Elimination of ghosting artifacts from wavelength-shifting fiber neutron detectors

Journal Article · Tue Jan 15 00:00:00 EST 2013 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4789497· OSTI ID:22105354

Wang, C. L.; Diawara, Y.; Hannan, B. W.; Hodges, J. P. ^[1]; Clonts, L. G. ^[2]

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1. Instrument and Source Design Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
2. Research Accelerator Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

Misassignment of neutron position (ghosting) produces artifacts which have been observed in wavelength-shifting (WLS) fiber detectors developed for time-of-flight (TOF) neutron powder diffraction. In position-sensitive detectors (PSDs) with WLS fiber encoding, thermal and cold neutrons interact with a monolithic {sup 6}LiF/ZnS:Ag scintillator screen, and scintillation photons are generated and transported through the crossed fibers to photomultipliers (PMTs). The neutron position is determined by photon counts in the PMTs within a preset time window. Ghosting occurs when neutrons hit the group boundaries of two neighboring PMTs for x-position multiplexing, which is modeled as resulting from a long travel length (about 3-5 mm) of a small number of scintillation photons. This model is supported by the change observed in aperture images when the threshold number for photon-pulses was adjusted for neutron event determination. When the threshold number of photon-pulses was set above 10 for each PMT, the ghost peaks in the aperture images and TOF spectra of powder diffraction were strongly suppressed or completely eliminated, and the intrinsic background levels of the WLS detectors were significantly reduced. Our result indicates that WLS fiber detector is a promising alternative for {sup 3}He PSDs for neutron scattering.

• OSTI ID: 22105354
• Journal Information: Review of Scientific Instruments, Vol. 84, Issue 1; Other Information: (c) 2013 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
COLD NEUTRONS
FIBERS
HELIUM 3
IMAGES
NEUTRON DETECTION
NEUTRON DETECTORS
NEUTRON DIFFRACTION
PHOTOMULTIPLIERS
PHOTONS
POSITION SENSITIVE DETECTORS
SCINTILLATIONS
SOLID SCINTILLATION DETECTORS
TIME-OF-FLIGHT METHOD
WAVELENGTHS
ZINC SULFIDES