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Title: Evaluating Beam-Loss Detectors for LCLS-2

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Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
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Report Number(s):
DOE Contract Number:
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Resource Relation:
Conference: Presented at the International Beam Instrumentation Conference (IBIC 2016) 11-15 Sep 2016. Barcelona, Spain
Country of Publication:
United States

Citation Formats

Fisher, Alan S., Field, Clive, Nicolas, Ludovic, and /SLAC. Evaluating Beam-Loss Detectors for LCLS-2. United States: N. p., 2017. Web.
Fisher, Alan S., Field, Clive, Nicolas, Ludovic, & /SLAC. Evaluating Beam-Loss Detectors for LCLS-2. United States.
Fisher, Alan S., Field, Clive, Nicolas, Ludovic, and /SLAC. Mon . "Evaluating Beam-Loss Detectors for LCLS-2". United States. doi:.
title = {Evaluating Beam-Loss Detectors for LCLS-2},
author = {Fisher, Alan S. and Field, Clive and Nicolas, Ludovic and /SLAC},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2017},
month = {Mon Mar 06 00:00:00 EST 2017}

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  • The LCLS Undulator Beam Loss Monitor System is required to detect any loss radiation seen by the FEL undulators. The undulator segments consist of permanent magnets which are very sensitive to radiation damage. The operational goal is to keep demagnetization below 0.01% over the life of the LCLS. The BLM system is designed to help achieve this goal by detecting any loss radiation and indicating a fault condition if the radiation level exceeds a certain threshold. Upon reception of this fault signal, the LCLS Machine Protection System takes appropriate action by either halting or rate limiting the beam. The BLMmore » detector consists of a PMT coupled to a Cherenkov radiator located near the upstream end of each undulator segment. There are 33 BLMs in the system, one per segment. The detectors are read out by a dedicated system that is integrated directly into the LCLS MPS. The BLM readout system provides monitoring of radiation levels, computation of integrated doses, detection of radiation excursions beyond set thresholds, fault reporting and control of BLM system functions. This paper describes the design, construction and operational performance of the BLM readout system.« less
  • The Linac Coherent Light Source (LCLS) is a SASE 1.5-15 {angstrom} x-ray Free-Electron Laser (FEL) facility. Since an ultra-short intense bunch is used in the LCLS operation one might suggest that wake fields, generated in the vacuum chamber, may have an effect on the x-ray production because these fields can change the beam particle energies thereby increasing the energy spread in a bunch. At LCLS a feedback system precisely controls the bunch energy before it enters a beam transport line after the linac. However, in the transport line and later in the undulator section the bunch energy and energy spreadmore » are not under feedback control and may change due to wake field radiation, which depends upon the bunch current or on a bunch length. The linear part of the energy spread can be compensated in the upstream linac; the energy loss in the undulator section can be compensated by varying the K-parameter of the undulators, however we need a precise knowledge of the wake fields in this part of the machine. Resistive wake fields are known and well calculated. We discuss an additional part of the wake fields, which comes from the different vacuum elements like bellows, BPMs, transitions, vacuum ports, vacuum valves and others. We use the code 'NOVO' together with analytical estimations for the wake potential calculations.« less
  • Detailed simulations were performed on beam loss rates in the vicinity of the Tevatron Collider detectors due to beam-gas nuclear elastic interactions. It turns out that this component can drive the accelerator-related background rates in the CDF and D0 detectors, exceeding those due to outscattering from collimation system, inelastic beam-gas interactions and other processes [1, 2]. Results of realistic simulations with the STRUCT and MARS codes are presented for the interaction region components and the CDF and D0 detectors. It is shown that a steel mask placed upstream of the detectors can reduce the background rates by almost an ordermore » of magnitude.« less
  • This paper reports the effect of event pileup investigated with a PET system which employs a 2-d detector-array system. Event pileup caused losses of resolution of 9%, 19.8% and 32% of the FWHM for 10, 20 and 30 mCi of positron emitter in the field of view (FOV), respectively. 9.4%, 18.7% and 28.1% of the data from the outer planes of the module were incorrectly placed in the inner planes for 5, 10, and 15 mCi of positron emitter in the FOV, respectively. A simple model of the process was formulated and was found to be adequate to describe themore » major features of event pileup for a number of source configurations and a wide range of activities.« less