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TY - CONF AU - Jones, L.B. AU - Militsyn, B.L. AU - Noakes, T.C.Q. AU - Scheibler, H.E. AU - Terekhov, A.S. ED - Henderson, Stuart ED - Akers, Evelyn ED - Satogata, Todd ED - Schaa, Volker R.W. TI - The Evolution of the Transverse Energy Distribution of Electrons from a GaAs Photocathode as a Function of its Degradation State J2 - Proc. of IPAC2015, Richmond, VA, USA, May 3-8, 2015 C1 - Richmond, VA, USA T2 - International Particle Accelerator Conference T3 - 6 LA - english AB - The brightness of a photoelectron injector is fundamentally limited by the mean longitudinal and transverse energy distributions of the photoelectrons emitted from its photocathode, and is increased significantly if the mean values of these quantities are reduced. To address this, ASTeC constructed a Transverse Energy Spread Spectrometer (TESS)* – an experimental facility designed to measure these transverse and longitudinal energy distributions which can be used for III-V semiconductor, alkali antimonide/telluride and metal photocathode research. We present measurements showing evolution of the transverse energy distribution of electrons from GaAs photocathodes as a function of their degradation state. Photocathodes were activated to negative electron affinity in our photocathode preparation facility (PPF)** with quantum efficiency around 10.5%. They were then transferred to TESS under XHV conditions, and progressively degraded through controlled exposure to oxygen. Data has been collected under photocathode illumination at 635 nm, and demonstrates a constant relationship between energy distribution and the level of electron affinity. PB - JACoW CP - Geneva, Switzerland SP - 1748 EP - 1751 KW - electron KW - detector KW - cathode KW - brightness KW - vacuum DA - 2015/06 PY - 2015 SN - 978-3-95450-168-7 DO - 10.18429/JACoW-IPAC2015-TUPJE055 UR - http://jacow.org/ipac2015/papers/tupje055.pdf ER -