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TY - CONF AU - Xu, H. AU - Shapiro, M.A. AU - Temkin, R.J. ED - Schaa, Volker RW ED - Power, Maria ED - Shiltsev, Vladimir ED - White, Marion TI - Dark Current Study of a Standing Wave Disk-Loaded Waveguide Structure at 17 GHz J2 - Proc. of NAPAC2016, Chicago, IL, USA, October 9-14, 2016 C1 - Chicago, IL, USA T2 - North American Particle Accelerator Conference T3 - 3 LA - english AB - We present calculations of the dark current in a high gradient accelerator with the intent of understanding its role in breakdown. The initial source of the dark current is the field emission of electrons. For a 17 GHz single-cell standing wave disk-loaded waveguide structure, the 3D particle-in-cell simulation shows that only a small portion of the charge emitted reaches the current monitors at the ends of the structure, while most of the current collides on the structure surfaces, causing secondary electron emission. In the simulation, a two-point multipactor process is observed on the side wall of the cell due to the low electric field on the surface. The multipactor approaches a steady state within nanoseconds when the electric field is suppressed by the electron cloud formed so that the average secondary electron yield is reduced. This multipactor current can cause the ionization of the metal material and surface outgassing, leading to breakdown. We report first results from an experiment designed to extract dark current directly from an accelerator cell from the side through two slits. First results show that the dark current behavior deviates from the field emission theory. PB - JACoW CP - Geneva, Switzerland SP - 971 EP - 973 KW - ion KW - electron KW - simulation KW - experiment KW - multipactoring DA - 2017/01 PY - 2017 SN - 978-3-95450-180-9 DO - 10.18429/JACoW-NAPAC2016-WEPOB31 UR - https://jacow.org/napac2016/papers/wepob31.pdf ER -