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Persistent URL http://purl.org/net/epubs/work/39596257
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Record Id 39596257
Title Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory
Abstract The photoinjector of the CLARA FEL test facility Front End at Daresbury Laboratory is based on a S-band 10 Hz photocathode RF-gun operating with a copper photocath-ode which is driven by the third harmonic of a Ti:Sapphire laser (266 nm). The main aim of this study was to establish a procedure to prepare the Cu surface prior to installation so a Quantum Efficiency (QE) of 10-5 or higher can be achieved at laser power density below the ablation threshold of copper. The best results have been obtained by ex-situ chemical cleaning. This removed the surface oxide layer whilst at the same time producing a surface buffer layer. This inhibited the regrowth of native oxide for up to a week when exposed to normal ambient atmospheric conditions. With either chemical cleaning or Ar plasma cleaning after heating the sample in-situ to 150 °C for 90 minutes or 250 °C for 40 hours, almost all of the surface oxide was removed. For these surfaces a QE of 4.10-5 or better was measured. Oxygen plasma cleaning at 100% and 20% power produced CuO layer with surface carbon contaminant to 3 atomic %, however in-situ thermal cycling resulted in at best a QE of 3·10-6.
Organisation ASTeC , STFC
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Language English (EN)
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Paper In Conference Proceedings In 9th International Particle Accelerator Conference (IPAC18), Vancouver, Canada, 29 Apr 2018 - 4 May 2018, (2018): 3865-3868. http://accelconf.…/papers/thpal095.pdf 2018