Compact radiation sources based on laser-

plasma wakefield accelerators

Silvia Cipiccia on behalf of Prof. Dino JaroszynskiUniversity of Strathclyde

Outline of talk

• Large and small accelerators + high power lasers• Laser driven wakes• Ultra-short bunch electron production using wakefield

accelerators • Initial FEL experiments• Betatron gamma ray source• Conclusion

CERN – LHCCERN – LHC27 km 27 km circumferencecircumference

• SLACSLAC

50 GeV in 3.3 km

20 MV/m

7 TeV in 27 km

7 MV/m

Large accelerators depend on superconducting Radio Frequency cavities and superconducting magnets

Synchrotrons light sources and free-electron lasers: tools for scientists

Synchrotron – huge size and cost is determined by accelerator technology

Diamond

undulatorsynchrotron

DESY undulator

The future of electron accelerators

27 Km circumference

2 miles long

Electrons energy:

50MeV - 1GeV

4 cm

High energy electron beams in few mm

…..

an industrial

revolution?

Plasma Replaces RF Cavities

Small Scale Source = Big Applications

Particles accelerated by electrostatic fields of plasma waves

Accelerators:

Surf a 10’s cm long microwave – conventional technology

Surf a 10’s mm long plasma wave – laser-plasma technology

2

max

2

3ga

[V/cm]E e n

Wakefield acceleration

p

Dephasing length: which gives a maximum energy:

0g

p

204 3 ,d g pL c a 2

0

2

3 ga

Modelling of Laser Wakefield Acceleration

laser pulse envelopeelectrostatic wakefieldbunch densityenergy density of wakefield

z-vg t (units of λp)Movie shows • laser pulse deforms as it transfers energy to the plasma and sets up wakefield • wakefield changes as a result of laser pulse deformation • electron bunch modifies wakefield as it takes energy from the plasma • electron bunch slips from a region of E>0 to E<0 and reaches max. energy

OSIRIS – PIC code developed by W. Mori and L. Silva OSIRIS – PIC code developed by W. Mori and L. Silva

Bubble Regime

Electron acceleration

• energy gain limited by dephasing, caused by difference between velocities of electron and wakefield

• scaling favours low plasma density

gwfel vvcv

12/32/1 pppdeph nnnLE

log(γ)

(fs) /c

electron orbit

pulse intensity

separatrix

note logarithmicenergy scale

Energy spread

accelerating wakefield

wakeenergy density

bunch density

at injection

(fs) /c

at dephasing

• energy spread induced by spatial variation of accelerating field along bunch• can be compensated for by combined effect of dephasing and beam loading • requires precise tuning of injection phase, bunch charge and bunch length

• during first half of acceleration, front of bunch gains more energy than rear → energy spread increases• during second half of acceleration, rear of bunch gains more energy than front → energy spread decreases and reaches minimum

210

BENDINGMAGNET

UNDULATOR

ELECTRON ENERGYSPECTROMETER

LASER IN

PLASMA ACCELERATOR

RADIATIONSPECTROMETER

8 m

TOPS laser: 1 J @ 10 Hz; = 800 nm; 30 fs

Jaroszynski et al., (Royal Society Transactions, 2006)

ALPHA-X Advanced Laser Plasma High-energy Accelerators towards X-rays

Experimental Results: energy stability

Electron Spectrometer: 200 consecutive shots (spectrum on 196 shots)

69 90 124 185Energy (MeV)

100 consecutive shotsMean E0 = (137 4) MeV

2.8% stability

Highest energy achievable at Strathclyde: 360 MeV in 2 mm

Narrow energy spread beams

100 110 120 130 140 150

8000

10000

12000

14000

16000

18000

Cha

rge/

unit

ener

gy [a

.u.]

Energy [MeV]

0.75%

63 MeV 170 MeV

Absolute energy spread < 600 keV

Strathclyde

Experimental Results – emittance

• divergence 1 – 2 mrad for this run with 125 MeV electrons• average N = (2.2 0.7) mm mrad• best N = (1.0 0.1) mm mrad• Elliptical beam: N, X > N, Y • Upper limit because of resolution

• Second generation mask with hole ~ 25 m and improved detection system

Experimental results: beam pointing

• 500 consecutive shots at Strathclyde• narrow divergence (~2 mrad) beam• wide divergence low energy halo• X = (7 3) mrad, Y = (3 2) mrad

• 8 mrad acceptance angle for EMQs• 25% pointing reduction with PMQs installed

-10

0

10

20

-10 0 10 20

Y[m

rad]

X [mrad]

no PMQs PMQs in

5 mrad

2 fs bunch measured at 1 m from source

Peak current several kiloAmperes

0 2 4 6 8 10 12 14 16 18

0.000000

0.000005

0.000010

0.000015

0.000020

0.000025

0.000030

0.000035

Measured TR signal 1 fs 1.5 fs 2 fs 2.5 fs 3 fs 4 fs

TR

(J/

m)

Wavelength (m)

Strathclydeexperiments in spring 2010

Experimental results:Bunch length measurements Coherent Transition Radiation

ALPHA-X Advanced Laser Plasma High-energy Accelerators towards X-rays

Compact R&D facilities to develop and apply femtosecond duration particle, synchrotron, free-electron laser and gamma ray sources

70 75 80 85 90 95 1000

250

500

750

1000

No

. ele

ctr

on

s/ M

eV

[a

.u.]

Electron energy [MeV]

(b)

(a)

electron beam spectrum

beam emittance: <1 mm mrad

CTR: electron bunch duration:

1-3 fs

0.7%

FEL

1J 30 fs

1019 cm-3

0 5 10 15

0.0

0.1

0.2

0.3

Measured TR signal 1 fs 1.5 fs 2 fs 2.5 fs 3 fs 4 fs

TR

(J/

m)

Wavelength (m)

= 2.8 nm – 1 m (<1GeV beam)

Extending to higher energy:Strathclyde plasma media

• Extend energy range to multi GeV

• Study plasma media – extend length relativistic self focussing, gas cells and channels

• Stable electron beam generation

4 cm

Gas Cell10 J, 50 fs

E0 = 690 MeV, / MEAS ~ 4%

E0 = 770 MeV, / MEAS ~ 4%

E0 = 610 MeV, / MEAS ~ 4.5%

RAL GEMINI: Measurements limited by spectrometer resolution – maximum energy measured 850 MeV

First undulator radiation demonstration with LWFA

• Strathclyde, Jena, Stellenbosch collaboration

• 55 – 70 MeV electrons

• VIS/IR synchrotron radiation

Schlenvoigt .., Jaroszynski et al., Nature Phys. 4, 130 (2008)

Gallacher, ….Jaroszynski et al. Physics of Plasmas, Sept. (2009)

• Measured / ~ 2.2 – 6.2%

• Analysis of undulator spectrum and

modelling of spectrometer

/ closer to 1%

Recent VUV radiation measurements at Strathclyde

Recent VUV radiation measurements at Strathclyde

Q = 3.1 pC;σγ/γ = 3.5% (limit of the spectrometer)

Recent VUV radiation measurements at Strathclyde

Radiation sources: Synchrotron and Free-Electron Laser (FEL): a potential 5th generation light

source• Use output of wakefield accelerator to drive compact synchrotron light source or FEL

• Take advantage of electron beam properties

• Coherent spontaneous emission: prebunched FEL I~I0(N+N(N-1)f(k))

• Ultra-short duration electron bunches: I >10 kA

• Operate in superradiant regime: FEL X-ray amplifier (self-similar evolution)

Potential compact future synchrotron source and x-ray FEL

Need a low emittance GeV beam with < 10 fs electron beam with I > 10 kA

Operate in superradiant regime: SASE alone is not adequate: noise amplifier

Need to consider injection (from HHG source) or pre-bunching

SCALING LAWS

• Betatron frequency: • Transverse momentum:• Divergence: • Critical photon energy:• Efficiency:

• Wavelength:

/ 2p

ea n r

/a 2

c eE n r

Betatron radiation emission during LWFA

/phot cycleN a

2 22 2

2 3/2

31 ( ) 1 ( )

2 2 2h e ee p e

a ac

h h

Synchrotron, betatron and FEL radiation peak brilliance

ALPHA-X ideal 1GeV bunch

FEL: Brilliance 5 – 7 orders of magnitude larger

ucm

n = 1 mm mrad

e = 1-10 fs

Q = 1 – 20 pC

I = 1-25 kA

< 1%

I(k) ~ I0(k)(N+N(N-1)f(k)) FEL = spontaneous emission x 107

betatron source

The Scottish Centre for the Application of Plasma Based Accelerators: SCAPA

1000 m2 laboratory space: 200-300 TW laser and 10 “beam lines” producing particles and coherent and incoherent radiation sources for applications: nuclear physics, health sciences, plasma physics etc.

Strathclyde Technology and Innovation Centre

Conclusions• Laser driven plasma waves are a useful way of accelerating charged particles

and producing a compact radiation source: 100 – 1000 times smaller than conventional sources

• Some very good properties: sub 10 fs electron bunches potentially shorter (< 1 fs?) and high peak current (up to 35 kA?), n < 1 mm mrad, < 1%?.

• Slice values important for FEL - potentially 10 times better. Wide energy range, wide wavelength range: THz – x-ray

• Good candidate for FEL – coherence & tuneability• Betatron radiation – towards fs duration gamma rays• Still in R&D stage – need a few years to show potential• Challenges: rep rate, stability, energy spread and emittance, higher charge

and shorter bunch length, beam transport• Synchronised with laser – can combine radiation, particles (electrons, protons,

ions), intrinsic synchronisation• A compact light source for every university or 5th Generation light source? A

paradigm shift?• Setting up a new centre of excellence: SCAPA: the Scottish Centre for the

Application of Plasma based Accelerators: based in Glasgow and part of a pooling effort: SUPA – The Scottish Universities Physics Alliance

Strathclyde (students and staff):

Team: Dino Jaroszynski, Salima Abu-Azoum, Maria-Pia Anania, Constantin

Aniculaesei, Rodolfo Bonifacio, Enrico Brunetti, Sijia Chen, Silvia Cipiccia, David

Clark, Bernhard Ersfeld, John Farmer, David Grant, Ranaul Islam, Riju Issac,

Yevgen Kravets, Tom McCanny, Grace Manahan, Adam Noble, Guarav Raj,

Richard Shanks, Anna Subiel, Xue Yang, Gregory Vieux, Gregor Welsh and Mark

Wiggins

Collaborators: Gordon Rob, Brian McNeil, Ken Ledingham and Paul McKenna

ALPHA-X: Current and past collaborators:

Lancaster U., Cockcroft Institute / STFC - ASTeC, STFC – RAL CLF, U. St. Andrews, U. Dundee, U. Abertay-Dundee, U. Glasgow, Imperial College, IST Lisbon, U. Paris-Sud - LPGP, Pulsar Physics, UTA, CAS Beijing, LBNL, FSU Jena, U. Stellenbosch, U. Oxford, LAL, PSI, U. Twente, TUE, U. Bochum, ....

ALPHA-X project

Current Support:

EPSRC, E.U. Laserlab, STFC, University of Strathclyde

consortium

Thank you