Author: Welch, J.J.
Paper Title Page
TUAO02 Beam-Loss Detection for LCLS-II 230
  • A.S. Fisher, C.I. Clarke, B.T. Jacobson, R.A. Kadyrov, E. Rodriguez, L. Sapozhnikov, J.J. Welch
    SLAC, Menlo Park, California, USA
  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.  
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About • paper received ※ 03 September 2019       paper accepted ※ 07 September 2019       issue date ※ 10 November 2019  
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