ctf3 lasers

CTF3 lasers

Marta Csatari Divall Eric Chevallay, Valentine Fedosseev, Nathalie Lebas, Roberto Losito, Massimo Petrarca, CERN, EN-STI

CTF3 Collaboration meeting6th May 2010

http://www.cea.fr/

http://www.stfc.ac.uk/

http://www.mi.infn.it/indexIT.shtml

Outline

Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3

•Photo-injectors for CTF3•Current laser setup•Results on PHIN•Feedback stabilization•Phase coding•Laser for CLIC•Future plans

Photo-injectors for CTF3

D FFD

D F D

D F D D F D

D F D

DF DF DF DF DF DF DF DF DF

D F DF DF D

D FFFDD

D F DD F D

D F DD F D D F DD F D

D F DD F D

DF DF DF DF DF DF DF DF DF DFDF DF DF DF DF DF DF DF DF DF DF DF DF DF DF DF

D F DD F DF DF DF DF D

Drive Beam Accelerator

Delay Loop:2 Combiner Ring: x4

CLEX2 beams test area

CALIFES Probe beam photo-injector

Drive Beam Injector thermionic gun

PHIN

PHINDrive beam photo-injector

test stand

UV laser beam

DRIVE beam PROBE beam

Electrons

PHIN CALIFEScharge/bunch (nC) 2.3 0.6

gate (ns) 1200 19.2bunch spacing(ns) 0.666 0.666bunch length (ps) 10 10Rf reprate (GHz) 1.5 1.5

number of bunches 1802 32machine reprate (Hz) 5 5margine for the laser 1.5 1.5

charge stability <0.25% <3%QE(%) of Cs2Te cathode 3 0.3

Possible change over in next few years

Machine parameters set the requirement for the laser

http://clic-study.web.cern.ch/clic-study/


Laser requirements

1.5 GHzSynched oscillator

Cw pre-

amplifier

10W

Phase-coding

test

3-pass amplifier

2-pass amplifier

3.5kW 8.3kW 7.8kW14.8mJ in 1.2μs

2ω3.6kW

4.67mJ in 1.2μs 4ω1.25kW

1.5mJ in 1.2μs

Feed-back stab.

PARAMETERS PHIN CALIFES

Laser in UV

laser wavelegth (nm) 262 262energy/micropulse on cathode (nJ) >363 947energy/micropulse laserroom (nJ) 544 1420

energy/macrop. laserroom (uJ) 9.8E+02 4.1E+01mean power (kW) 0.8 2.1

average power at cathode wavelength(W) 0.005 2.E-04

micro/macropulse stability <0.25% <3%

Laser in IR

conversion efficiency 0.1 0.15energy/macropulse in IR (mJ) 9.8 0.3energy/micropulse in IR (uJ) 5.4 9.5

mean power in IR (kW) 8.2 14.2average power on second harmonic (W) 0.49 1.E-03

average power in final amplifier (W) 9 15

Feed-back stab.


AchievedNot available yet

The laser was not designed for CALIFES parameters

Outline



Contributions

Marta Csatari DivallPhotonics Europe April 14, 2010 Stability of a high power diode-pumped Nd:YLF laser system for photo-injector applications at CERN

1.5 GHzSynched oscillator

Cw pre-

amplifier

10W

Phase-coding

test

3-pass amplifier

2-pass amplifier

3.5kW 8.3kW 7.8kW14.8mJ in 1.2μs

2ω3.6kW

4.67mJ in 1.2μs 4ω1.25kW

1.5mJ in 1.2μs

HighQ front end

Cooling

AMP1 head assembly

AMP1 and AMP2

Phase-coding test

Harmonics



http://www.cea.fr/



Amplifiers

AMP1 AMP2Pumping power 15.5 kW 18.8 kW

Rod length x diameter

8cm x 0.7cm (7cm pumped)

12cm x 1cm (11cm pumped)

Number of passes 3 non-collinear 2 collinear

Small signal gain coeff. (1/cm)

1.162 0.253

Steady-state gain 580 4.1

Power output 3.2 kW 8.3 kW

Extractable from pump

53% 49%


NEW!

1047nm 523nm 262 nmRMS stab. (train) 0.23% 0.8%

(0.45%)1.3%(1.6%)

Energy/pulse (μJ) 5.37 2.5 0.87

Pulse length (ps) 7 7 ~5ps

Beamsize (μmXμm) 418 X 372 370 X 224

Conversion efficiency

(T=89% to harmonics)

47%(best 50%)

35%(best 47%)

Crystal - KTP 11mm ADP [email protected]

Harmonic stages

Preliminary measurement on response to long train

1.2 μs

•1 cm KDP•18% efficiency•Flat response•Beam size/ shape to be optimized

Amp2 as in table

Amp1 onlyX4 less intensity


http://www.cea.fr/

Outline


•Photo-injectors for CTF3•Current laser setup•Phase coding•Diagnostics/Results on PHIN•Feedback stabilization•Laser for CLIC

Laser diagnostics


2δ b

eam

radi

us (m

m)

Distance from 4th harmonic crystal (mm)

Beam transport~11m71% to cathode

PHIN

•Transmission is low for CALIFES line•Pointing instabilities are high due to long distances•Closer to the gun would be better•Automated measurement system needed

~70m64% to cathode under vacuum

CALIFES

Current status on PHIN pointingLaser position/size

Electron beam position/size

Size(mm)

Movement (mm)

Size(mm)

Movement(mm)

x y δx δy x y δx δy

best

0.74 0.64 0.1520%

0.1320%

1.46 1.76 0.641%

0.6537%

worst

0.71 0.67 0.2434%

0.2740%

1.55 2.86 0.7146%

0.6723%

Taken with virtual cathode camera and OTR screen camera


Current status on PHIN amplitude

Amplitude stability Train length

Laser energy (nJ)

Current/ bunch(nC)

(ns)

best 3691.3% RMS

1.50.8% RMS

1250

worst

3302.6%

12.4%

1300

Macropulsestability

IR Green UV

Measured (no sat. exp.)

0.23% 0.8%(0.45%)

1.3%(1.6%)

In PHIN

0.362 0.364 0.366 0.368 0.37 0.372 0.374 0.376 0.378 0.38 0.3820

20

40

60

80

100

120

140

PHIN Current

Current: sigma =0.8 %

In laser room


•Exceptional stability without feedback stabilization!•Pointing instabilities can be improved by better airflow control•Amplitude feedback system is necessary

Thanks to PHIN team

Outline



Sources of instabilities

Amplitude Pointing

• Electrical noise/power supplier noise

• Pumping diodes

• Seed source (osc+preamp)

• Phase coding

• Pointing (amplification + harmonic stages)

• Thermal drifts

• Mechanical vibration

• Water cooling system

• Air conditioning(temperature variation+ airflow)

• Vibration

• Airflow in beam transport

• Lack of relay imaging


•Some also affecting the measurement system!

Sources of instabilities

Improving the environment for the laser is necessary:

•Better temperature stabilization•Less airflow, better enclosure (planned for May 2010)•Move the laser closer to the gun•Change to solid metal mirror

UV train energy

(mJ)

RMS amplitude

stabilityReflectivity

0.264 4.56% 69% 1: on small crack

0.334 2.69% 87.4% 2: on reflective surface

0.167 10.26% 43.7% 3: on big crack

Mirror inside the gun


Scheme to improve stability

Could be reversed for feed forward optionIn TESLA this system was invented by I. Will and his group0.7% rms stability was achieved from 3% with 70% transmission

•Similar system tested at RAL with 4 μs speed →0.25%RMS over 140 μs in the UV•Commercial LASS-II by Conoptics at green wavelength1/1@ 500kHz (Int. Ref. Mode) 5/1 @ 100kHz 18/1 @50kHz 100/1 @10kHz 200/1 @1kHz

250/1 @200hz

Custom design for quasi-cw available•EO modulators ordered for in house tests•System specifications by spring 2011

HOW to measure?• Development of a measurement system with >104 dynamic range is necessary• Challenging task with the phase-coded short train• More detailed fast noise measurements planned for 2010


Noise measured on PILOT system

Outline



Phase-coding

Lens system

Pockels cell

waveplate

Polarizer

5%

55%Losses in %

T=38%

waveplate

2%

Full power train from amplifiers

Polarizer Polarizer2%2% 2% 2%

With type2 crystal we could get T=80%

Alternative scheme•Driver specification is very demanding (3.6MHz, fast rise time ,high average power)• Monitor latest status for available drivers on the market

Slow switching demonstratedRecombination and delay measured•Damage due to the high input power, only 10mW output•RF driver is not up to our specification(see picture)

Driver response tosquare input(voltage applied to modulator)


Oscillator 320mW

Fiber coupler

EO modulator

splitter

333ps delay

Variable attenuator

Fiber outcoupler

20%

82%

11%

Losses in %

EO modulator

11%

waveplate

2%

20%

20%82%

T=9%

NEW scheme •Components in purchasing•Booster amplifier ordered in Feb/2010•Planned commissioning on PHIN autumn/2010

Booster amplifier300mW


Laser driven photo-injector option

ADVANTAGES To demonstrateProven capability to synchronize to external RF source

Amplitude stability <0.25% RMS for PHIN<0.1% RMS for CLIC

Flexibility for timing structure, single pulse operation

Working phase-coding system

Size, shape, pulselength, energy can be optimized for machine

Reliable long term operation(~1000 hour running time during 2009 is already good)

Can produce polarized electrons High charge

Gives smaller transverse emittance

No energy tails (from the laser)

No satellites


Outline


•Photo-injectors for CTF3•Current laser setup•Results on PHIN•Phase coding•Feedback stabilization•Lasers for CLIC•Future plans

Lasers for CLICcurrent Feas Study CLIC in green CLIC SLAC

I.Ross (2001) electrons (*10^9) 3.72 602.3 8.4 8.4 8.4 charge (nC) 0.6

1200 91600 140371 140371 gate (ns) 156 300 6000.666 2.13 1.992 1.992 bunch spacing(ns) 0.5 cw

1.5 0.5 0.5 0.5 Rf reprate (GHz) 2 cw1802 43005 70467 70467 number of bunches 312

5 100 100 100 machine reprate (Hz) 100 120 1201.5 2.9 2.9 2.9 beamshaping/feedback/efficiency/transport

3 2.3 3 2 QE(%) 0.3 0.3262 262 262 532 laser wavelegth (nm) 780 865363 1729 1325 979 energy/micropulse on cathode (nJ) 317.9

544 5013 3843 2839 energy/micropulse laserroom (nJ) 476.9 NA9.8E+02 2.2E+05 2.7E+05 2.0E+05 energy/macrop. laserroom (uJ) 148.8 500 0

0.8 2.4 1.9 1.4 mean power (kW) 1.0 1.7

0.005 22 27 20 average power at cathode wavelength(W) 14.88 601.30% <0.5% <0.1% <0.1% micro/macropulse stability 1% <0.5%

0.1 0.05 0.1 0.35 conversion efficiency0.6 0.6 0.6 IR beamtransport/chopping

9.8 7185.6 2708.1 571.6 energy/macropulse in IR (mJ)5.4 100.3 38.4 8.1 energy/micropulse in IR (uJ)8.2 47.1 19.3 4.1 mean power in IR (kW)

0.49 431 271 57 average power on second harmonic (W)9 659 405 86 average power in final amplifier (W)

DRIVE beam for CLIC POLARIZED SOURCE FOR CLIC

Elec

tron

s

Elec

tron

s

Lase

r

Lase

r


• Lack of laser time for research development on the laser

• Long train operation for CLIC (140 μs)• High average power operation (100Hz)• Stability and stabilization• (Phase coding on the way independently from operation

until installation on PHIN ~October 2010)

Main challenges identified


Modifications to the setup

•Using ‘leakage’ wherever we can•No interruption to operation •High repetition rate test are risky and still cannot be performed


• Laser design was for long trains of the CLIC drive beam• CALIFES requires only up to 226 pulses (160ns) • 1μJ in the UV is necessary for short train, which have not been delivered yet• CALIFES will be used as a diagnostic test bench until 2015 at least

•~60kEuro for replacing old parts•The footprint is 60cm X 150 cm + the oscillator•Deliverable by Spring 2011•In collaboration with IAP for amplification•Rest of the system needs new oscillatorFor <1% change at the output the switch on

time has to be <350ns accurate<1% variation over the train at nominal energy


Independent laser system for CALIFES

This is how long the CALIFES train is

Allow the amplifier to store the energy before pulses arrive

Higher energy can be reachedStability needs to be investigated

PILOT laser tested on CTF2

• 500MHz front end and the existing amplifiers could be used for tests for CLIC• With reprate tripling configuration PHIN could still be used as it is • High repetition rate operation/fracture/thermal lensing to be studied• Non steady-state operation and pre-pumping to be tested• It would also be a useful source for cathode studies• Commercial oscillator+ pre-amplifier+ harmonic stages is available

(up to 30W in the IR ~15W in green without amplification)

•~200kEuro•4 months from order•3 months for tender•After proof of new configuration for CALIFES laser


New source for PHIN laser and CLIC

Current amplifiers in a pre-pumped mode with a pre-shaped pulse

0 50 100 150 200 250 300 350 4000

1

2

3

4

5

6

7

8

9

10

t, mks

Pin

, Wt

0 50 100 150 200 250 300 350 4000

10

20

30

40

50

60

70

t, mks

G, o

ne p

ass

0 50 100 150 200 250 300 350 4000

5

10

15

20

25

t, mks

Pou

t, k

Wt

0 50 100 150 200 250 300 350 4000

1

2

3

4

5

6

7

8

9

10

t, mks

Pin

, Wt

0 50 100 150 200 250 300 350 4000

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20

30

40

50

60

70

t, mks

G, o

ne p

ass

0 50 100 150 200 250 300 350 4000

5

10

15

20

25

t, mks

Pou

t, kW

t

Pre-shaped input pulse After 1st amplifierAfter 2nd amplifier

By Mikhail Martyanov from IAP

•~20kEuro•3-4 months development for driver electronics•5 weeks testing•In collaboration with IAP •Stability can be an issue

•1 year for tender for diodes/drivers and chiller•With original design 600kEuro•STFC doing feasibility for SLAB geometry

Steady state operation with an additional amplifier

•We are working well above saturation fluence•We are close to fracture limit•Slab amplifier might be better solution•Further feasibility is required in 2010/2011


Feasibility for CLIC laser

Future plans

2010•Detailed noise measurements (laser and PHIN)•Improved laser environment by autumn•Implementation and test of phase-coding

2011•Implementation and test of feedback stabilization system•Noise measurements on the machine•Long train harmonics stages•Design studies for CLIC laser


Thanks for all, who contributed !

CTF3 Collaboration meeting6th May 2010

http://www.cea.fr/


Harmonic stages

50% conversion efficiency

KDP-I, 82 4th harm. efficiency

10 mm 0.247.5 mm 0.235 mm 0.21ADP-I,9020mm 0.39

40% conversion efficiency

Mikhail Martyanov, Grigory Luchinin, Vladimir Lozhkarev IAP

G. CHEYMOL- M. GILBERT CEA

bypass for PHIN

Pulse Picker


http://www.cea.fr/

• Response time of the amplifier will depend on the gain and the relaxation time and output fluence• Fast input variations will not be damped

Noise response

-60 -50 -40 -30 -20 -10 0Tim e (m icrosecond)

0.80

0.85

0.90

0.95

1.00

Pho

to d

iode

sig

nal b

efor

e th

e P

ocke

ls c

ell (

Arb

. uni

ts)

5-pass sim ulation

M easured

C alcu lated w ith 3% m odula tion of the seed

C alcu lated w ith no m odulation o f the seed

C alcu lated w ith 1.5% less seed

Effect of 100 kHz seed modulation on the output (PILOT laser 2004 )


flsatabspinout

BGFDPPP

)1(ln4

2

Oscillator and preamp from HighQ< 0.2 % rms above the 100 kHz noise region<1% rms below the 100kHz noise region

Pumping diodesCurrent overshoot <1%Ripples <1%Temperature

• The best technology for the time was bought• We are more sensitive to pump variation• Stabilized diode technology should be investigated• 0.33% RMS stability is measured in the IR

How is the output power affected by the input parameters?

Steady-state MOPA

Interlinked with all the others



Photo-injectors around the world ELSA (FEL) FLASH (FEL) TESLA (FEL) APSPDL ELETTRA PHIN Material Nd:YAG Nd:YLF Nd:YLF

Nd:Glass Nd:Glass Ti:Saph Nd:YLF

Pulse length 30ps on cathode 4.4ps on cathode 20ps square 2-10ps 6-15ps (grating)

6ps on cathode

Pumping Flashlamp Diode and flashlamp

Flashlamp Flashlamp Diode Diode

Harmonic

BBO 2nd

LBO 2nd BBO 4th

3rd harmonic and mixing with glass laser

BBO 2nd and 4th (15% overall)

3rd (15% overall)

KTP 2nd ADP 4th

(14% overall) Wavelength on cathode 532nm 262 nm 263nm 263nm 261nm 262nm Cathode K2CSSb Cs2Te Cs2Te Cs2Te Copper Cs2Te Macropulse reprate 1Hz Up to 10Hz 10 Hz 6Hz Up to 50Hz 1-5 Hz Micropulse reprate 14.44MHz 27 MHz 1 MHz Single Single 1.5 GHz

Pulstrain length 150μsec 1pulse- 800 μs

800 μs Single Single 1.3 microsec

Energy/pulse IR 10 μJ 300 μJ 200 μJ 208 μJ 15000 μJ 5μJ Macro pulse RMS stability

3% ? 3% (<10%)

4.3% (1.7% at lower energy)

0.8% 1.5-3% (<0.5% in IR)

Micropulse RMS stability

? 1-2% <5% <0.8%

Stabilizer Pockels-cell (PC)

? PC and flashlamp

- Non Non yet

Transmission 67% - ? - - - Macrostab 1% <1% 0.7% - - - Microstab 0.8% 0.6% 0.9% - - -


Long train test bench• Using the rejected beam after 1st Pockels-cell• This would allow us to do independent tests during CALIFES operation• Long train studies on the harmonic stages should be done with existing

amplifiers• Feedback stabilization and stability measurements could be carried out at

different wavelengths

~30kEuro for hardware2-3 months for stability measurements (starting summer 2010)Specification of feedback stabilization system (by end of 2010)4-6 weeks harmonics studies and fracture limit test (September 2010)2-3 months crystal temperature stabilizer development2 months feedback stabilization with new electronics (by spring 2011)

Starting summer 2010

ctf3 lasers

Documents

ctf3 photoinjectors

ctf3current laser setupresults

bunch spacingns0

charge stability

combiner ring

valentine fedosseev

nathalie lebas

roberto losito