High Energy Electron Acceleration Using Plasmas, 6-10 June , Paris, 2005

1. Laser Electron AccelerationProject at JAERIMasaki KandoAdvanced Photon Research CenterJapan Atomic Energy Research Institute (JAERI) High Energy Electron Acceleration Using Plasmas, 6-10 June , Paris, 2005

2. Collaborators Yamazaki1,2), H. Kotaki1), S. Kondo1), T. Homma1), S. Kanazawa1), K. Nakajima1,3), L.M. Chen1), J. Ma1), H. Kiriyama1), Y. Akahane1), M. Mori1), Y. Hayashi1), Y. Nakai1), Y. Yamamoto1), K. Tsuji1), T. Shimomura1) , K. Yamakawa1) , J. Koga1), T. Hosokai4), Zhidkov4), K. Kinoshita4), M. Uesaka4), S. V. Bulanov1), T. Esirkepov1), M. Yamagiwa1), T. Kimura1), T. Tajima1) and International Experimental Taskforce (IET) members 1) APRC, JAERI 2) Kyoto University 3) High Energy Accelerator Research Organization (KEK) 4) The University of Tokyo

3. Table of Contents • Introduction • Theoretical work on Beam Quality • Our Approach to Good quality beams • High power laser :Bubble/Blow-out regime • Moderate power laser: Gas density control • Summary

4. Introduction JAERI Laser Electron Acceleration Project(2005-2009) • Demonstration of 1GeV Acceleration Bubble/blow-out, Fast-Z pinch capillary waveguide,.. • High quality beam production • Application - keV X-ray source (compact) We plan to use wakefield as an undulator - Pump-probe experiment (Ultrafast science)

5. Route to quasi-monoenergetic electrons J. Faure et al., Nature 431 (2004) S. Gordienko & A. Pukhov, Phys. Plasmas 12, 043109 (2005) • Bubble regime Blow-out regime Scaling laws • Length matching L=Ldp (L=n Ldp n:integer is ok?) Experiments W. Lu et al., This Workshop High peak power is required S. P. D. Mangles et al., Nature 431, 535 (2004) C. G. R. Geddes et al., Nature 431, 538 (2004) A. Yamazaki et al., submitted to PoP Not so high peak power is required E. Miura et al., J. Plasma Fusion Res. 81 255-260 (2005)

6. Energy spectrum of accelerated electrons 1D Hamiltonian, Motion in 1st wake-period S.V. Bulanov et al., appeared in Phys. Plasma, soon

7. Energy spectrum of fast electrons

8. Energy spectrum of fast electrons

9. Transverse emittance

10. Transverse emittance

11. Transverse emittance

12. Near-Term Experiment at JAERI Long-Focus experiment • Peak power > 50 TW • Pulse duration 23 fs • Focal length 775 mm / 450mm • Spot radius,w0 ~16µm / ~9 µm • Contrast 10-6 • Peak intensity 6.2x1018 W/cm2 a0=1.7 at 25TW 2.0x1019 W/cm2 a0=3.0 at 25TW • Plasma density 3x1018-1x1020 cm-3 • Target He-gas-jet • length 1.3-10 mm (slit length) Goal: Quasi-mono energetic electrons ‘Bubble /Blow-out regime’ Test of non-uniform plasma density Betatron X-ray measurement

13. Near-Term Experiment - Diagnosis magnet size 10cmx10cm • Electron • Charge Current Transformer • Energy Compact spectrometer w/Scintillating screen • High energy detection: Sampling calorimeter • Pulse duration • Bolometer (THz detection), Single-shot meas. by polychromator • Plasma • Channeling Schlieren/shadowgraphy/ Interferometry • X-ray • Energy Ross filter and Photon counting on CCD • Angular distribution Rail system & CCD and/or NaI

14. Experimental setup We are installing a new big target chamber OAP Test With He-Ne laser Almost perfect

15. 2D PIC Simulations Although 2D simulation underestimates the maximum energy when self-focusing happens, qualitative estimation is valid. Uniform plasma a0=1.7 T=23 fs, sx=16µm Ne=3x1018 cm-3 Ne=1.7x1019 cm-3

16. 2D PIC Simulations Parabolic- realistic distribution Sharp-density transition a0=1.7 T=23 fs, sx=16µm Ne=1.7x1019 cm-3 Ne=1.7x1019 - 8.5x1018cm-3 Narrow

17. Schedule 2005 4 5 6 7 8 9 10 11 12 Laser maintenance Target Chamber Experiment Oscillator replacement/ Regen realignment Power Amp. YAG replacement New big chamber installation Optics adjustment Spot, Pulse duration check Shots (Electron/Ion)

18. Sharp density transition enhances injection S. V. Bulanov et al., Phys.Rev.E 58, R5257 (1998) H. Suk et al., Phys. Rev. Lett 8, 1011 (2001) T. Hosokai et al., Phys. Rev. E 67, 036407 (2003) P. Tomassini et al., Phys. Rev. ST 6, 121301 (2003) No energetic electrons in homogenous plasma Quasi-monoenergetic structure is formed if the length is appropriate. a0=1.3 t=17fs L=2µm 2.1x1019 cm-3 1.1x1019 cm-3 ne P. Tomassini et al., Phys. Rev. ST 6, 121301 (2003)

19. U. Tokyo Artificial prepulse & High contrast Demonstration has been done Next step: controllability & stability Artificial prepulse In the compressor chamber, we will install optics to produce prepulse Uncompressed Laser Main pulse ~ 40 fs Artificial prepulse, ~ns High Contrast(better than 10-7) •Fast Pockels Cell •Frequency doubling Hydrodynamic code T. Hosokai et al., PRE 2003

20. Control of gas-jet density • Compression by shock-waves Controlling a curvature of the wall makes it possible L~100 µm ~ spatial resolution Better measurement and Wall shape optimization are required

21. Preliminary test with density control In case of short-focal length, the up-ramp region destroys laser focusing To avoid ‘up-ramp’ density profile Solution1 : Gas-Cell + Supersonic gas-jet Exit aperture Small aperture Lavar type Wall shape M. Uesaka Lab. U. Tokyo This configuration will be tested Solution2 Use longer focal length

22. Summary • Theoretical investigation of energy distribution is performed, and qualitatively reproduce experimental data. • Parameter survey will be done around ‘Bubble / Blow-out regime/’ with JAERI 100 TW, 23 fs laser. • Laser and target chamber improvement is under way. • Control of gas-distribution and prepulse are important for electron acceleration. • We are developing Gas-jet-nozzle in order to control particle injection and acceleration for relatively small lasers.