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TY - CONF AU - Lagotzky, S. AU - Calatroni, S. AU - Muranaka, T. AU - Müller, G. AU - Serbun, P. ED - Petit-Jean-Genaz, Christine ED - Arduini, Gianluigi ED - Michel, Peter ED - Schaa, Volker RW TI - Enhanced Field Emission and Emitter Activation on Flat Dry-ice Cleaned Cu Samples J2 - Proc. of IPAC2014, Dresden, Germany, June 15-20, 2014 C1 - Dresden, Germany T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Enhanced field emission (EFE), resulting in dark currents and electric breakdowns, is one of the main gradient limitations for the CLIC accelerating structures (actual design Eacc = 100 MV/m, Epeak = 240 MV/m *). Measurements on diamond-turned, flat (Ra = 158 nm) Cu samples showed first EFE at surface fields Es = 130 MV/m. In order to reduce EFE, we have installed a commercial dry ice cleaning (DIC) system in a clean room environment (class iso 5). Accordingly, the number density of emitters (N) was significantly decreased by DIC from N = 52 /cm² to N = 12 /cm² at Es = 190 MV/m. Furthermore we have tested two diamond-turned and chemically etched (SLAC treatment, Ra = 150 nm) Cu samples after DIC resulting in EFE onset at 230 MV/m. Locally measured I(V) curves of the strongest emitters yielded field enhancement factors b = 10 – 90 (10 – 85) on the diamond-turned (chemically etched), respectively. SEM and EDX investigations of the located emission sites revealed surface defects and few particulates (Al, Ca, Si) as origin of the EFE. Moreover, strong emitter activation effects were observed. A possible breakdown mechanism based on this EFE activation will be discussed. PB - JACoW CP - Geneva, Switzerland SP - 2261 EP - 2263 KW - site KW - electron KW - vacuum KW - factory KW - gun DA - 2014/07 PY - 2014 SN - 978-3-95450-132-8 DO - 10.18429/JACoW-IPAC2014-WEPME005 UR - http://jacow.org/ipac2014/papers/wepme005.pdf ER -