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TY - CONF AU - Wisniewski, E.E. AU - Conde, M.E. AU - Doran, D.S. AU - Gai, W. AU - Gao, Q. AU - Ha, G. AU - Halavanau, A. AU - Liu, W. AU - Piot, P. AU - Power, J.G. AU - Whiteford, C. ED - Koscielniak, Shane ED - Satogata, Todd ED - Schaa, Volker RW ED - Thomson, Jana TI - Demonstration of Fast, Single-shot Photocathode QE Mapping Method Using MLA Pattern Beam 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 - Quantum efficiency (QE) is the chief figure of merit in the characterization of photocathodes. Semiconductor photocathodes, especially when used in high rep-rate photo-injectors, are known to show QE degradation over time and must be replaced. The total QE is the basic diagnostic which is used widely and is easy to obtain. However, a QE map indicating variations of QE across the cathode surface has greater utility. It can quickly diagnose problems of QE inhomogeneity. Most QE mapping techniques require hours to complete and are thus disruptive to a user facility schedule. A fast, single-shot method has been proposed (citation) using a micro-lens array (MLA) generated QE map. In this paper we report the implementation of the method at Argonne Wakefield Accelerator facility. A micro-lens array (MLA) is used to project an array of beamlets onto the photocathode. The resulting photoelectron beam in the form of an array of electron beamlets is imaged at a YAG screen. Four synchronized measurements are made and the results used to produce a QE map of the photocathode. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1293 EP - 1295 KW - laser KW - cathode KW - electron KW - gun KW - optics DA - 2018/06 PY - 2018 SN - 978-3-95450-184-7 DO - 10.18429/JACoW-IPAC2018-TUPMF020 UR - http://jacow.org/ipac2018/papers/tupmf020.pdf ER -