Development of Photocathode RF Gun No.

Development of Photocathode RF Gun No. - Development of Multi Pulse Laser System - Ryunosuke Kuroda Research Institute for Science and Engineering, Waseda University, Japan

Outline Introduction Our Purpose 357MHz Seed Laser system Layout Performance Laser Amplifier system & Harmonic generation Layout Timing jitter and Amplitude jitter measurement technique Time domain demodulation technique Preliminary Experiments using 119MHz Seed Laser Future Schedule

Purpose Multi Bunch Electron Beam Generation using Cs2Te Photo-cathode RF-gun Requirements for Multi Bunch Beam Bunch Charge Bunch Length Bunch to Bunch Spacing Number of Bunches Quantum Efficiency >1 nc/bunch <10 ps(fwhm) 2.8 ns 1-20 bunches >1% (Cs2Te) Laser Energy Laser Pulse Width Pulse to Pulse Spacing >310 nj/pulse @266nm <10 ps(fwhm) 2.8 ns (357MHz Seed Laser) Very Stable Multi Pulse Laser System Research Institute for Science and Eengineering, Waseda University

Components of Multi Pulse Laser System Seed Laser Amplifier System Pulse Slicer Pulse Shape Controller Harmonic Generator 357 MHz Nd:YVO4 Laser (Time-Bandwidth) 4 x Nd:YAG rods (Flash Lamp Pumping) (HOYA) Pockles cell (rise & fall time about 3ns) Pockles cell (rise time about 1us) 2 x BBO Crystal New Clean Room @KEK-ATF Security Test to get a permission to use the Seed laser system have been performed only 2 weeks ago. We don t have enough data. So, We will explain our system easily.

Seed Laser System (Nd( Nd:YVO4) Laser Medium Laser Wave Length Pulse Width (FWHM) Average Laser Power Repetition Rate Nd:YVO4 1064 nm 7 ps 400 mw 357 MHz Timing stabilizer

Inside of The Seed Laser System (Nd:YVO4) Nd:YVO4 LD SESAM AMP PD

Timing Stabilized System using PLL (Phase Locked Loop) LD pump Nd:YVO4 Reference 357 MHz PZT(SESAM) AMP Photo diode Timing Stab.

357MHz Seed Laser 0.4 2.8 ns 0.35 Amplitude [V] 0.3 0.25 0.2 0.15 0.1 SESAM Reflective Mirror with 0.05 0 0 2 4 6 8 10 Time [ns] PD Signal Saturable absorber

Seed Laser Profile Laser Diameter (FWHM) Horizontal : 0.984 mm Vertical : 0.987 mm 60cm behind

Laser Amplifier System Seed Laser BBO 4 x Flash lamp pumped Nd:YAG rods This Laser Amplifier System was used at JNC. Moved from JNC to KEK (April) We have improved the used Laser Amplifier System to apply the 357 MHz Seed Laser

Scheme of The Laser System Macro pulse repetition rate 6.25 Hz Seed Laser 357 MHz Nd:YVO4 400mW 1.12 nj/pulse 7ps 1064 nm Pulse Slicer 1-20 pulses/ macro pulse Envelope shaping Pockels cell Feed back PD AMP1 AMP2 AMP3 AMP4 2-pass 1-pass 1-pass 1-pass Flash lamp pumped Amplifier Nd:YAG rods >2 x 10^4 gain SHG 532 nm 266 nm FHG BBO Crystal BBO Crystal (1w 4w ~5%) 1.2 uj/pulse, 266nm 1-20 pulses (2.8 ns spacing)

Jitter Measurements using Time Domain Demodulation Technique Seed Laser Signal Vre BPF φ ( t ) = 1 n tan 1 V V im re FFT n-th harmonics Vim V n = vn[ 1+ε ( t)]sin[ n{2 πfrt + φ( t)}] = V re sin( 2π frt) + V im ε( t) = cos(2πf r V t) re 2 + V v n im 2 V V re im v n (PSD) Sφ( f ) Sε( f ) = vn[ 1+ ε( t)]cosnφ( t) = vn[ 1+ ε( t)]sin nφ( t)

Preliminary Experiments using 119MHz Seed Laser Laser Medium Pulse Width (FWHM): Laser Wavelength Average Laser Power Repetition Rate Nd:YLF 10 ps 1047 nm 200 mw 119MHz Timing stabilizer This experiment is measuring the jitter and the dependence on RF(2856MHz). (N = 10)

σ Timing Jitter Measurement TJ = 1 2πf r f f high low S φ ( f ) df Phase Noise PSD [rad 2 /Hz] rms Timing JItter Reference 119 MHz 0.26 ps RF ON 0.26 ps RF OFF 0.25 ps 10-4 10-6 10-8 10-10 10-12 10-14 Reference 119 MHz Stab.ON / RF OFF Stab.ON / RF ON 0.01 0.1 1 10 100 1000 10 4 10 5 10 6 Frequency [Hz] Phase Noise PSD Integral range : 0.1 Hz ~10 khz

σ Amplitude Jitter Measurement AJ = f f high low S ( f ) df ε Amplitude Noise PSD [/Hz] 10-4 10-6 10-8 10-10 Stab.ON / RF OFF Stab.ON / RF ON rms Amplitude JItter RF ON 0.11 RF OFF 0.03 10-12 0.01 0.1 1 10 100 1000 10 4 10 5 10 6 Frequency [Hz] Amplitude Noise PSD Integral range : 0.1 Hz ~10 khz

Future Schedule Characterization of the 357MHz Seed Laser system Timing jitter and Amplitude jitter etc ~31, July Combining all components Seed, Amplifier, Pockles Cells, BBO etc ~31, July Slicing Laser Pulse using Pockles Cell ~6, August Laser Amplifier Experiments & Harmonic Generation ~31, August Beam Experiments September~