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Ultra-stable flashlamp-pumped laser

Ultra-stable flashlamp-pumped laser. A.Brachmann, J.Clendenin, T.Galetto, T.Maruyama, J.Sodja, J.Turner, M.Woods. Outline. Introduction Laser System Setup Recent Modifications Experimental Results Conclusions and Summary. Introduction. SLAC built Flashlamp-pumped Ti:Sapphire laser system

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Ultra-stable flashlamp-pumped laser

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  1. Ultra-stable flashlamp-pumped laser A.Brachmann, J.Clendenin, T.Galetto, T.Maruyama, J.Sodja, J.Turner, M.Woods

  2. Outline • Introduction • Laser System Setup • Recent Modifications • Experimental Results • Conclusions and Summary

  3. Introduction • SLAC built Flashlamp-pumped Ti:Sapphire laser system • Installation in 1993 at the SLAC PES • Generation of polarized electrons in combination with SLAC’s Polarized Electron Gun • Recent Modifications result in increased stability and output power

  4. Benefit of low jitter • Statistics of experiments • Reduce Beam loading • Reduction of residual • dispersion and • wakefields • Facilitates beam tuning • and minimizes losses Time needed to achieve 100 ppb for E-158 assymmetry statistics (for 120 Hz rep. Rate) (assumption that laser is only source of jitter)

  5. Laser System Setup Cavity flashlamps Spectrometer CCD ‘SLICE’ Photodiode Brewster /2 Ti:Sapphire HBS F=500mm F=750mm ‘TOPS’ -PC ‘SLICE’ -PC PL /2 PL PL PL: Polarizer PC: Pockels cell ‘LONGPULSE’ Photodiode

  6. Laser system periphery • SLAC built pulsed power supply • SLAC built cooling water system (closed loop > 16 M) • Commercial Pockels cell driver • SLAC built HV power supply and control of TOPS Pockels cell • Variety of Controls & Diagnostics integrated into control system • (Power supply, Pockels cell HV, Photodiodes, Spectrometer, CCD)

  7. Parameters of operation

  8. Temporal pulse profile and timing setup

  9. Recent modifications • Cavity optimization according to thermal lensing included in resonator modelling results • Elimination of cavity halfwave plate reduces element sensitive to optical damage • Wavelength change to 805 nm required by new photocathode yields higher output power  Operation near gain maximum for Ti:Sapphire material

  10. Thermal lensing

  11. wx w0 x Rx Cavity simulations Thermal lens flat 2 mcc 5 mcc L1 L2

  12. Spotsize within gain medium as a function of thermal lens and mirror spacing

  13. Wavefront radius of curvature as a function of thermal lens and mirror spacing

  14. (500 data points) Slice J (Photodiode) TORO 488 TMIT MEAN 41.35 3.95E+11 Jitter [%] 0.54 0.46 Laser stability and e- beam stability near target are highly correlated

  15. Optical damage on cavity halfwave plate surfaces (damaged coating)

  16. Controlled crystallographic orientation of laser rod

  17. HV [kV] Jitter [%] 7.6 0.094 7.7 0.059 7.8 0.149 7.9 0.205 8.0 0.212 8.1 0.215 Power supply stability as a function of high voltage level

  18. Conclusions and Summary • Stable operation of laser systems required for polarized e-beams is achieved • ‘Home built’ systems preferred over commercial systems • greater flexibility • better support • straightforward integration into existing control system • Development laboratory with duplicate system is essential if continuous production is required

  19. References • Humensky et al.; SLAC’s Polarized Electron Source Laser System and Minimization of Electron Beam Helicity Correlations for the E-158 Parity Violation Experiment; NIM; to be published • Brachmann et al.; SLAC’s Polarized Electron Source Laser System for the E-158 parity violation experiment; Proceedings of SPIE, Volume 4632, 211-222, 2002

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