Analysis of the Afterpulsing and the Dark Noise Spectrum From the DEAP-3600 Detector

  • Author / Creator
    Singhrao, Kamal
  • The DEAP-3600 experiment is a 3,600 kg Liquid Argon (LAr) target scintillation detector designed to detect the Weakly Interacting Massive Particle (WIMP) dark matter candidate. The detector works by detecting photons released by nuclear recoils of Argon nuclei, using an array of 255 nearly isotropically placed photomultiplier tubes (PMTs). The detector electronics system then digitizes the pulse detected by the PMTs and is designed to maximize discrimination between single and multiple photon pulses. The data processing chain is completed with an offline processor that discriminates the dominant Ar-39 induced beta decay background from nuclear recoil induced hits pulsing pulse shaped discrimination (PSD). Each PMT has an intrinsic level of background caused by dark noise and afterpulsing that can potentially create anomalous signals in the WIMP region of interest. Dark noise is caused by photoelectrons being spontaneously emitted from the PMT photocathode material and afterpulsing is typically caused by the residual gas ions inside the PMT that drift and strike the photocathode resulting in the emission of many photoelectrons. This thesis introduces a method to characterize the levels of PMT afterpulsing and dark noise in the DEAP-3600 detector. Presented is a discussion of the implications of the resultant PMT background for the WIMP search during the detector physics data running.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.