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Title: Uniformity measurements and new positioning algorithms for wavelength-shifting fiber neutron detectors

Wavelength-shifting (WLS) fiber scintillator detectors were successfully installed at two neutron powder diffractometers at the Spallation Neutron Source (SNS). But, they have the following second-order disadvantages: (i). they cannot have both high efficiency and images free of ghosting (position misassignment) concomitantly; (ii). the apparent detection efficiency and spatial resolution are not uniform. These issues are related to the diffusion of scintillation photons and the fluctuation in the number of photons (quantum noise) collected by photo-multiplier tubes (PMTs). Therefore, to mitigate these two issues, we developed two statistics-based positioning algorithms, i.e., a centroid algorithm (CEA) and a correlation algorithm (CA). Compared with the generally used maximum-photon algorithm (MPA), CEA eliminates the ghosting with only about a 10% loss in detection efficiency, and provides better uniformity in detection efficiency and intrinsic background. CA can effectively eliminate ghosting too, but the loss of efficiency at the group boundaries of PMTs is large. Our results indicate that both algorithms can reduce the influence of quantum noise on the neutron positioning.
Authors:
 [1] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1126976
DOE Contract Number:
AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment; Journal Volume: 751
Publisher:
Elsevier
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; wavelength-shifting fiber neutron detector; neutron diffraction; quantum noise; non-uniformity; positioning algorithm; gamma-ray sensitivity