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CTF3 lasers
Marta Csatari Divall Eric Chevallay, Valentine Fedosseev, Nathalie Lebas, Roberto Losito, Massimo Petrarca, CERN, EN-STI
CTF3 Collaboration meeting6th May 2010
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 D
F 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 D
F 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/
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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.
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
AchievedNot available yet
The laser was not designed for CALIFES parameters
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
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
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%
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
Outline
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
•Photo-injectors for CTF3•Current laser setup•Phase coding•Diagnostics/Results on PHIN•Feedback stabilization•Laser for CLIC
Laser diagnostics
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
•Exceptional stability without feedback stabilization!•Pointing instabilities can be improved by better airflow control•Amplitude feedback system is necessary
Thanks to PHIN team
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
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
•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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
Noise measured on PILOT system
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
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)
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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 demonstrate
Proven 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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
Outline
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
•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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
• 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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
Modifications to the setup
•Using ‘leakage’ wherever we can•No interruption to operation •High repetition rate test are risky and still cannot be performed
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
• 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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
, W
t
0 50 100 150 200 250 300 350 4000
10
20
30
40
50
60
70
t, mks
G,
one
pass
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
, W
t
0 50 100 150 200 250 300 350 4000
10
20
30
40
50
60
70
t, mks
G,
one
pass
0 50 100 150 200 250 300 350 4000
5
10
15
20
25
t, mks
Pou
t, k
Wt
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
Thanks for all, who contributed !
CTF3 Collaboration meeting6th May 2010
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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
• 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 la ted w ith 3% m odulation of the seed
C alcula ted w ith no m odulation of the seed
C alcula ted w ith 1.5% less seed
Effect of 100 kHz seed modulation on the output (PILOT laser 2004 )
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
flsatabspinout
BGF
DPPP
)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
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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% - - -
Marta Csatari DivallCTF3 Collaboration meeting 6th May 2010 Photo-injector laser for CTF3
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