CTF3 Collaboration meeting – CERN, 16-17 January 2007

Laser system schematic

24

1.55 s

200 s, 5-50 Hz

15 kW10 J

270 s~2332 pulses370 nJ/pulse

~2332 e- bunches2.33 nC/bunch

Beam conditioner

1.5 GHzNd:YLF

oscillator

400 s, 5-50 Hz

Diode pump 18 kW pk

3 kW

2 J

3-pass Nd:YLF amplifier

x300

CWpreamp

3 pass Nd:YLF amplifier

x5

200 s, 5-50 Hz

Diode pump 22 kW pk

Optical gate (Pockels cell)

Energy stabiliser(Pockels cell)

Feedback stabilisation

Phasecoding

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Practical layout

High Qpreamp

High Qoscillator

Coding

Faraday isolator

Amp 1

Amp 2

1.54 sslicing

Noisecontrol

1 pulseslicing

HG HG

Thermallensing correction

300 cm

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Amplifier head design

Laser head assembly

Nd:YLF rod• 7mm diameter 8 cm long – Amp. 1• 10 mm diameter 11 cm long – Amp. 2• 1% doping level• Deep surface etching for higher fracture limit

Glass tube

The rod

water

Dio

des

Lens

5 Diode laser stucks• 18 kW total peak power – Amp. 1• 22 kW total peak power – Amp. 2• 400 s – Amp.1• 200 s – Amp.2

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Amplifier 1

• Amp 1 operational and tested at 5 Hz and 50 Hz

• Rod failure at 50 Hz may be due to non-saturated operation

• Expected output has been delivered (actually slightly exceeded)

• Near-field uniformity should improve with better rod

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Amplifier 1

Near-field profile is flattened by saturationbut shows some effectsof rod inhomogeneities

0 1 0 0 2 0 0 3 0 0 4 0 0

Tim e (s )

0

2 0 0

4 0 0

6 0 0

Ga

in

0

1 0 0 0

2 0 0 0

3 0 0 0

Pow

er (W

)

• Measured output from Amp 1exceeds target power (3 kW from 3 passes)

• Output saturates in agreementwith model

0 50 100 150 200 250 300 350 4000

1000

2000

3000

4000

100

200

300

400

500

Diode current: 90A

Time (microsec)

Pow

er (

W)

Gai

n

Measured at RAL Measured at CERN

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Amplifier 2

0 1 0 0 2 0 0 3 0 0 4 0 0

Time (s)

0

1 0 0 0

2 0 0 0

3 0 0 0

Ga

in0

3 0 0 0

6 0 0 0

9 0 0 0

1 2 0 0 0

Pow

er (W

)

22.8 kW

21.5 kW

2 pa ss es 20. 2 k W

1 pa ss 20 .2 k W

• 10kW from Amp 2 corresponds to 6.7J/pulse

• Beam uniformity is better than Amp 1 (fine fringes are an artefact) but rod is underfilled

• Overfilling improves saturation so steady state is reached but energy is reduced

0 1 0 0 2 0 0 3 0 0 4 0 0

Time (s)

0

1 0 0 0

2 0 0 0

3 0 0 0

Ga

in0

2 0 0 0

4 0 0 0

6 0 0 0

8 0 0 0

1 0 0 0 0

Pow

er (W

)

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Pulse slicing

-0.2

0

0.2

0.4

0.6

0.8

1

-0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

• Risetime is ~4ns

• Extinction ratio, throughput and level of induced noise remain to be optimised (noise level in above trace is misleading)

• Power handling, with additional AOM, remains to be confirmed

6 8 10 1 2 14

Time (ns)

-0.0 1

0

0.0 1

0.0 2

0.0 3

0.0 4

0.0 5

PD

Sig

nal

(V

)

• Test of 1.54s Pockels cell and driver confirms triggering and basic operation

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Frequency multiplying

• Crystals are available fortwo frequency quadruplingschemes:

2 × type I in BBO (preferred)

Type II in KTP + type I in BBO (allows two IR polarisations,perhaps for 3 GHz multiplexing)

• Tests with Amp 1 (low energy) showed an IR-UV conversion efficiency of up to 7%

Extrapolation to Amp 2 should allow system specification to be met

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Task listing

Oscillator & preamplifier Complete – April 2005

Amplifier 1 (5 Hz) Complete – April 2006

1.54 s slicing (no AOM) Demonstrated – July 2006

Amplifier 2 (5 Hz) Demonstrated – July 2006

Phase coding Designed

Frequency multiplying Demonstrated with Amp 1 – August 2006

Safety and machine protection After delivery

Coding finalisation After delivery

Frequency multiplying finalisation After delivery

Amplitude stabilisation After delivery

Single-pulse and AOM slicing After delivery

50 Hz testing After delivery

50Hz thermal lensing correction After delivery

Laser system shipped from RAL to CERN at end of August 2006

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Lasers at CERN

• Oscillator in operation – September 2006 • Preamplifier in operation after service by High Q Laser – November 2006• Amplifier 1 in operation – November 2006• Amplifier 2 assembled and tested (beams not optimized) – January 2007

2nd amplifier

Pockels cell

Breadboard

Laser beam to cathode

Phase coding

Faraday isolator

1st amplifier

HighQ oscillator

HighQ amplifier

Flipping mirrors

Beam dump

f = 300 mm

f = - 250 mm

f = -100 mm/2

f = 100 mm

f = - 150 mm

f = 400 mm

f = - 100 mm f = 800 mmBBO SHG

BBO FHG f = 300 mm

Laser beam to CALIFES

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Oscillator

PreamplifierAmplifier 1Amplifier 2

Pulse slicingPockels cell

Fiber-optics coding system

CERN installation

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Amplifiers hardware

Amplifier 2 Chillers for amplifier diodes55 l/min and 75 l/min

Drivers for 5 diode laser stucks of Amplifier 2

120 A each

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Pulse coding

EO Modulator

140.7 ns macropulses Variable

delay

Variable attenuator

140.7 + 0.333 ns delay

320 mW in from oscillator

~30 mW out to preamp

• Fibre modulation, based on telecoms technology, is fast but lossy andlimited in average power

• Measurements on the High Q system suggest 10dB loss before the preamp results in <3dB output reduction

• Delay can be adjusted by varying the fibre temperature (~0.5ps/°C)

• Attenuation can be controlled by varying the fibre bending losses

• Preliminary assembly and tests of temperature tuning were carried out at RAL

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Pulse slicing with AOM

AO Deflector

Output to

doublerPockels cell

Input from Amp 2

RF Driver

Pockels Driver

AO deflector could reducepower loading on Pockels cellby up to 80% for most ofthe macropulse

QS41-5C-S-SS2

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Laser-room DB gun 15 m 0.05 s Laser-room PB gun 75 m 0.25 sPhoto-injector Delay Loop 85 m 0.2833 s PB macro-pulse length 0.021312 sDelay Loop 42 m 0.14 sTL Delay Loop Comb. Ring 30 m 0.1 s TOTAL time 0.271312 sCombiner Ring 84 m 0.28 s Conv. 1.5 GHz to 3 GHz 0.021312 sTL Comb. ring Probe Beam 48 m 0.16 s PB selection after DB 1.860709 sTotal with 1 DL and 4.5 C. Ring 598 m 1.9933 sMacro pulse length 0.14 sFilling time of PETS+Acc. 0.02 sTOTAL time 2.1533 s

First pulse of the Drive beam Probe Beam

Timing for CLEX Probe-beam

CTF3 Collaboration meeting – CERN, 16-17 January 2007

Thank you for your attention

AcknowledgmentsRAL

Marta DivalGraeme HirstKurdi GaborEmma SpringateBill MartinIan Musgrave

CERN

Guy SuberlucqRoberto LositoNathalie ChampaultArvind Kumar