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

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)…


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...)


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 %


Master laser oscillator (MLO)

Courtesy of A. Winter


Fiber link stabilization





Timing jitter: ~ 9.7 fs Timing jitter: ~ 9.2 fs Detector noise floor: ~ 8.2 fs


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


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


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


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)






VCO signal to stabilize (n*frep)



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)



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


Drift reduced RF mixer

Courtesy of F. Ludwig, J. Mueller


Drift reduced RF mixer


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


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


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.



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



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:


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!


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)


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


New infrastructure


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

Documents

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