrons into LWFA

9:1He:N2Plasma

PICSimulagonsExperiment

A.PaketalsubmijedPhysRevLej(2009)

Ionization Trapping Signature in Transmitted Laser Spectrum

AddigonalBlueShin

HePlasma 9:1He:N2Plasma

IonizagonofthesixthNitrogenelectroninsidethewakeproducesaddigonalblueshin

A.PaketalsubmijedPhysRevLej(2009)

Measurement of Beam Divergence in Plane of Laser Ionization Induced Injection and Trapping

Diagnosis of the Plasma and the Wake in a 1.4 cm Long Gas Cell

Interferometry

ExitSpotSizeandImagedSpectrum

K-Shell Electrons of Oxygen Injected into Wakes

100MeV

500MeV

1000MeV

2000MeV

Energy

Uptp2.5pCofchargeabove1GeVMaximumEnergy1.7GV

10‐5

0.0001

0.001

0.01

0.1

1

0.1 1Energy(GeV)

Charge/M

eV

3x1018 1x1018 1x1018

50TW 50TW 85TW

Continuous electron spectra are measured with a 3% CO2 mixture

This collaboration has pushed the limits of energy gain in LWFA while demonstrating the limitations of self-injection

The electron energy is measured as a function of plasma length

The density is reduced to match the plasma length to the dephasing

length

TrappingThreshold3x1018cm‐3

1.5x1018cm‐3

5mm 8mm 14mm

100MeV

500MeV

1000MeV

2000MeV

Ionizagoninducedtrapping

0

500

1000

1500

2000

2500

2 4 6 8 10 12 14 16En

ergy m

ax(M

eV)

PlasmaLength(mm)

Self‐Injecgon

PlasmaLength

Energy

LLNL/UCLACollabora_on:Unpublisheddata

He He He:CO2

Two-stage simulations demonstrate monoenergetic 1.5 GeV electron beams using the Callisto laser conditions : 80 TW

OSIRIS simulations were used to design a two-stage density profile

for future Callisto experiments

Two-stage injector produces a 1.5 GeV monoenergetic electron beam

Callisto experimental parameters were used in this simulation

No self-injection occurs at these conditions; trace amounts of O2

provide injection

0 0.75 1 5

1.5x1018ccHeGas

mm

InjecgonStage1.5x1018cc

97%He+3%O2Gas

15

1.5cmAcceleragonStage

Energy(GeV)

0 0.5 1 1.5

Charge(a

rb.u

nits)

LLNL/UCLACollabora_on:Unpublisheddata

Summary on LWFA

•  Amatchedlaserpulsecanbeselfguided

inaplasmaoverdistancesofinteresttoobtainelectronenergiesinthe1+GeVrange.

•  Needlaserpowerontheorder100TW•  Self‐trappingmaybedifficultatdensi_esontheorder1e18

cm‐3.

•  Ioniza_oninducedtrappingmaybeapromisingwayofinjec_ngelectronsinlowdensitywakes.

Conclusions

BothbeamdrivenandlaserdrivenPlasmawakefieldAccelera_onconceptshavemade

remarkableprogress.

RobustGeVscaleLWFAwithingraspwith100TWlaserusingself‐guidedregime.

Expectmucheffortincontrollinginjec_on,beamloading,andemiXanceinthenextfewyears.

John M. Dawson1930-2001

“ThisisastoryofScienceasaLivingThingtakingUnexpectedturnsindirec_onsthatwereneverforeseen.Sciencemusthavegoals,butitmustAlsohavethefreedomtofollowupinteres_ngAndunexpectedresultswhentheyturnup.Thisiswhatexcitesthegoodyoungresearcheranditisintheirhandsthatourfuturerests.”

JohnDawsonAIPConf.Proc.560p3(2000)PersonalRecollecRonsontheDevelopmentofPlasmaAcceleratorsandLightSources

EPILOGUE

Par_cleSimula_onsofexperimentalcondi_onshowself‐guiding,injec_onandpeakenergy

• self‐injecgonoccursaner3mmofpropagagon

• Attheendofthe8.5mmsimulagon,aquasi‐monoenergegc760MeVelectronbeamisproduced