Strecher, compressor and time structure manipulation Xiangyu Zhou 20. Feb. 2015
Energy spread reduction using temporal manipulation Energy spread of 0.1% is required for SuperKEKB synchrotron injection. Gaussian Square 5nC 10nC 15nC 20nC 5nC electron Primary beam for positron production t When the charge distribution is uniform in a cylinder, the energy spread of the bunch is lower than the result of Gaussian charge distribution. For the laser source, the pulse width should be reshaped to rectangle structure.
Time structure of laser system Yb Oscilattor Stretcher Yb PCF Amplifier Yb:YAG thin-disk Amplifier SHG 100 fs 30 ps
Grating Pair Stretcher and Compressor Short Wavelength Long Wavelength γ θ Grating Phase Front Roof Mirror Compressor Negative GDD Roof Mirror Lens Z -f f Phase Front Stretcher Positive GDD
Grating pair Reflection Grating Transmission Grating 85% 95% Total Efficiency ~50% Total Efficiency ~80%
Spectral Range Adjustment For chirped pulse, the pulse shaping in the time domain can be controlled by adjusted the spectral shaping of the pulse. Spatial Masking Spatially dispersed d Chirp t t
Simulation
Pulse picker & Stretcher 4μm l/2 Stretcher WDM coupler LD Pump SMF 51.98 MHz 1740 gooves/mm Transmission grating > 90% loss Pulse spectrum after the stretcher
Pulse shaping Stretcher t t Pulse shaping by streak camera Telescope lens 1740-grooves/mm
1740-grooves/mm
Streak camera measurement at SHG stage FWHM: 30ps
CPA system Yb Oscilattor Yb Oscilattor Stretcher Stretcher Yb PCF Amplifier Yb PCF Amplifier Yb:YAG Thin-disk Amplifier Yb:YAG Thin-disk Amplifier SHG SHG Pulse Shaping Adjustment 100 fs 100 fs 30 ps 30 ps Yb Oscilattor Yb Oscilattor Yb:YAG Thin-disk Amplifier Yb:YAG Thin-disk Amplifier Compressor Stretcher Stretcher Yb PCF Amplifier Yb PCF Amplifier Compressor Pulse Shaping Adjustment SHG SHG Pulse Shaping Adjustment 30 ps 2 ns 2 ns 30 ps
Stretcher & Compressor FBG or Grating size is 18 cm for ns stretch
Vacuum Chamber
Slope injection at cathode Original pulse shaping 8mm 60° (Method-1) Grating 6.92mm 4mm 6mm(20ps) 9mm(30ps) (Method-2) Slit
Problem Without CPA With CPA Fiber amplifier limitation (mJns) Spectral range adjustment is difficult With CPA Structure of stretcher and compressor is huge Transmission efficiency Damage threshold of gratings