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Recent results of the femto-second synchronization system Florian Löhl December 20 th. Optical timing system. to low level RF. optical length stabilized fiber links. laser to RF conversion. fiber couplers. Master Laser Oscillator (erbium-doped fiber laser). - PowerPoint PPT Presentation
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Recent results of the femto-second synchronization system
Florian Löhl
December 20th
Florian Löhl XFEL Meeting, December 20th
Optical timing system
Master LaserOscillator
(erbium-dopedfiber laser)
optical length stabilized fiber links
fiber couplers
laser to RFconversion
low-noisemicrowaveoscillator
phase lock loop
to low level RF
direct use of laser pulses
• beam arrival-time monitors• beam position monitors• optical down-converters• seeding of amplifiers• synchronization of other lasers (cross correlation)…
Florian Löhl XFEL Meeting, December 20th
Current projects(Coordinator: H. Schlarb)
Master laser system (MLO) (A. Winter, MIT)Fiber link stabilization (F. Loehl, MIT)Laser to RF conversion (F. Ludwig, B. Lorbeer, M. Felber, MIT)Bunch arrival time monitor (F. Loehl)BPMs in magnetic chicanes (K. Hacker)New down-converter for cavity regulation (F. Ludwig, M. Hoffmann, LLRF-Group)Laser oscillator for CPA system (ORS) (N. Javahiraly, A. Winter)Fast motor control and position encoder readout (J. Thomas, …)DOOCS compatible laser diode driver (A. Winter, FEB, MVP)Digital regulation of master laser system (W. Jalmuzna, LLRF-Group)Digital regulation of fiber links (G. Petrosyan, …)Drift characterization of photo diodes (B. Lorbeer, F. Ludwig, …)Drift reduced RF mixer (J. Mueller, F. Ludwig)DOOCS compatible polarization controller (M. Felber, …)Fast regulation of cavities with beam based measurements (LLRF-Group)Development of precise photo diode read out (K.H. Matthiesen, …)Cross-correlation of pump-probe laser and timing system (V. Arsov, …)Development of analog PI controller / piezo driver (N. Ignachine, …)Design of 130 MHz ADC board (DWC, BAM, BPM) (P.Strzalkowski, M. Hoffmann, …)Characterization of EDFAs (J. Mueller)Simulation of optical pulse propagation (H. Schlarb, F.Loehl...)
Florian Löhl XFEL Meeting, December 20th
Master laser oscillator (MLO)
Courtesy of A. Winter
• Dispersion managed stretched pulse fiber-laser• Gain medium Erbium, (center at 1550 nm) • High pulse energy (up to ~ 1 nJ)• Pulse duration: ~ 100 fs FWHM• Repetition rate: 54 MHz• Integrated timing jitter (1 kHz – 20 MHz) ~ 10 fs• Integrated amplitude noise (10 Hz – 1 MHz): 0.03 %
Florian Löhl XFEL Meeting, December 20th
Master laser oscillator (MLO)
Courtesy of A. Winter
Florian Löhl XFEL Meeting, December 20th
Fiber link stabilization
Florian Löhl XFEL Meeting, December 20th
Fiber link stabilization
Florian Löhl XFEL Meeting, December 20th
Fiber link stabilization
Timing jitter: ~ 9.7 fs Timing jitter: ~ 9.2 fs Detector noise floor: ~ 8.2 fs
Florian Löhl XFEL Meeting, December 20th
Fiber link installation
Optical fiber test section will be installed in Hall 1• test of specialty fibers• development of fiber link stabilization
Installation status:Installation of pipes is already done or will be done this weekInstallation of first optical fibers to be done first week of JanuarySplicing planned for January / February
Top view
P1P2P3
P5
P4P6
P7
P8P9
P10
P1-10 fiber patch panel Synchronization hutch (start point of all links)
Installation of optical fibers in the TTF linac
Florian Löhl XFEL Meeting, December 20th
New fiber laser development from MIT:194 MHz laser (potentially scaleable to > 500 MHz)
FWHM167 fs
1 Hz – 1MHz: 0.004 %
1 kHz – 10 MHz: 29 fs
Cor
tesy
of
Jeff
Che
n
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion
Direct conversion with PD– temperature drifts– AM to PM conversion*– noise limitation due to low power
in spectral line of PD output
~~~
PD BPF
Injection Locking– temperature drifts of PD– AM to PM conversion of PD*+ DRO determines high frequency
noise+ entire photo detector signal used
laser pulses
PD
Low noise DRO(f = n*frep)
laser pulsesresonator
phase shifter
t
frepf = n*frep
f = n*frep
frep
f = n* frep
Optical division of distributed frequency
laser pulses
frep
AOM / EOM
modulation voltage
frep / n
(*) typical AM to PM conversion: 1-10ps/mW
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion:sagnac loop
Phase detection in the optical domain:
Cortesy of F. Ludwig
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion:sagnac loop
Phase detection in the optical domain:
Cortesy of F. Ludwig
modulation voltage: frep / 2
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion:sagnac loop
Phase detection in the optical domain:
Cortesy of F. Ludwig
modulation voltage: frep / 2
VCO signal to stabilize (n*frep)
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion:sagnac loop
Phase detection in the optical domain:
Cortesy of F. Ludwig
modulation voltage: frep / 2
VCO signal to stabilize (n*frep)
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion:sagnac loop
Optical to RFDetector 1
MLO
Optical to RFDetector 2
RF PhaseDetector
(0.8fs @10GHz)
RF electronic 2
RF electronic 1
Low noise PI controller(P, I, g, cutoff independent)
Florian Löhl XFEL Meeting, December 20th
Laser to RF conversion:sagnac loop
timing jitter between two VCOs locked via sagnac loop (10 Hz – 10 MHz): 12.8 fs @ 10 GHz
long term drift between the two VCOs: 48 fs over 1 hour (top)
Base line drifts (one VCO connected to same mixer): 50 fs over 8 hours (bottom)Cortesy F. Ludwig
Florian Löhl XFEL Meeting, December 20th
Drift reduced RF mixer
Courtesy of F. Ludwig, J. Mueller
Florian Löhl XFEL Meeting, December 20th
Drift reduced RF mixer
Florian Löhl XFEL Meeting, December 20th
New down converter for cavity regulation
Courtesy of F. Ludwig, LLRF-Group
Noise appears at the DWC output but not on the cavity field!
LNA ADC
LO-input ADC clock
BPFBPF
RF-input 1
I,Q-Detection
I samples
Q samplesLocal RF-Generator
Lookup
Table
Regulation loop
250 kHz switched system 54 MHz CW system:
• uses 54 MHz intermediate frequency• gives together with the high ADC sampling rate the possibility of averaging (reduces noise at high frequencies)• change from active to passive mixers while increasing the power level will reduce also the noise at low
requencies
Florian Löhl XFEL Meeting, December 20th
New down converter for cavity regulation
Courtesy of M. Hoffmann, LLRF-Group
ADC noise reduction by averaging:
fS = 81 MHz, fIF = 54 MHz, ∆t = 1μs
Florian Löhl XFEL Meeting, December 20th
Bunch arrival time monitor (BAM)
sampling time of ADC
40.625 MHz(54 MHz)
The timing information of the electron bunch is transferred into a laser amplitude modulation. This modulation is measured with a photo detector and sampled by a fast ADC.
Florian Löhl XFEL Meeting, December 20th
Bunch arrival time monitor (BAM)
Jitter between two adjacent bunches: ~ 40-50 fs Timing resolution with respect to reference
laser: < 30 fs
Arrival time measurement for all bunches in the bunch train possible! Plan to implement this into feedback
system of LLRF group
Florian Löhl XFEL Meeting, December 20th
Bunch arrival time monitor (BAM)
The signal of the ring pick-up shows a “bump” around the zero-crossing. This bump has a largeorbit dependence.
New design of pick-up (knobs instead of a ring)(design: K. Hacker)
Installation of a first test pick-up is scheduled for January 2007.
17mm14.5mm 6.2mm
1.2mm thickAlumina disk
pick-up currently used: new design:
Florian Löhl XFEL Meeting, December 20th
BPMs in the magnetic chicanes
Beam Path
Pickup
SMA Vacuum Feedthrough
TaperingChannel
BPM
Courtesy of K. Hacker
The arrival time of the pickup signals is measured at both ends with the same technique as used for the bunch arrival time monitor. The beam position is determined from the difference of both arrival times.
Compact!
Florian Löhl XFEL Meeting, December 20th
BPMs in the magnetic chicanes
-15 -10 -5 0 5 10 15-6
-4
-2
0
2
4
6Beam position ( = 18.0 deg)
delta [%]
po
sitio
n (
cm)
R16T166R1666
Measurements done with scope in the tunnel (~ 150 μm resolution)
Blue lines show expected beam position for different energies
Courtesy of K. Hacker
0 0.2 0.4 0.6 0.8 1
-200
-100
0
100
200
simulation and oscilliscope readout
time (ns)
Vo
lts
ACC1 energy change [%]
Agreement between simulated pick-up response (40 GHz, blue) and measured one (8 GHz scope, red)
Florian Löhl XFEL Meeting, December 20th
Regulation of injector using beam based measurements
RF Gun
Photo Cathode Laser
Booster
Chicane BPM (CBPM)
1
2
arrival-time monitors
BPMs bunch compression
monitor(H. Delsim-Hashemi,
B. Schmidt)
Regulation parameters: - photo cathode laser: arrival time- Gun: phase (amplitude not critical)- ACC1: phase, amplitude
Goal: stable bunch compression and arrival time Many different monitor systems and complex regulation algorithms needed!
• Arrival time of photo cathode laser pulses (1st arrival time monitor)• Phase of RF gun (difference between 1st and 2nd arrival time monitor)• Amplitude of booster module (CBPM + BPMs)
(synchrotron light monitor + BPMs)(difference between 3rd and 2nd arrival time monitor)
• Phase of booster module (bunch compression monitor)(fiber laser + EO)
synchrotronlight monitor(C. Gerth)
3
Florian Löhl XFEL Meeting, December 20th
New infrastructure
Florian Löhl XFEL Meeting, December 20th
Conclusion
• Collaboration with MIT is VERY fruitful
• A lot of infrastructure for synchronization R&D is already installed
• Great effort done by many people and groups to reach the goal of a femto-second stable machine
• Demonstration of many schemes is already done
• next big step: construction of complete system (end 2007, completed 2008)
• performance test of complete system
Many thanks for the technical support of the FLA group and for the fruitful collaboration with the LLRF-group!
Fast phase Modulator
ODL PZTSlow phase
shifter
Temperature stabilizeddispersion compensation
module
RF detector
Bal. SHG Det.
Bal. Coh. Det.
Mirror
Digital FB controller
fr/(2n)
Mixer
Optical link
HNLF
SMF
50MHz
Er-fiber laser
ED
FA
LiIO3
/2c
2.2um
1.1um
HeNe/CH4
AOM
3.39um10MHz
InSb 77K
PD
Digital FB controller
Pump
EDFA laser CEO + CW locked
0.6
25
MH
z
2.5
MH
z
BP1100nm
PZT
BP
~~~
62.5MHz1GHz
:100
BP
PPLN
frf0
Ti:Sa CEO stab. &HeNe/CH4 stab.
Bal. Coh. det
FB controller
fr
PP
LN
f r/(
2n
)
Seed/PP laser
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