XFEL 2004 at SLAC m. ferianis

Synchronization and phase monitoring: recent results at ELETTRA

• Synchronization experiment using light sources currently available at Elettra

• Streak camera measurements• CW Phase measurements• Status of the “light-to-light” jitter monitor • Single event phase measurement

Mario Ferianis, Miltcho Danailov

SINCROTRONE TRIESTE, Italy

XFEL 2004 at SLAC m. ferianis

Radiation sources currently available at Elettra

• Sources presently available at ELETTRA:– Bending Magnet S12.2 (diagnostic beam line)

• FWHM=30ps tREP 1MHz

– Storage Ring - FEL• FWHM=8ps tREP 4MHz,

– Table top fs-lasers: Ti:Sa and Cr:LiSaf• FWHM110fs tREP 100MHz

• The SR-FEL is “naturally” synchronized to ELETTRA• The table-top lasers may be locked to an external RF

XFEL 2004 at SLAC m. ferianis

Synchronization experiment of a fs Laser to Elettra Sources

Phase Detector PowerSplitter

LPfilter

Piezodriver

Laser cavity

LaserIN

ReferenceIN

Piezoactuator

fREP2=83.2756MHz

fREF=83.2756MHz

SynchrotronRadiation

pulses@4.626MHz

2

NUnit

Synchro-scan

Streak Camera

Streak CameraTiming system

fS-SCAN=250MHz

PowerSplitte

r

Laser Timing

Stabilizer

from Storage Ring RF generatorfRF=499.654MHz

PowerSplitter

Divide-by-6Unit

XFEL 2004 at SLAC m. ferianis

View of the Profile Monitor laboratory with the Cr:LiSAF laser and the Streak Camera

XFEL 2004 at SLAC m. ferianis

laser

2ns

10ns

Streak Camera acquisition:Multi Bunch (2ns spacing) beam+laser @99.93MHz

fREP1=fRF5 = 99.9308MHz

XFEL 2004 at SLAC m. ferianis

880ps

864ns:1 ELETTRA revolution

18 laser pulses

4 Bunch beam (216ns/bunch) + laser@83.275MHz (12ns)

12ns

12ns

440ps

fREP2 =fRF6 = 83.2756MHz

XFEL 2004 at SLAC m. ferianis

5 accumulated acquisitions

Laser phase oscillationsdue to external kick

Elettra 4 bunch beam

180ps

880ps

69ms

XFEL 2004 at SLAC m. ferianis

All three sources

FEL staff courtesy

FELmacropulses

CR:LiSAF trace@83MHz

The “old, good ELETTRA”4bunch @ 4.6MHz

6.7ms

XFEL 2004 at SLAC m. ferianis

Phase Detector AD8302 (02.7GHz) Analog Devices

EX-OR

Low-pass filter

Vector analyser on a chip

XFEL 2004 at SLAC m. ferianis

Vphase vs. frequency @100MHz:Ftot=100kHz TOT=0.135deg

99,940,000

99,960,000

99,980,000

100,000,000

100,020,000

100,040,000

100,060,000

1 67 133 199 265 331 397 463 529 595 661 727 793 859 925 991 105711231189125513210.4670

0.4672

0.4674

0.4676

0.4678

0.4680

0.4682

0.4684

0.4686

0.4688

0.4690

frequency phase

tot=0.135deg; step=13.5mdeg

VSTEP=0.135mV

1deg@100MHz =27.7ps;min=0.187ps (step /2)1deg@3GHz =0.926ps; min=6.25fs

XFEL 2004 at SLAC m. ferianis

Comparison of two phase measurements

AD 8302 Phase

Detector

PowerSplitter

Ceramic Band PassLC filter

Piezo

driver

Laser cavity

LaserIN

ReferenceIN

Piezoactuator

fREP2=83.2705MHz

PowerSplitter

Laser Timing

Stabilizer

Photo diode

R&Sgenerator

A

B

1) V PHASE

Spectrum Analyzer HP3589

Digital Oscilloscope

TEK 7104

2) Phase OUT

XFEL 2004 at SLAC m. ferianis

Spectra of phase noise of the laser locked @ 83.2705MHz

CLX 1100Phase OUTPUT

AD8302 Vphase

XFEL 2004 at SLAC m. ferianis

Locked laser damping timeto an external kick

AD8302 Vphase

100mV/div

CLX phase OUT

20mV/div

300ms

XFEL 2004 at SLAC m. ferianis

Experiment set-up in the SRPM hutch

Phase Detector PowerSplitter

LPfilter

Piezodriver

Laser cavity

LaserIN

ReferenceIN

Piezoactuator

fREP2=83.2756MHz

fREF=83.2756MHz

SynchrotronRadiation

pulses@4.626MHz

Band passfilter 18th

harmonic

Direct light-to-lighton-line jitter

measurement

Sub-psPhase

comparator

2

NUnit

Synchro-scan

Streak Camera

Streak CameraTiming system

fS-SCAN=250MHz

PowerSplitte

r

Laser Timing

Stabilizer

from Storage Ring RF generatorfRF=499.654MHz

PowerSplitter

Divide-by-6Unit

XFEL 2004 at SLAC m. ferianis

Bandpass filter response to 4 Bunch beam,f0=83.275MHz, BW 6.5MHz.

XFEL 2004 at SLAC m. ferianis

AD8302 phase measurement: 6.5MHz filter output vs. reference

(83.275MHz)

V=330mV 33deg

Plot of the phase difference measured with 1GHz scope [deg]

230

240

250

260

270

280

290

0 100 200 300 400time [ns]

XFEL 2004 at SLAC m. ferianis

Narrowband (BW=2.5MHz)bandpass filter

XFEL 2004 at SLAC m. ferianis

FERMI Phase Measurements

• The term “Phase measurement” generally refers to measuring the phase of a signal w.r.t. a reference.

• Rigorously, we can speak about phase when dealing with sinusoidal signals, eventually sinusoidal bursts.

• For FERMI applications, two different “phase” measurements* are needed:– sinusoidal to reference (CW/CW burst measurement)

– pulse to reference (single event measurement)

• For pulsed signals, the phase difference can be defined as the time interval bewteen pulse arrival and next zero crossing of the reference signal.

• The most critical measurement is the second one due to:– required (sub-) ps resolution

– ultra short pulses of limited amplitude (low energy signals)

– low repetition rate (1 to 100Hz)

* APL - Dip. Elettronica ed Informatica, Trieste University and AllTEK Innovation s.r.l.

XFEL 2004 at SLAC m. ferianis

Proposed scheme for single event phase measurement

Pulse stretcher

Beam pulsesignal

Reference signal

“0” Xingdetector

(low jitter)Hold off

Hold off

Time interpolator(SiGe logic)

Pulse stretcher

“0” Xingdetector

(low jitter)

APL - Dip. Elettronica ed Informatica, Trieste University and AllTEK Innovation

XFEL 2004 at SLAC m. ferianis

Zero X-ing detector prototypetests with Pulse Generator:

tPULSE=300ps; APULSE PK-PK=90mV; fREP=10kHz

TRIGGER

CSA803CSampling

Scope

BW=20GHz

INPUT

HP8131A500MHz

Pulse Generator 10mV/div100ps/div

JitterRMS=1. 37ps

TRIGGER

CSA803CSampling

Scope

BW=20GHz

INPUT

HP8131A500MHz

Pulse Generator

“0” X-ingdetector

IN OUTunder

test

100mV/div100ps/div

JitterRMS=1.94ps

Apk-pk=600mV*10 (20dB att) =6V

APL - Dip. Elettronica ed Informatica, Trieste University and AllTEK Innovation s.r.l.

XFEL 2004 at SLAC m. ferianis

tRISE =18pstPULSE =30psAPULSEpk-pk=250mV

Zero X-ing detector prototype tests @ fREP=10Hz

fs laser + Pockels Cell + 25GHz Photodiode

New FocusPhoto DiodeBW=25GHz

“0” Xingdetector

under test

IN OUT

TEK Real time ScopeTRIGGER

CH1

BW=1GHz

CH2

Cr:LiSAFfs laser

PockelsCell

HVdriver

SPLITTER

Amplifier7GHz

Pulsegenerator

-10dB

2Vpk-pk*3.17=6.3V

APL - Dip. Elettronica ed Informatica, Trieste University and AllTEK Innovation

XFEL 2004 at SLAC m. ferianis

Future work

• To complete direct light-to-light phase measurements in 4B mode– Bending Magnet to external fs laser– Bending Magnet to SR-FEL– SR-FEL phase during Q-switch w.r.t. a non modulated RF (?)

• To complete jitter reduction work in the Profile Monitor hutch• To implement phase measurement at low rep rate

– 10Hz i.e. FERMI

• To characterise laser jitter in fiber optic transmission• To study the feasibiltiy of an in-house improved version of

phase locking system (timing stabilizer)