RF Synchronization control and stability Takuya Natsui Oscillator

RF Synchronization, control and stability Takuya Natsui

Oscillator and frequency • 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. • 51. 9 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. 51. 9 MHz will be special order product. • We developed oscillator due to budged.

Basic synchronize system

Beam trigger, laser pulse and RF synchronization KEKB ring RF frequency : 508 MHz Basic synchronize frequency : 10. 38 MHz (2 bunch pulse distance) LLRF frequency in linac : 114 MHz (10. 38 x 11) and 51. 9 (10. 38 x 5) linac RF : 2856 MHz (10. 38 x 11 x 5 x 5) 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 2856 MHz IQ signal 52 MHz IQ signal

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

Nd: YAG laser oscillator at 3 -2

Nd: YAG oscillator

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 WDM coupler SMF Collimator Grating pair 1000 -grooves/mm PEZ LD Pump l/4 P. D. SMF 250 m. W 976 nm Output Isolator Polarizing l/4 l/2 Yb-doped fiber Collimator

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) Oscillator 1 : 2. 38 deg Oscillator 2 : 0. 58 deg

Controlled piezo displacement Yb: YAG fiber oscillator Cavity length of oscillator 1 is varying greatly

Yb: YAG fiber oscillator • The Yb: YAG oscillator is used at A 1 RF gun. • Frequency : 51. 9 MHz • Phase lock RF frequency : 51. 9 MHz and 2856 MHz • Two oscillators are provided • Phase stability Oscillator 1 : 2. 38 deg Oscillator 2 : 0. 58 deg

Laser transport and spot control at cathode

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

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

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