rf synchronization, control and stability takuya natsui
TRANSCRIPT
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.
• 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.
Oscillator and frequency
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 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.
52 MHz
2856 MHz
INPUT 1
INPUT 2
INPUT 3
INPUT 4
2856 MHzBPF
52 MHzBPF
Oscillator signal
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
LD Pump Nd:YAG
Piezoelectric actuator
Photo diode
52 MHz : resonant length 2.88 m x2
to Amplifire
Control circuit
IQ signal571 MHz
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
LDPump
WDMcoupler
Isolator Yb-doped fiber
SMF SMF
Collimator
Collimator
Polarizing
/4l/4l
Output
/2l
250mW976 nm
1000-grooves/mmGrating pair
PEZ
P.D./4l
Synchronization controller
Laser signal
2856 MHz 52 MHzPiezo control voltage output
Yb:YAG fiber oscillatorWe have two oscillators. Basically, they are same.However their stability is not same.
Second oscillator is very stable
Phase stability (sigma)Oscillator1 : 2.38 degOscillator2 : 0.58 deg
Yb:YAG fiber oscillator
Cavity length of oscillator1 is varying greatly
Cont
rolle
d pi
ezo
disp
lace
men
t
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 stabilityOscillator1 : 2.38 deg Oscillator2 : 0.58 deg
Laser transport and spot control at cathode
2w (515 nm) is transported to near RF gun
telescope
BBO (2w to 4w)
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 MHzSynchronize frequency : 114 MHz and 2856 MHz