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TY - CONF AU - Hannah, A.N. AU - Conlon, J.A. AU - Dhanak, V. R. AU - Jones, L.B. AU - Lederer, S. AU - Militsyn, B.L. AU - Noakes, T.C.Q. AU - Valizadeh, R. ED - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - Metal Photocathodes Preparation for Compact Linear Accelerator at Daresbury Laboratory J2 - Proc. of IPAC2018, Vancouver, BC, Canada, April 29-May 4, 2018 C1 - Vancouver, BC, Canada T2 - International Particle Accelerator Conference T3 - 9 LA - english AB - 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. PB - JACoW Publishing CP - Geneva, Switzerland SP - 3865 EP - 3868 KW - plasma KW - cathode KW - electron KW - gun KW - laser DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-THPAL095 UR - http://jacow.org/ipac2018/papers/thpal095.pdf ER -