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TY - CONF AU - Jones, L.B. AU - Bakin, V.V. AU - Militsyn, B.L. AU - Noakes, T.C.Q. AU - Scheibler, H.E. AU - Terekhov, A.S. ED - Belomestnykh, Sergey ED - Hoffman, Caitlin M. ED - Schaa, Volker RW TI - GaAs Photocathode R&D: Energy Spread Measurements and the Nature of the Activated p-GaAs(Cs, O) Activation Layer J2 - Proc. of ERL2015, Stony Brook, NY, USA, June 7-12, 2015 C1 - Stony Brook, NY, USA T2 - ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs T3 - 56 LA - english AB - Electron injector brightness is limited by the energy spread in the electrons emitted from a photocathode. Knowledge and understanding of the physical mechanisms underpinning this energy spread is critical in the development of high-performance electron sources, as is the ability to quantify this energy spread. In order to measure longitudinal and transverse photoelectron energy distribution curves, ASTeC, in collaboration with the ISP, have developed a Transverse Energy Spread Spectrometer (TESS) which permits measurement of photoelectron energy spread for different photocathode types under varying conditions of degradation, temperature and illumination. We describe the operating principle of this equipment. Photocathode performance is strongly affected by surface structure, with stoichiometry and roughness playing key roles in defining electron energy spread. A complete understanding of the nature of the activated GaAs surface has not yet been achieved, but it is known that the nature of the activation layer is dependent on the layer thickness. We present work which shows the transition point between the dipole layer model and the heterojunction layer model in (Cs, O) films. PB - JACoW CP - Geneva, Switzerland SP - 97 EP - 96 DA - 2015/09 PY - 2015 SN - 978-3-95450-183-0 DO - 10.18429/JACoW-ERL2015-THIALH2072 UR - http://jacow.org/ERL2015/papers/thialh2072.pdf ER -