Strategies for Future Laser Plasma Accelerators J. Faure, Y. Glinec, A. Lifschitz, A. Norlin, C. Rechatin, & V.Malka Laboratoire d’Optique Appliquée ENSTA-Ecole Polytechnique, CNRS Palaiseau, FRANCE LOA Partially supported by CARE/PHIN FP6 project

Summary Part 1 : Laser plasma accelerator : motivation Part 2 : Laser plasma accelerator as booster Part 3 : Laser Plasma accelerator as injector : Production of monoenergetic electron beam Part 4 : New scheme of injection : toward a stable, tuneable and quasi monoenergetic electron beam. Part 5 : Applications Part 6 :Conclusion and perspectives LOA

Plasma cavity 100  m 1 m RF cavity Courtesy of W. Mori & L. da Silva E-field max ≈ few 10 MeV /meter (Breakdown) R>R min Synchrotron radiation Classical accelerator limitations

Tajima&Dawson, PRL79 How to excite Relativistic Plasma waves ?  laser ≈ T p / 2 = >Short laser pulse Laser pulse F≈-grad I Electron density perturbation Phase velocity v  epw =v g laser => close to c Analogy with a boat The laser wake field ez nE~ Are Relativistic Plasma waves efficient ? E z = 0.3 GV/m for 1 % Density Perturbation at cc -1 E z = 300 GV/m for 100 % Density Perturbation at cc -1 Tajima and Dawson, PRL (1979) LOA

Interaction and dephasing lenghts L acc. =  Z R Diffraction limited  W diff. [MeV]  580 ( / p )/(1+a 0 2 /2) 1/2 P [TW]  W ch [MeV]  60 ( p /w 0 ) P [TW] L acc Guiding : channel or relativistic W. P. Leemans et al., IEEE 24, 2 (1996) electron t 1 t 2 t 3 e   >>  >> 1=> L deph. =(=( 0 /2)(n c /n e ) 3/2 L Deph. = p   2 LOA

Summary Part 1 : Laser plasma accelerator : motivation Part 2 : Laser plasma accelerator as booster : Part 3: Laser Plasma accelerator as injector : Production of monoenergetic electron beam Part 4 : New scheme of injection : toward a stable, tuneable and quasi monoenergetic electron beam. Part 5 : Applications Part 6 :Conclusion and perspectives LOA

Small Laser amplitude a 0 =0.5 Homogeneous plasma Accelerating & focusing fields in Linear RPW Electron density Pulse Defocusing EzEz ErEr Focusing Accelerating Decelerating LOA

Small Laser amplitude a 0 =0.5 Parabolic plasma channel Accelerating & focusing fields in plasma channel Electron density Pulse Focusing Defocusing Accelerating Decelerating Pulse EzEz ErEr LOA

Focusing Defocusing Accelerating Decelerating Large Laser amplitude a 0 =2 Homogeneous plasma Accelerating & focusing fields in NL RPW Electron density Pulse relativistic shift of  p LOA

Three Injection schemes Before the pulse Low energy laser Low energy => Low charge High Energy => Short Bunch LOA

 bunch = 200 fs LOA

Injecting the LOA  bunch = 30 fs, 170 MeV LOA

E=9 J P= 0.15 PW a 0 =1.5 Parabolic channel: r 0 =47  m, n(r)=n 0 ( r/r 0 ) n 0 = 1.1×10 17 cm -3 3 GeV, 1% energy spread e-beam 3.5 GeV, with a relative energy spread FWHM of 1% and an unnormalized emittance of mm. LOA

Summary Part 1 : Laser plasma accelerator : motivation Part 2 : Laser plasma accelerator as booster : Part 3: Laser Plasma accelerator as injector : Production of monoenergetic electron beam Part 4 : New scheme of injection : toward a stable, tuneable and quasi monoenergetic electron beam. Part 5 : Applications Part 6 :Conclusion and perspectives LOA

Laser plasma injector Scheme of principle Experimental set up LOA

Charge in the peak : pC Energy distribution improvements: The Bubble regime PIC Experiment Divergence = 6 mrad At LOA J. Faure et al. Nature (2004) LOA

Quasi-monoenergetic beams reported in the litterature Name Article Lab EnergydE/EChargeNe Intensity  L /T p Remark [MeV][%] [pC] ManglesNature (2004)RAL ,51,6 GeddesNature (2004)L'OASIS ,2Channel FaureNature (2004)LOA ,7 HiddingPRL (2006)JETI4790, ,6 HsiehPRL (2006)IAMS ,6 HosokaiPRE (2006)U. Tokyo11, ,0Preplasma MiuraAPL (2005)AIST720432E ,1 HafzPRE (2006)KERI4, ,4 MoriArXiv (2006)JAERI20240,8500,94,5 ManglesPRL (2006)Lund LC ,4 [x10 18 /cm 3 ][x10 18 W/cm 2 ] Several groups have obtained quasi monoenergetic e beam but at higher density (  L >  p ) LOA

310-μm-diameter channel capillary P = 40 TW density 4.3×10 18 cm −3. GeV electron beams from a « centimetre-scale » accelerator Leemans et al., Nature Physics, september 2006 LOA

After 5 Z r / 7.5 mm Energy (MeV) f(E) (a.u.) w 0  20  m  30fs a 0  4  0.8  m P  200TW n p  1.5 × cm  3 Courtesy of UCLA& Golp groups Laser plasma injector : GeV electron beams LOA

Laser plasma injector : + good efficiency : E e-beam /E laser  10 % + simple device + with channel : GeV range is obtained 1 with moderate laser power * But since the efficiency is conserved a compromise between charge and energy must be found -Stability has been recently improved ! - Energy spread still too large for some applications :  E/E  few % LOA

Summary Part 1 : Laser plasma accelerator : motivation Part 2 : Laser plasma accelerator as booster : Part 3: Laser Plasma accelerator as injector : Production of monoenergetic electron beam Part 4 : New scheme of injection : toward a stable, tuneable and quasi monoenergetic electron beam. Part 5 : Applications Part 6 :Conclusion and perspectives LOA

Controlling the injection E. Esarey et al, PRL 79, 2682 (1997), G. Fubiani et al. (PRE 2004) Counter-propagating geometry: pump injection Plasma wave Principle: Pump beam Injection beam Ponderomotive force of beatwave: F p ~ 2a 0 a 1 /λ 0 (a 0 et a 1 can be “weak”) y Boost electrons locally and injects them: y INJECTION IS LOCAL IN FIRST BUCKET y electrons LOA

Colliding pulse injection scheme: mechanism Plasma wave Electron motion Beatwave Buckets at 0 /2  p z =2mc(a 0 a 1 ) 1/2 Buckets at l p

Experimental set-up Injection beam Pump beam Probe beam LANEX B Field 250 mJ, 30 fs  fwhm =30 µm I ~ 4×10 17 W/cm 2 a 1 = mJ, 30 fs,  fwhm =16 µm I ~ 3×10 18 W/cm 2 a 0 =1.2 electron spectrometer to shadowgraphy diagnostic Gas jet LOA

Aligning the beams with shadowgraphy LOA

PUMP BEAM INJECTION BEAM Synchronizing the beams with shadowgraphy pumpinjection Probe beam LOA

From self-injection to external injection n e =1.25×10 19 cm -3 n e =10 19 cm -3 n e =7.5 × cm -3 pump Single beam pump injection 2 beams Self-injection Threshold n e =7.5 × cm -3 LOA

Laser stability Pump pulse: I=3.4× /- 0.2×10 18 W/cm 2 (RMS=5.5 %) Injection pulse: I=4.4× /- 0.27×10 17 W/cm 2 (RMS=6.1 %) To camera 90° angle prisme LOA

Stability of laser beam pointing Worse case Dx=10 µm Injection beam Pump beam RMS case Dx=5 µm LOA

Optical injection by colliding pulses leads to stable monoenergetic beams STATISTICS value and standard deviation *Charge measurements with absolute calibration of Lanex film (ICT gave a factor of 8 higher charge) LOA Bunch charge= 19 +/- 6 pC Peak energy= 117 +/- 7 MeV DE= 13 +/- 2.5 MeV DE/E= 11 % +/- 2 % Divergence= 5.7 +/- 2 mrad Pointing stability= 2 mrad

Monoenergetic bunch appears when Lasers are overlapped LOA

Parallel polarization Crossed polarization Monoenergetic bunch comes from colliding pulses: polarization test LOA

Controlling the bunch energy by controlling the acceleration length By changing delay between pulses: Change collision point Change effective acceleration length Tune bunch energy Pump beam Injection beam Gas jet 2 mm LOA

Tunable monoenergetic bunches pump injection pump injection late injection early injection pump injection middle injection Z inj =225 μm Z inj =125 μm Z inj =25 μm Z inj =-75 μm Z inj =-175 μm Z inj =-275 μm Z inj =-375 μm LOA J. Faure et al., Nature 2006

Tunable monoenergetic electrons bunches: 190 MeV gain in 700 µm: E=270 GV/m Compare with E max =mc  p /e=250 GV/m at n e =7.5×10 18 cm -3 LOA

Part 1 : Laser plasma accelerator : motivation Part 2 : Laser plasma accelerator as booster Part 3 : Laser Plasma accelerator as injector : Production of monoenergetic electron beam Part 4 : New scheme of injection : toward a stable, tuneable and quasi monoenergetic electron beam. Part 5 : Applications Part 6 :Conclusion and perspectives Summary LOA

In collaboration with CEA / DAM Material science:  -ray radiography High resolution radiography of dense object with a low divergence, point-like electron source Glinec et al., PRL (2005) LOA

 -radiography results 20mm Cut of the object in 3D Spherical hollow object in tungsten with sinusoidal structures etched on the inner part. Measured Calculated Source size estimation : 450 um Glinec et al., PRL (2005) LOA

Particle beam in medicine : Radiotherapy 99% Radiotherapy with X ray LOA

Radiation Therapy : context Depth in tissue Photon dose Photon beams are commonly used for radiation therapy tumor Photon beam Dose LOA

Medical application : Radiotherapy VHE ELECTRONS LOA

VHE Radiation Therapy Depth in tissue VHE dose l Reduced dose in save cells l Deep traitement l Good lateral contrast tumor VHE Dose LOA

Monte Carlo simulation of the dose deposition in water Electron gun : quasi-monoenergetic (170MeV) with 0.5nC and 10mrad divergence Water target : 40cm x 4cm x 4cm divided in 100 pixels in all directions. Simulation parameters : CutRange=100um and N 0 =10 5 electrons In collaboration with DKFZ LOA

Dose deposition profile in water Glinec et al., Med. Phys. 33, 1 (2006) O.P. LOA

Fudamental aspect : fs radiolysis H 2 O (e - s, OH., H 2 O 2, H 3 O +, H 2, H. ) e-e- Very important for: Biology Ionising radiations effects B. Brozek-Pluska et al., Radiation and Chemistry, 72, (2005) **Ar. LOA

Compact XFEL: towards a bright X ray source Applications: study of complex structures (X-ray diffraction, EXAFS) But ps time scale <ps  ~  rad 10cm LOA Reduction of accelerator Reduction of the undulator

Conclusions / perspectives SUMMARY Optical injection by colliding pulse: it works ! Monoenergetic beams trapped in first bucket Enhances dramatically stability Energy is tunable: MeV Charge up to 80 pC in monoenergetic bunch  E/E down to 5 % (spectrometer resolution),  E ~ MeV Duration shorter than 10 fs. PERSPECTIVES Q Combine with waveguide: tunable up to few GeV’s with  E/E ~ 1 % Design future accelerators Model the problem for further optimization: higher charge Stable source: extremely important accelerator development (laser based accelerator design) light source development for XFEL applications (chemistry, radiotherapy, material science) LOA