SLAC XFEL Short Bunch Measurement and Timing Workshop

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Current status of the FERMI project(slides provided by Rene Bakker)

Photoinjector laser system and related jitter reduction issues

►required parameters►main concerns ►near future experiments

OUTLINE

ON SOME TIMING JITTER ISSUES FOR THE FERMI  FELPHOTOINJECTOR LASER SYSTEM

Presented by M.B.DanailovLaser Lab, Sincrotrone Trieste

danailovm@elettra.trieste.it

SLAC XFEL Short Bunch Measurement and Timing Workshop

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ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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1 GeV Linac(existing)

ELETTRA2-GeV 3rd generation storage-ring

(existing)

ExperimentalUser Hall

(new)

UndulatorBuilding

(new)

Booster Synchrotron(under construction)

Present linac availability:22 h/day

runs presently 3000 h/year, 24 h/day for special studies

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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• Key features:

– Development of a user-facility.

– Based on existing 1-GeV S-band linac infrastructure.

• Specifications:

– Spectral range (2 undulator lines):

1. 100 – 40 nm ( 12 – 30 eV): FEL-1

22 40 – 10 nm ( 30 – 124 eV): FEL-2

– Flexible polarization.

– Seeded operation (SASE as optional).

– Short pulses (sub-ps < 100 fs RMS).

– 50 Hz repetition rate, 1 micro-pulse per macro-pulse.

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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Present status:

•Funding granted

•Linac serves as injector for ELETTRA

2005 – 2006:

(available for FERMI : 22 h/day)

•Construction of a new full-energy injector (booster) for ELETTRA

•Commencement of FEL construction

2007 …………

•Implementation and use of the linac FEL user-facility

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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oldinjector

newinjector

acceleratorS0 – S7

Injector

0 .0 0 .5 1 .0 m1.5

Present Injector

by-pass

RF photo-gun accelerator

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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S0

oldinjector

newinjector S1 – S5 S6 – S7

bunch compressor

2

bunch compressor

1

BC2 linaclinaclinac

harmoniccavity(new)

BC1

newinjector

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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FEL-1 user stationsseed

BC2

linac

FEL-2seed

linac

boosteraccelerator

harmoniccavity

BC1

newrf photo-injector

FEL-1 FEL-2

100 40 40 10 nm Wavelength Target

10 31 25 124 eV

Electron Beam Energy 0.70 0.55 1.00 GeV Bunch Charge 1.0 1.0 nC Peak Current 0.8 2.5 kA Bunch Duration (rms) 500 160 fs Energy Spread (rms) 0.5 1.0 MeV Normalized Emittance 2.0 1.5 10-6 m

Undulator Period 52 36.6 mm

30 % tunabilityE

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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FEL

• online diagnostics

• focused beam

• direct unfocussed beam

• monochromatized beam

spontaneousradiator

synchronizedlaser

MasterOscillator

RFphoto-cathodelaser P&P lasers

timingdiagnostics

linac FEL

feedback

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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elec tron beam

seeding pulsee.g., 50 fs

2 seednd

w asted part ofthe elec tron beam

H GH G output

M 1S

U 1 M 2 U 2

0/52

~ 10 nm

0/5 ~ 50 nm

0/ 5~ 50 nm

0 ~ 250 nm

elec tron beam

FE L output

synchoronizedseeding pulse

0

2-Stage High Gain Harmonics Generation

250 nm 50 nm 10 nm

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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electron pulse acceleratingfield in linac

20 ms

~ 2.5 s

20 ms

~ 2.5 s

e.g., 50 ns (20 MHz)

increase of the average brilliance and flux: 40x

FERMI@ELETTRA

SLAC XFEL Short Bunch Measurement and Timing Workshop

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FERMI PHOTOINJECTOR LASER

Rep rate: 10 (50) Hz Pulse duration: 2-10 ps (FWHM), ideal pulse shape: flat-topRise-time: 0.5 ps (10-90%)Spatial profile: top-hat, ~ 1mm 1/e2 radiusFundamental Wavelength 780-800 nmUV wavelength (third harmonic) 260-267 nmPulse energy (for Cu cathode): Compressed IR amplifier output – 6 mJ /10mJUV after THG crystal- 0.6 mJ/0.75 mJUV on the photocathode >0.45 mJ /0.5mJTiming stability with respect to RF : < 0.5/0.3 ps RMSEnergy stability : < 4% RMS / <3 %RMSStability of the beam position on the photocathode : < 3% 1.5%RMS

MAIN PARAMETERS

SLAC XFEL Short Bunch Measurement and Timing Workshop

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FERMI PHOTOINJECTOR LASERLAYOUT

TS: temporal shaping ; PP : pulse picker ; SS – spatial shaping ; Stab – pulse energy stabilization systemcr-cor : cross correlator (SFG intensity -> jitter)

MLLaser

Ampl1(Regen. , 1 KHz)TS

Pump Laser 1

Ampl2 (Multi-pass, 50 Hz)

THGSS

Pump Laser 2

Stab

REF

PP

cr-cor

Error sig ?

SLAC XFEL Short Bunch Measurement and Timing Workshop

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OSCILLATOR JITTER

CURRENTLY CHARACTERIZED:

1.Oscillator : - home made mirror dispersion controlled (MDC) Cr:LiSAF laser- Ti:S oscillator with prism dispersion control

2. Phase-locking : Commercial CLX-1100 Timing Stabiliser , based on single band (100 MHz) PL loop , mixer

Performance: <200 fs RMS short term stability in noise protected environment

Increase to few ps in presence of acoustic noise

STRATEGY FOR IMPROVEMENT:1.Oscillator:- MDC Ti:S laser - Frequency-doubled Er-doped fiber laser2.Phase-locking:- Use of double band-loop (GHz detector working at harmonic of the

rep rate)- Digital phase detector based error measurement

SLAC XFEL Short Bunch Measurement and Timing Workshop

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FERMI BEAM TRANSPORT SYSTEM

To phase det

PSD1

GunOpen questions:-Ray tracing of the transport optics (Relay imaging?)

-CW pilot beam for fast opt path monitoring- Low vacuum path between laser hutch and gun

Grating

T

Relay imaging

Low vacuum enclosure ?

PSD2

SLAC XFEL Short Bunch Measurement and Timing Workshop

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SUMMARY

- We hope that the stand-by period of FERMI is about to end

- Timing and synchronization would be crucial for the system

- Near future tasks on the laser side:

►decision on the femtosecond oscillator type► further development of digital phase detector based jitter monitoring ►study of diode-pumped regenerative amplifier jitter (cross-correlator based jitter measurement) ► ray tracing of beam transport system►layout of overall timing system