Cs 2 Te Photocathodes for CTF3 Photoinjectors R. LOSITO - CERN 4/10/2006

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Acknowledgements We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 “Structuring the European Research Area” programme (CARE, contract number RII3-CT ).

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Acknowledgements Probe Beam Photoinjector will be provided and funded by a collaboration between CERN and CEA-Saclay

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors OUTLINE CTF3 overview Photoinjectors’ specs and design Photocathodes Conclusions

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors CTF3 overview

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors CTF3 overview PHASE CODING

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors CTF3 overview Photocathode Specifications:  Film: Cs 2 Te  Quantum efficiency: >3% (Drive beam)  Lifetime: > 40 working hours  Wavelenght: 260 nm

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors CTF3 overview DRIVE BeamPROBE Beam Current in the train3.5 Amps0.23 A, 0.93 A, 1.83 A Charge in each pulse:2.33 nC0.15 nC, 0.6nC Quantum Efficiency3%0.3% (1%) Pulse frequency1.5 GHz, (3 GHz)1.5 GHz; 3GHz Rep rate1÷50 Hz (nominal: 5 Hz)5 Hz

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors CTF3 overview DRIVE BeamPROBE Beam Emittance<25 π.mm.mrad<20 π.mm.mrad Charge stability<0.25% rms<3 % rms Pulse width:10 ps Jitter on pulse position<1 ps Number of pulses23321, 32, 64, 128 Train duration1.5 µs10 ps, 20 ns, 85 ns

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors PHIN overview (drive beam)

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors RF Gun PHIN GUN Courtesy of G. Bienvenu, R. Roux LAL, Orsay

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors RF Gun Monte-Carlo based simulations of the residual pressure Not effective to improve situation by adding pumps providing more than 40 l/s P1 P2 P3 P0

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors RF Gun 0.2 mm Copper in oven 3 days, t° = 550°C Fast cooling with Ar jet 150°C =>No grain size enhancement The residual pressure from copper outgassing should be reduced by at least one order of magnitude (down to mbar) by applying a high T bake-out after brazing. Improvement of static pressure: minimize the out-gassing rate by High temperature bake

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors RF Gun 42 holes drilled in the gun walls (F=4mm) Volume around the holes coated with NEG

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors CERN photocathode Lab was working without interruption since 15 years. The whole line (preparation chamber, DC Gun, transport carrier) has been inspected and repaired. Test coatings have been realised to re-calibrate all the system. Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes photocathodes produced by co-evaporation seem to be quite sensitive to the quality of vacuum

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Measured in DC Gun at 8 MV/m 20 cath.QE(%) Min8.2 Average14.9 Max22.5 Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Points to be improved in the lab:  Vacuum  refurbishment of joint surfaces, new bake-out jackets, mass spectrometer  Reproducibility  New masks for microbalance thickness measurements, calibration of measurements, relative calibration of stoïchiometric ratio  Diagnostics  New control system based on VME Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Rest gas analysis by mass spectrum analyzer No conclusive result for measurement of species during deposition, but very helpful to detect leaks before coating!

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Co-Deposition Setup Isolation for each Quartz Te Cs

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Te double Coating for use CERN Optical Profiler (TS/MME) Cross-Measurement with Stylus Profiler (to arrive in December) Te Thickness Calibration Photocathodes

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Te Thickness measured with Quartz 1

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Te Thickness measured with Quartz 2 vs Quartz 1

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Te Thickness measured with Quartz 2 vs Quartz 1 1 2

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Te Thickness measured with Quartz 2 vs Quartz 1 1 2

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes Calibration will be applied along successive coatings to deduce Cs thickness from Te thickness

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes (Probe beam) Re-use of the former CTF2 equipment :  Cs-Te photocathodes produced in-situ in existing preparation chamber, adapted to the new RF-gun to be developed by collaboration LAL/CEA

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Photocathodes (Probe beam)

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Timing Drive - Probe beam 0.44  s

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Probe-beam : Preparation in situ Probe-beam RF gun Drive-beam : Transfer chamber Drive-beam RF gun Photocathodes (Probe beam)

WSHQE06, 04/10/2006R. Losito, Cs 2 Te Photocathodes for CTF3 Photoinjectors Conclusions Cs2Te Photocathodes will be produced for both Drive and Probe beams photoinjectors Drive beam:  High QE (>3%)  preparation in photocathodes lab  Effort towards control of stoichiometric ratio to improve repeatability Probe beam  Lower QE: 0.3 ÷ 0.9 %  preparation in-situ