1. Recent results of the femto-second synchronization system
Florian Löhl
December 20th

2. optical length stabilized fiber links
Optical timing system
optical length stabilized fiber links
to low
level RF
laser to RF
conversion
Master Laser
Oscillator
(erbium-doped
fiber laser)
fiber couplers
direct use of laser pulses
beam arrival-time monitors
beam position monitors
optical down-converters
seeding of amplifiers
synchronization of other
lasers (cross correlation) …
phase lock loop
low-noise
microwave
oscillator
Florian Löhl XFEL Meeting, December 20th

3. 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
Göttlicher analog, Eckelmann FPGA, G. Petrosyan Doocs server,
Vetrov digital part)

4. Master laser oscillator (MLO)
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 %
Courtesy of A. Winter
Florian Löhl XFEL Meeting, December 20th

5. Master laser oscillator (MLO)
Courtesy of A. Winter
Florian Löhl XFEL Meeting, December 20th

6. Fiber link stabilization
Florian Löhl XFEL Meeting, December 20th

7. Fiber link stabilization
Florian Löhl XFEL Meeting, December 20th

8. 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

9. 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 week
Installation of first optical fibers to be done first week of January
Splicing planned for January / February
Installation of optical fibers in the TTF linac
Top view
P10 P4 P3 P2 P1 P8 P6 P9 P5 P7
P1-10
fiber patch panel
Synchronization hutch (start point of all links)
Florian Löhl XFEL Meeting, December 20th

10. New fiber laser development from MIT: 194 MHz laser (potentially scaleable to > 500 MHz)
FWHM
167 fs
1 Hz – 1MHz:
0.004 %
1 kHz – 10 MHz:
29 fs
Cortesy of Jeff Chen
Florian Löhl XFEL Meeting, December 20th

11. ~ Laser to RF conversion Optical division of distributed frequency
laser pulses
AOM /
EOM
frep
frep / n
modulation voltage
Direct conversion with PD
temperature drifts
AM to PM conversion*
noise limitation due to low power
in spectral line of PD output
laser pulses
f = n*frep PD
BPF ~
frep
f = n*frep
Injection Locking
temperature drifts of PD
AM to PM conversion of PD*
DRO determines high frequency
noise
entire photo detector signal used
f = n* frep PD
Low noise DRO
(f = n*frep)
laser pulses
resonator
phase shifter
frep
(*) typical AM to PM conversion: 1-10ps/mW t
Florian Löhl XFEL Meeting, December 20th

12. Laser to RF conversion: sagnac loop
Phase detection in the optical domain:
Cortesy of F. Ludwig
Florian Löhl XFEL Meeting, December 20th

13. Laser to RF conversion: sagnac loop
Phase detection in the optical domain:
modulation voltage: frep / 2
Cortesy of F. Ludwig
Florian Löhl XFEL Meeting, December 20th

14. Laser to RF conversion: sagnac loop
Phase detection in the optical domain:
VCO signal to stabilize
(n*frep)
modulation voltage: frep / 2
Cortesy of F. Ludwig
Florian Löhl XFEL Meeting, December 20th

15. Laser to RF conversion: sagnac loop
Phase detection in the optical domain:
VCO signal to stabilize
(n*frep)
modulation voltage: frep / 2
Cortesy of F. Ludwig
Florian Löhl XFEL Meeting, December 20th

16. Laser to RF conversion: sagnac loop
Low noise PI controller
(P, I, g, cutoff independent)
Optical to RF
Detector 1
MLO
RF electronic 1
RF Phase
Detector
Optical to RF
Detector 2
RF electronic 2
Florian Löhl XFEL Meeting, December 20th

17. Laser to RF conversion: sagnac loop
timing jitter between two VCOs locked via sagnac loop (10 Hz – 10 MHz): 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

18. Drift reduced RF mixer Florian Löhl XFEL Meeting, December 20th
Courtesy of F. Ludwig, J. Mueller
Florian Löhl XFEL Meeting, December 20th

19. Drift reduced RF mixer
Florian Löhl XFEL Meeting, December 20th

20. New down converter for cavity regulation
RF-input 1
BPF
BPF
I,Q- Detection
I samples
Lookup
Table
Regulation loop
LNA
ADC
Q samples
Local RF-Generator
LO-input
ADC clock
Noise appears at the DWC
output but not on the cavity field!
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
Courtesy of F. Ludwig, LLRF-Group
Florian Löhl XFEL Meeting, December 20th

21. New down converter for cavity regulation
ADC noise reduction by averaging:
fS = 81 MHz, fIF = 54 MHz, ∆t = 1μs
Courtesy of M. Hoffmann, LLRF-Group
Florian Löhl XFEL Meeting, December 20th

22. Bunch arrival time monitor (BAM)
sampling time of ADC
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

23. Bunch arrival time monitor (BAM)
Jitter between two adjacent bunches: ~ 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

24. Bunch arrival time monitor (BAM)
The signal of the ring pick-up shows a “bump” around the zero-crossing. This bump has a large
orbit 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.
pick-up currently used:
new design:
17mm
14.5mm
6.2mm
1.2mm thick
Alumina disk
Florian Löhl XFEL Meeting, December 20th

25. BPMs in the magnetic chicanes
Compact!
BPM
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.
Beam Path
Pickup
SMA Vacuum Feedthrough
Tapering
Channel
Courtesy of K. Hacker
Florian Löhl XFEL Meeting, December 20th

26. BPMs in the magnetic chicanes
R16
T166
R1666
ACC1 energy change [%]
Measurements done with scope in the tunnel (~ 150 μm resolution)
Blue lines show expected beam position for different energies
Agreement between simulated pick-up response (40 GHz, blue) and measured one (8 GHz scope, red)
Courtesy of K. Hacker
Florian Löhl XFEL Meeting, December 20th

27. Regulation of injector using beam based measurements
Chicane BPM
(CBPM)
Photo Cathode Laser
synchrotron
light monitor
(C. Gerth) 1
arrival-time monitors
RF Gun
Booster 2 3
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)
Florian Löhl XFEL Meeting, December 20th

28. New infrastructure
Florian Löhl XFEL Meeting, December 20th

29. 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!
Florian Löhl XFEL Meeting, December 20th

30. Temperature stabilized dispersion compensation
Fast phase
Modulator
ODL
PZT
Slow phase
shifter
Temperature stabilized
dispersion 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
EDFA 
LiIO3
/2c
2.2um
1.1um
HeNe/CH4
AOM
3.39um
10MHz
InSb 77K PD
Pump
EDFA laser CEO + CW locked
0.625MHz
2.5MHz BP
1100nm ~
62.5MHz 
1GHz
:100
PPLN fr f0
Ti:Sa CEO stab. &
HeNe/CH4 stab.
Bal. Coh. det
FB controller
Seed/PP laser