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PHIN tests at CTF

PHIN tests at CTF. C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev CLIC meeting 13.01.2012, CERN. Outline. Introduction NEG activation in PHIN gun Results from PHIN run in September 2011 Comparison with results from previous PHIN run Outlook. PHIN Photoinjector and CTF3.

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PHIN tests at CTF

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  1. PHIN tests at CTF C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev CLIC meeting 13.01.2012, CERN

  2. Outline • Introduction • NEG activation in PHIN gun • Results from PHIN run in September 2011 • Comparison with results from previous PHIN run • Outlook C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  3. PHIN Photoinjector and CTF3 FCT: Fast current transformerVM: Vacuum mirror SM: Steering magnet BPM: Beam position monitorMSM: Multi-slit Mask OTR: Optical transition radiation screen MTV: Gated cameras SD: Segmented dump FC: Faraday cup C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  4. Laser System Harmonics To future CALIFES laser Cooling 3.6kW 4.67mJ in 1.2μs 1.5 GHz Synched oscillator Cw pre-amplifier 10W Booster amplifier 320mW 3-pass amplifier 3.5kW 2-pass amplifier 8.3kW 2ω 4ω 7.8kW 14.8mJ in 1.2μs Harmonics test stand 1.25kW 1.5mJ in 1.2μs HighQ front end AMP1 and AMP2 To PHIN C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  5. PHIN and CLIC Parameters One main issue is to achieve long lifetimes with high bunch charge and long trains! C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  6. Improvement of Vacuum • From the experience with DC guns it is known that long cathode lifetimes are possible in case of excellent vacuum conditions: • Aim: To improve the vacuum conditions in PHIN to achieve longer cathode lifetimes. • Possible solution: Using state-of-the-art NEG pumps and coatings. p < 1e-10 mbar G. Suberlucq C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  7. Activation of NEG Chamber in PHIN Layout PHIN gun: Plan to improve vacuum in two steps: • Activation of existing NEG coated chamber around the gun • Activation of existing NEG coating in beam line and installation of additional NEG pump. Laser beam Electron beam Photo cathode 20 cm C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  8. NEG Activation Cycle Bake-out cycle: Pressure evolution: Effect of the NEG pumping C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  9. Results of NEG Activation Layout PHIN gun: Results: • Before bake-out: PBA=1.8e-10 mbar PPenning=5.2e-11 mbar • After bake-out: PBA=1.3e-10 mbarPPenning=3.3e-11 mbar • RGA spectrum: PBA PPenning C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  10. PHIN Run September 2011 • High bunch charge production. • Study of the impact of the bunch charge and train length on the vacuum level. • Lifetime measurements with comparable conditions as during the PHIN run in March 2011. • Lifetime measurements with long bunch trains. • Two Cs2Te cathodes were used: • #182 (already in use during PHIN run in March 2011) • #185 (new cathode) C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  11. High Charge Production • Charge vs. laser energy scan with 50 ns long trains • Linear response up to 5 nC • Record bunch charge of 9.2 nC above CLIC requirements! • Close to the theoretical limit of Qmax=9.47 nC for a beam size of 1.8 mm s x 1.25 mm s 9.2 nC! Cathode #185 Cs2Te C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  12. Impact of Bunch Charge on Vacuum Vacuum vs. bunch charge • Vacuum can be maintained up to nominal bunch charge of PHIN of 2.3nC. • Pressure increase above nominal bunch charge probably due to losses inside gun. • A 1 GHz gun specially designed for CLIC might be able to maintain the vacuum up to a higher bunch charge due to larger apertures. C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  13. Impact of Train Length on Vacuum Corresponding beam losses Between FCT and Faraday cup Vacuum vs. train-length • Vacuum correlated to beam losses in the beam line • When beam is optimized for good transport, the vacuum can be maintained with increasing trainlength C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  14. Data Acquisition System for Lifetime Measurements • Matlab program for automated QE measurements: • Energy of reflected laser beam from viewport (laser probe with sampler) • Charge (FCT with sampler) • Manual measurements: • Full laser beam energy in CTF2 (laser probe with flipping mirror and sampler) • Full laser beam energy in laser lab (energy meter) • Charge (FCT, Faraday cup with oscilloscope) • Automated measurement of the vacuum level C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  15. Automated QE Measurement C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  16. Automated QE Measurement  Drift of some (which?) equipment with 24 h period. C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  17. Lifetime Studies of Cs2Te Cathodes • Cathode lifetime vs. vacuum • Correlation between lifetime and vacuum. • In high e-9 mbar/ low e-8 mbar < 50h lifetime was measured. • When vacuum is kept at low e-9 mbar lifetime is within specification. Cathode #182 C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  18. Lifetime Studies of Cs2Te Cathodes • New cathode, first hours with short trains (2.3 nC, 350 ns) • Vacuum of ~1.6e-9 mbar. • Long lifetime within specifications. • Conditions (except vacuum) comparable with measurements during PHIN run in February/March before the NEG activation Cathode #185 C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  19. Long Bunch Trains Cathode #185 Cathode #185 • Measurements were performed towards the end of the PHIN run with non-optimal vacuum conditions (6e-9 mbar). • No overnight measurements possible due to 4th harmonics crystal degradation. C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  20. Comparison with Short Trains Cathode #185 Cathode #185  Similar results for short trains at the end of the run with the same vacuum conditions (6e-9mbar). C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  21. Comparison with Results from PHIN Run February/March 2011 September 2011 • Vacuum was better during PHIN run in September. • Much less breakdowns. • The lifetime was significantly better: e.g. for 2.3 nC and 350 ns30 h vs. 250 h Cathode #182 C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  22. Summary and Outlook • NEG coating in PHIN gun successfully activated. • Systematic lifetime studies vs. bunch charge, train length and vacuum carried out at PHIN. • Record bunch charge of 9.2 nC measured. • Lifetime studies of Cs3Sb cathodes with green light planned for the next PHIN run in March 2012. • Further improvement of vacuum in PHIN planned for the PHIN run thereafter (installation of NEG pump, activation of NEG coating in beam pipe). • Installation of new laser system for CALIFES photoinjector planned for winter shutdown. C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

  23. Roadmap C. Hessler, E. Chevallay, M. Csatari, S. Doebert, V. Fedosseev

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