RF Synchronization, control and stability Takuya Natsui

Laser oscillator must be synchronized to RF in linac. Linac is driven with 2856 MHz RF. Low level RF system uses 114 MHz (= 2856/25) and 51.9 MHz (= 2856/55). The oscillator frequency must be 114 MHz or 51.9 MHz MHz RF was chosen for oscillator frequency for L-band (1.5 GHz) operation. Because initially, it was planned to use L-band accelerating tube. A lot of product oscillators are about 80 MHz MHz will be special order product. We developed oscillator due to budged. Oscillator and frequency

Basic synchronize system

Beam trigger, laser pulse and RF synchronization KEKB ring RF frequency : 508 MHz Basic synchronize frequency : MHz (2 bunch pulse distance) LLRF frequency in linac : 114 MHz (10.38 x11) and 51.9 (10.38 x5) linac RF : 2856 MHz (10.38 x11x5x5) Beam trigger : 50 Hz

Beam trigger, laser pulse and RF synchronization Beam trigger: 50 Hz Synchronized 51.9 MHz RF is used in linac system. Laser oscillator is synchronize the 51.9 MHz RF. Fine phase tuning is done using 571 or 2856 MHz RF. RF gun and accelerator is driven by the 2856 MHz RF.

Oscillator phase detect 52 MHz IQ signal 2856 MHz IQ signal

52 MHz phase detect PID (Proportional-Integral- Derivative) Controller. CPU control voltage control cycle : >10 kHz Piezoelectric controller 2856 MHz IQ signal 52 MHz IQ signal

Nd:YAG laser oscillator at 3-2

Nd:YAG oscillator

The Nd:YAG oscillator is used at 3-2 RF gun. Frequency : 51.9 MHz Phase lock RF frequency : 51.9 MHz and 571 MHz Phase stability : 2.27 deg

Yb:YAG laser oscillator at A-1

Yb:YAG fiber oscillator LD Pump WDM coupler Isolator Yb-doped fiber SMF Collimator Polarizing  Output  250mW 976 nm 1000-grooves/mm Grating pair PEZ P.D. 

Synchronization controller Laser signal 2856 MHz 52 MHz Piezo control voltage output

Yb:YAG fiber oscillator We have two oscillators. Basically, they are same. However their stability is not same. Second oscillator is very stable Phase stability (sigma) Oscillator1 : 2.38 deg Oscillator2 : 0.58 deg

Yb:YAG fiber oscillator Cavity length of oscillator1 is varying greatly Controlled piezo displacement

Yb:YAG fiber oscillator The Yb:YAG oscillator is used at A1 RF gun. Frequency : 51.9 MHz Phase lock RF frequency : 51.9 MHz and 2856 MHz Two oscillators are provided Phase stability Oscillator1 : 2.38 deg Oscillator2 : 0.58 deg

Laser transport and spot control at cathode

2  (515 nm) is transported to near RF gun

telescope BBO (2  to 4  ) Remote control mirror

By using the reflection of the wave plate, laser profile is being monitored.

Plan 114 MHz oscillator being developed. (114 MHz synchronize RF can be used. L-band was no longer required) Menlo Systems company product laser oscillator will be install. Frequency : 114 MHz Synchronize frequency : 114 MHz and 2856 MHz