skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Scintillating glass fiber neutron senors

Abstract

Cerium-doped lithium-silicate glass fibers have been developed at Pacific Northwest Laboratory (PNL) for use as thermal neutron detectors. By using highly-enriched {sup 6} Li , these fibers efficiently capture thermal neutrons and produce scintillation light that can be detected at the ends of the fibers. Advantages of scintillating fibers over {sup 3}He or BF{sub 3} proportional tubes include flexibility in geometric configuration, ruggedness in high-vibration environments, and less detector weight for the same neutron sensitivity. This paper describes the performance of these scintillating fibers with regard to count rates, pulse height spectra, absolute efficiencies, and neutron/gamma discrimination. Fibers with light transmission lengths (1/e) of greater than 2 m have been produced at PNL. Neutron sensors in fiber form allow development of a variety of neutron detectors packaged in previously unavailable configurations. Brief descriptions of some of the devices already produced are included to illustrate these possibilities.

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest Lab., Richland, WA (United States)
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10168344
Report Number(s):
PNL-SA-24272; CONF-940524-13
ON: DE94015213
DOE Contract Number:
AC06-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: 8. symposium on radiation measurements and applications,Ann Arbor, MI (United States),16-19 May 1994; Other Information: PBD: Apr 1994
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; GLASS SCINTILLATORS; NEUTRON DETECTION; SOLID SCINTILLATION DETECTORS; THERMAL NEUTRONS; PERFORMANCE; EFFICIENCY; 440101; GENERAL DETECTORS OR MONITORS AND RADIOMETRIC INSTRUMENTS

Citation Formats

Abel, K.H., Arthur, R.J., and Bliss, M. Scintillating glass fiber neutron senors. United States: N. p., 1994. Web.
Abel, K.H., Arthur, R.J., & Bliss, M. Scintillating glass fiber neutron senors. United States.
Abel, K.H., Arthur, R.J., and Bliss, M. 1994. "Scintillating glass fiber neutron senors". United States. doi:. https://www.osti.gov/servlets/purl/10168344.
@article{osti_10168344,
title = {Scintillating glass fiber neutron senors},
author = {Abel, K.H. and Arthur, R.J. and Bliss, M.},
abstractNote = {Cerium-doped lithium-silicate glass fibers have been developed at Pacific Northwest Laboratory (PNL) for use as thermal neutron detectors. By using highly-enriched {sup 6} Li , these fibers efficiently capture thermal neutrons and produce scintillation light that can be detected at the ends of the fibers. Advantages of scintillating fibers over {sup 3}He or BF{sub 3} proportional tubes include flexibility in geometric configuration, ruggedness in high-vibration environments, and less detector weight for the same neutron sensitivity. This paper describes the performance of these scintillating fibers with regard to count rates, pulse height spectra, absolute efficiencies, and neutron/gamma discrimination. Fibers with light transmission lengths (1/e) of greater than 2 m have been produced at PNL. Neutron sensors in fiber form allow development of a variety of neutron detectors packaged in previously unavailable configurations. Brief descriptions of some of the devices already produced are included to illustrate these possibilities.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1994,
month = 4
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • The capture and transmission of light from an event through a scintillating fiber is somewhat different than in conventional optical waveguide applications. A theoretical all-ray model that depends on surface and bulk loss factors is developed for this transmission. The capture fraction can be significantly greater than that predicted on the basis of meridional rays alone and the gross loss is nonexponential for short distances (less than or of the order of one 1/e distance). The latter phenomenon occurs because high-angle and skew rays are more rapidly attenuated than meridional rays.
  • In an optical detector such as those constructed from scintillating glass fibers, the photons represent information. This study of the flow of information in a system of devices using PNL glass fibers was undertaken in order to resolve the conflict between expected and observed peak heights. This work concentrates on the number of photons produced and the fraction of photons trapped. It is found that the number of photons produced in bulk samples of the standard glass is about one-third that expected, based on published values; there is evidence that, in fiberized glass, this may be as small as one-fifthmore » the expected value. Additionally, the fraction of trapped photons is found to be about three-fourths that expected because the glass has a smaller refractive index and the cladding a larger refractive index than published values in the spectral region of importance. These factors, taken together, are sufficient to resolve the conflict between the expected and observed peak heights. This analysis provides guidance for those who would use published materials properties to fabricate detectors in a new geometry where the materials properties may have been changed by the fabrication process.« less
  • The production and optical characterization of cerium-doped lithium silicate scintillating fibers used as thermal neutron detectors are discussed. The bulk glass continuing enriched {sup 6}Li is produced starting from high-purity commercial materials which are further purified at Pacific Northwest Laboratory (PNL). The fibers are drawn at PNL in a hot down-draw process. The fibers are coated with a silicone polymer that serves as both an optical cladding and a physical buffer coat. Optical characterization has included measurements of light output as a function of glass composition, optical attenuation lengths, and fluorescence lifetimes. Fibers have been prepared in our laboratory withmore » as-drawn attenuation lengths (l/e distance) in excess of 2 meters over sub-meter distances.« less
  • Pacific Northwest Laboratory (PNL) has fabricated cerium-activated lithium silicate scintillating fibers via a hot-downdraw process. These fibers, which, as produced, typically have a transmission length (e{sup {minus}1} length) of greater than 2 meters, are found to undergo aging when subjected to room air. The aging, which is complete in a few weeks, reduces the transmission length to the order of 0.5 meter. Because of the high alkali content of the glass (on the order of 20--30 mole % lithia), we have attributed this aging to aqueous corrosion oat the polymer cladding/glass interface. changes in transmission with chemical treatment of themore » surface support the corrosion model. Fiber transmission performance has been preserved by modifying the hot-downdraw to a double crucible to produce glass-on-glass waveguides.« less
  • Pacific Northwest Laboratory (PNL) has developed and tested the highest-transmission neutron-sensing glass fibers reported in the open literature to date. By developing glass compositions specifically for fiber drawing and by using superior oxidationstate controls and rapid quenching, PNL produces, fiber with useful lengths in excess of 200 cm. These long fibers can be used in detectors. Test results on the fibers used as a form-fitting detector around a small storage container containing neutron and gamma ray sources are reported. Excellent neutron-gamma ray discrimination has been achieved. These neutron-sensing glass optical fibers provide for new methods for monitoring the inventory of,more » preventing the diversion of, and detecting the unauthorized transport of sensitive nuclear materials. As such, it represents a significant potential element in countering the threat of nuclear terrorism.« less