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M. Hosaka a , M. Katoh b , C. Szwaj c , H. Zen b M. Adachi b , S. Bielawski c , C. Evain c

M. Hosaka a , M. Katoh b , C. Szwaj c , H. Zen b M. Adachi b , S. Bielawski c , C. Evain c M. Le Parquier c , Y. Takashima a ,Y. Tanikawa b Y. Taira b , N. Yamamoto a a Synchrotron Radiation Research Center, Nagoya University (Japan)

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M. Hosaka a , M. Katoh b , C. Szwaj c , H. Zen b M. Adachi b , S. Bielawski c , C. Evain c

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  1. M. Hosakaa, M. Katohb, C. Szwajc, H. Zenb M. Adachib, S. Bielawskic, C. Evainc M. Le Parquierc, Y. Takashimaa ,Y. Tanikawab Y. Tairab, N. Yamamotoa aSynchrotron Radiation Research Center, Nagoya University (Japan) bUVSOR Facility, Institute for Molecular Sciences, Okazaki (Japan) cLab PhLAM,Université de Lille (France) * Intense coherent THz synchrotron radiation induced by a storage ring FEL seeded with a femtosecond laser

  2. Contents • Laser bunch slicing and coherent synchrotron radiation (CSR) Example: UVSOR experiment: • Storage ring FEL • Seeded storage ring FEL experiment • Summary

  3. Laser Bunch Slicing and Coherent Synchrotron Radiation (CSR) • Injection of short pulse high power laser (100 fsec, 10 GW). • FEL interaction between the laser and electron beam inside undulator. Storage ring BESSY, ALS, UVSOR-II etc.

  4. Laser Bunch Slicing and CSR (Cont.) After bending magnet(s) △z=R56△e/E Phase space Projection to horizontal (temporal) axis • Local energy modulation is created. • After bending magnet, it is converted to density modulation • (time of flight dispersion). • CSR is generated due to the micro-structure.

  5. Laser Bunch Slicing and CSR (Cont.) M. Shimada et al. JJAP 46 (2007) 7939 Power radiated by N electrons =N2 x Power radiated by 1 electron Spectrum ~ Fourier transform of r(z)

  6. Narrow-band CSR (@UVSOR-II) S. Bielawski et al. Nature Physics, 4, 390–393 (2008)

  7. Narrow-band Coherent Synchrotron Radiation :Measured spectra “Tunable” “Narrow Band” CSR” Application of narrow band CSR: H. Zen et al. TUPA 14

  8. CSR using a storage ring FEL (an internal laser) instead of an external short pulse laser. Why SR-FEL? Optical klystron Laser pulse Mirror Mirror Electron bunch Storage ring FEL • Storage ring FEL repetition rate is ~ 10 MHz ! • Ordinal CSR (or Bunch slice): repetition rate is limited by laser repetition ( ~ 1 kHz or less) • Using SR-FEL, CSR with much higher repetition rate is expected.

  9. Why Q-switch SR-FEL ? • In storage ring, there are two types of lasing, CW lasing and repetitive Q-switch lasing . • In Q-switch mode, rf modulation technique is used and a higher peak power is available. Fast time Streak camera image of temporal structure of FEL Slow time • In stable CW lasing, the laser pulse width is determined by an equilibrium condition. • Short pulse lasing is difficult

  10. Why Q-switch SR-FEL ? • In Q-switch lasing, the lasing starts from noise. • If short pulse laser is injected to Q-switch FEL as seed, short pulse lasing is expected. • Long sustain high repetition rate CSR (or bunch slice) is expected. Short pulse FEL lasing Injection short pulse laser

  11. Experimental setup l = 400 nm SHG Helical optical klystron Infra-red Beamline UVSOR-IIstorage ring Ti: Sa mode lock laser: 800 nm 2mJ InSb:Bolometer Laser : Second harmonics of Ti:Sa laser : Pulse width: 300 fsec –FWHM or ~ 100 psec-FWHM Undulator: Helical optical klystron 400 nm C. Szwaj TUPB05 H. Zen WEPA17

  12. Experimental result (streak camera) 100 psec 700 psec 700 psec Femto-sec injection NO injection 5 msec 5 msec Streak Camera Image • Short pulse lasing • (Shorter than s.c. resolution) • Faster rise time • Intensity is not so changed. FEL intensity

  13. Experimental result (CSR) CSR intensity increases 50 times (as compared the case no injection)

  14. Experimental result ( FEL& CSR ) • Simultaneous measurement of CSR and FEL • CSR is produced in early stage of the lasing

  15. Simple phase space simulation(1) Fresh Electron Energy Projection Phase 0.7 times of Synchrotron oscillation: Laser field is weak.

  16. Simple phase space simulation (2) Energy Fresh Electron Phase 1.5 times of Synchrotron oscillation : Laser field is strong

  17. Simple phase space simulation (3) No Fresh Electron Energy Phase 3.5 times of Synchrotron oscillation Laser field is strong

  18. Simple phase space simulation (4) Simulation almost reproduces the experimental result. Detailed calculation is in progress.

  19. Summary • Succeeded in Q-switch FEL lasing seeded by femto-sec laser • Intense CSR production is observed • Simple simulation is made, detailed simulation is in progress. • Future Applications: • Bunch slice to produce short pulse SR • Injection of the amplitude modulated laser to produce narrow band CSR

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