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Characteristics of quasi-monoenergetic electron beam produced by 3 TW, 70 fs laser

The 12th Advanced Accelerator Workshop July 10-15, 2006, Lake Geneva. 2006.7.11. Characteristics of quasi-monoenergetic electron beam produced by 3 TW, 70 fs laser. Masaki Kando Advanced Photon Research Center (APR) Quantum Beam Science Directorate (QuBS) Japan Atomic Energy Agency (JAEA).

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Characteristics of quasi-monoenergetic electron beam produced by 3 TW, 70 fs laser

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  1. The 12th Advanced Accelerator Workshop July 10-15, 2006, Lake Geneva 2006.7.11 Characteristics of quasi-monoenergeticelectron beam produced by 3 TW, 70 fs laser Masaki Kando Advanced Photon Research Center (APR) Quantum Beam Science Directorate (QuBS) Japan Atomic Energy Agency (JAEA)

  2. Collaborators JAEA M. Mori, I. Daito, Y. Hayashi, L. M. Chen, K. Ogura, H. Kotaki, A. Pirozhkov, J. Ma, Y. Fukuda, A. Sagisaka, T. Zh. Esirkepov, A. Yamazaki, S. Kondo, T. Homma, K. Nakajima, H. Daido, S. V. Bulanov, T. Kimura Univ. of Tokyo T. Hosokai, K. Kinoshita, A. Zhidkov, M. Uesaka

  3. Table of Contents • Introduction • Laser Wakefield Acceleration(skip) • Previous results(skip) • Laser system at JAEA • Recent Experimental Results • Quasi-monoenergetic electron generation • Repeatability • Comparison with simulations • Ongoing Experiments • Summary

  4. JLITE-X laser system JLITE-X (abbreviation) = JAEA Laser system for Laser-matter InteracTion Experiment Output Energy: >200 mJ (on target) Pulse Width: <70 fs (FWHM) Peak Power: >3 TW Repetition Rate: 10Hz • Optimized to reduce ASE (10-5) • Pointing stabilizer < ± 10 µrad • Single-shot operation

  5. Experimental setup f/13 f=650mm OAP Laser parameter: Pulse duration: 70 fs Laser energy: 210 mJ Spot diameter: 25µm(1/e2) (Concentration: 55% ) Laser intensity in vacuum: 4x1017 (Averaged ) 8x1017 W/cm2(Peak) Rayleigh length: 400 um Probe beam 3TW laser beam Colliamator slit E-beam Electromagnet Target: He gasjet (super sonic gasjet): 1.2mm x 10 mm nozzle Scale length of the gasjet: 600 um Measurement: Electron spectrum Laser propagation with probe beam

  6. Typical image of the Quasi-monoenergetic electron beam Electron density: 4.7x1019 cm-3 deconvolution Typical energy resolved e-beam image (Image was taken by using IP) Energy distribution of the electron beam Energy: ～20(19.6)MeV Energy Spread: 4.0 MeV Electron Yield: 0.8 pC (Max. ~ 8 pC) Divergence : 4.6 mrad

  7. Emittance estimation • Electron Beam emittance ε • Normalized EmittanceεN Normalized emittance eN= 0.7 p mm mrad e=s1 (s22-s12) /L ～ s1s2 / L eN = e g b s1 : beam size (rms) at generation point (= 12.5 um /2 supposed as a laser spot diameter) s2: beam size (rms) at any observation point (= 4.5 mm /2 ) L: Distance between generation point (= 757.5 mm)

  8. Energy distribution changes as a function of the plasma density Strongly Modulated Broaden (peak energy is held) peak energy is increased (peak energy is 20 MeV) Quasi-Mono (peak energy is 8.5 MeV) Fine tuning of the plasma density can control the peak energy of electron beams. Now, we are measuring this feature on detail.

  9. Single-shot measurement withPhosphor screen and ICCD Camera Spatial profile measurement of electron beams Due to peak intensity was saturated 8.4 mrad (horizontal) x 6.4 mrad (vertical) <6.4 mrad 10 mrad <8.4 mrad

  10. Reproducibility of QME Results of a sequence of 66 shots Note that we DO NOT choose suitable shots! Ne=4.7x1019cm-3 Divergence Energy

  11. Reproducibility of QME (cont’d) Example In a sequence of 66shots Type of Energy Distribution No.of shots Quasi-Mono (peak) 25 (38%) Quasi-Mono (Not clear peak) 12 (18%) Maxwellian 27 (41%) Undetectable 2 (3%) Peak energy 6-20.8 MeV (avg. 11 MeV), 20-48%

  12. 2D-PIC simulation of SMWFA Regime Position of the Laser Pulse Front Ez Ni “snake” in the ion density

  13. simulations experiment Energy vs. Plasma density a) b) Electron energy spectrum versus plasma densitya) Experimental data and b) Simulation results1. ne = 4.1 × 1019cm−3; 2. ne = 4.7 × 1019cm−3; 3. ne = 5× 1019cm−3;4. ne = 6.6× 1019cm−3. The 2D-PIC simulation reproduces experimentally obtained data.

  14. Present Experimental Setup Plasma diagnosis (shadowgraph,interferometry) Probe pulse (100fs, 820nm) Transmitted Source Monitor (spectrum, spot) Driver Laser (200mJ, 70fs, 820nm) UV-VIS Spectrometer Electron Spectrometer X-ray Pinhole Camera Grazing Incidence Spectrometer (X-ray CCD) Source Pulse (4-10mJ, 100fs, 820nm)

  15. Ongoing Experiments • Proof-of-principle of Flying Mirror Concepts • S. V. Bulanov et al., Phys. Rev. Lett. 91, 085001 (2003) • Optical Injection using Colliding scheme • E. Esarey et al., Phy. Rev. Lett. 79, 2682 (1997) • H. Kotaki et al., Phys. Plasmas 11, 3296 (2004) • Thomson scattering X-ray generation • H. Schwoerer et al., Phys. Rev. Lett. 96, 014802 (2006) • In particular, measure evolution of electron energy • THz radiation from Solitons • T. Zh. Esirkepov et al., JETP Lett. 68, 36 (1998); PRL 92, 255001 (2004)

  16. Summary • Collimated, 20MeV quasi-monoenergetic electron beam have been produced with a relatively small laser and a low vacuum intensity. • 2D-PIC results explain well the experimental results. • Next step: Improve stability

  17. Single-shot, Online ESM Example of QME data Repeatable production of QME!

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