1. 1 High Energy Electron Acceleration Using Plasmas, 6-10 June, Paris, 2005 Laser Electron Acceleration Project at JAERI Masaki Kando Advanced Photon Research Center Japan Atomic Energy Research Institute (JAERI)

2. 2 Collaborators A. Yamazaki 1,2), H. Kotaki 1), S. Kondo 1), T. Homma 1), S. Kanazawa 1), K. Nakajima 1,3), L.M. Chen 1), J. Ma 1), H. Kiriyama 1), Y. Akahane 1), M. Mori 1), Y. Hayashi 1), Y. Nakai 1), Y. Yamamoto 1), K. Tsuji 1), T. Shimomura 1), K. Yamakawa 1), J. Koga 1), T. Hosokai 4), A. Zhidkov 4), K. Kinoshita 4), M. Uesaka 4), S. V. Bulanov 1), T. Esirkepov 1), M. Yamagiwa 1), T. Kimura 1), T. Tajima 1) 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. 3 Table of Contents 1. Introduction 2. Theoretical work on Beam Quality 3. Our Approach to Good quality beams 1. High power laser :Bubble/Blow-out regime 2. Moderate power laser: Gas density control 4. Summary

4. 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. 5 Route to quasi-monoenergetic electrons Bubble regime Blow-out regime Scaling laws Length matching L=Ldp (L=n Ldp n:integer is ok?) E. Miura et al., J. Plasma Fusion Res. 81 255-260 (2005) Experiments S. P. D. Mangles et al., Nature 431, 535 (2004) C. G. R. Geddes et al., Nature 431, 538 (2004) W. Lu et al., This Workshop High peak power is required Not so high peak power is required A. Yamazaki et al., submitted to PoP J. Faure et al., Nature 431 (2004) S. Gordienko & A. Pukhov, Phys. Plasmas 12, 043109 (2005)

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

7. 7 Energy spectrum of fast electrons

8. 8

9. 9 Transverse emittance

10. 10 Transverse emittance

11. 11 Transverse emittance

12. 12 Near-Term Experiment at JAERI Peak power > 50 TW Pulse duration 23 fs Focal length775 mm / 450mm Spot radius,w 0 ~16 µ m / ~9 µ m Contrast10 -6 Peak intensity6.2x10 18 W/cm 2 a 0 =1.7 at 25TW 2.0x10 19 W/cm 2 a 0 =3.0 at 25TW Plasma density3x10 18 -1x10 20 cm -3 TargetHe-gas-jet length1.3-10 mm (slit length) Long-Focus experiment Goal: Quasi-mono energetic electrons ‘ Bubble /Blow-out regime ’ Test of non-uniform plasma density Betatron X-ray measurement

13. 13 Near-Term Experiment - Diagnosis Electron –ChargeCurrent 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 –EnergyRoss filter and Photon counting on CCD –Angular distributionRail system & CCD and/or NaI magnet size 10cmx10cm

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

15. 15 2D PIC Simulations Although 2D simulation underestimates the maximum energy when self-focusing happens, qualitative estimation is valid. Ne=3x10 18 cm -3 Ne=1.7x10 19 cm -3 Uniform plasma a 0 =1.7 T=23 fs, sx=16 µ m

16. 16 2D PIC Simulations Ne=1.7x10 19 - 8.5x10 18 cm -3 Ne=1.7x10 19 cm -3 Sharp-density transition Parabolic- realistic distribution a 0 =1.7 T=23 fs, sx=16 µ m Narrow

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

18. 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) 2.1x10 19 cm -3 1.1x10 19 cm -3 L=2 µ m P. Tomassini et al., Phys. Rev. ST 6, 121301 (2003) No energetic electrons in homogenous plasma a 0 =1.3  =17fs nene Quasi-monoenergetic structure is formed if the length is appropriate.

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

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

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

22. 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.