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TY - CONF AU - Fisher, A.S. AU - Clarke, C.I. AU - Jacobson, B.T. AU - Kadyrov, R.A. AU - Rodriguez, E. AU - Sapozhnikov, L. AU - Welch, J.J. ED - Schaa, Volker RW ED - Jansson, Andreas ED - Shea, Thomas ED - Olander, Johan TI - Beam-Loss Detection for LCLS-II J2 - Proc. of IBIC2019, Malmö, Sweden, 08-12 September 2019 CY - Malmö, Sweden T2 - International Beam Instrumentation Conferenc T3 - 8 LA - english AB - SLAC is now installing LCLS-II, a superconducting electron linac driven by continuous RF at 1.3 GHz. The 4-GeV, 120-kW beam has a maximum rate of nearly 1 MHz and can be switched pulse-by-pulse to either of two undulators, to generate hard and soft x rays. Two detector types measure beam losses. Point beam-loss monitors (PBLMs) set limits at critical loss points: septa, beam stoppers and dumps, halo collimators, protection collimators (which normally receive no loss), and zones with weak shielding. PBLMs are generally single-crystal diamond detectors, except at the gun, where a scintillator on a PMT is more sensitive to the low-energy (1 MeV) beam. Long beam-loss monitors (LBLMs) use 200-m lengths of radiation-hard optical fiber, each coupled to a PMT, to capture Cherenkov light from loss showers. LBLMs protect the entire 4-km path from gun to beam dump and locate loss points. In most regions two fibers provide redundancy and view the beam from different angles. Loss signals are integrated with a 500-ms time constant and compared to a threshold; if exceeded, the beam is stopped within 0.2 ms. We report on our extensive tests of the detectors and the front-end signal processing. PB - JACoW Publishing CP - Geneva, Switzerland SP - 229 EP - 232 KW - radiation KW - detector KW - linac KW - gun KW - electron DA - 2019/11 PY - 2019 SN - 2673-5350 SN - 978-3-95450-204-2 DO - doi:10.18429/JACoW-IBIC2019-TUAO02 UR - http://jacow.org/ibic2019/papers/tuao02.pdf ER -