Download RF Synchronization, control and stability

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 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
2856 MHz IQ signal
INPUT 1
Oscillator
signal
2856 MHz
BPF
2856 MHz
INPUT 2
INPUT 3
52 MHz
BPF
52 MHz IQ signal
52 MHz
INPUT 4
52 MHz IQ
signal
52 MHz phase detect
PID (Proportional-IntegralDerivative) Controller.
CPU control
2856 MHz IQ signal
voltage control
cycle : >10 kHz
Piezoelectric
controller
Nd:YAG laser oscillator at 3-2
Nd:YAG oscillator
Piezoelectric actuator
Control circuit
IQ signal
52 MHz ： resonant length 2.88 m x2
571 MHz
LD Pump
Nd:YAG
Photo diode
to Am
plifire
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
PEZ
LD
Pump
l/4
P.D.
Collimator
Grating pair
1000-grooves/mm
SMF
250mW
976 nm
Output
Isolator
Polarizing
l/4
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)
Oscillator1 : 2.38 deg
Oscillator2 : 0.58 deg
Controlled piezo displacement
Yb:YAG fiber oscillator
Cavity length of oscillator1 is varying greatly
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
2w (515 nm) is transported to
near RF gun
telescope
Remote control mirror
BBO (2w to 4w)
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