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Title: Higher resolution alkali halide scintillators

  1. Radiation Monitoring Devices, Inc., Watertown, MA (United States)
Publication Date:
Research Org.:
Radiation Monitoring Devices, Inc., Watertown, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Type / Phase:
Resource Type:
Technical Report
Country of Publication:
United States
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 61 RADIATION PROTECTION AND DOSIMETRY; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 62 RADIOLOGY AND NUCLEAR MEDICINE; Scintillator; alkali halides; CsI; co-doping; non-proportionality; energy resolution; gamma-ray; radiation detectors

Citation Formats

Glodo, Jaroslaw. Higher resolution alkali halide scintillators. United States: N. p., 2017. Web.
Glodo, Jaroslaw. Higher resolution alkali halide scintillators. United States.
Glodo, Jaroslaw. Mon . "Higher resolution alkali halide scintillators". United States. doi:.
title = {Higher resolution alkali halide scintillators},
author = {Glodo, Jaroslaw},
abstractNote = {},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Mar 27 00:00:00 EDT 2017},
month = {Mon Mar 27 00:00:00 EDT 2017}

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  • An ideal 3He detector replacement for the near- to medium-term future will use materials that are easy to produce and well understood, while maintaining thermal neutron detection efficiency and gamma rejection close to the 3He standard. Toward this end, we investigated the use of standard alkali halide scintillators interfaced with 6Li and read out with photomultiplier tubes (PMTs). Thermal neutrons are captured on 6Li with high efficiency, emitting high-energy and triton ( 3H) reaction products. These particles deposit energy in the scintillator, providing a thermal neutron signal; discrimination against gamma interactions is possible via pulse shape discrimination (PSD), since heavymore » particles produce faster pulses in alkali halide crystals. We constructed and tested two classes of detectors based on this concept. In one case 6Li is used as a dopant in polycrystalline NaI; in the other case a thin Li foil is used as a conversion layer. In the configurations studied here, these systems are sensitive to both gamma and neutron radiation, with discrimination between the two and good energy resolution for gamma spectroscopy. We present results from our investigations, including measurements of the neutron efficiency and gamma rejection for the two detector types. We also show a comparison with Cs 2LiYCl 6:Ce (CLYC), which is emerging as the standard scintillator for simultaneous gamma and thermal neutron detection, and also allows PSD. We conclude that 6Li foil with CsI scintillating crystals has near-term promise as a thermal neutron detector in applications previously dominated by 3He detectors. The other approach, 6Li-doped alkali halides, has some potential, but require more work to understand material properties and improve fabrication processes.« less
  • Proton and gamma-rap responses of the alkali halide scintillators, NaI KI, CSI,LiI and Li/syp 6/I were obtained and the response of a 5-Mev proton was found to be approximately equivalent to the response of a 7-Mev electron for all five scintillators. Special emphasis was given to the responses of LiI and Li/ sup 6/I in ana attempt to clarify various anomalies which arose in the course of neutron energy measurements with LiI by means of the Li/sup 6/(n, alpha ) reaction. From an estimate of the triton response of LiI and Li/sup 6/I, which was derived from the proton andmore » gamma-ray data in confunction with the alpha- particle response and measurements of the pulse height of the Li/sup 6/(n, alpha ) group, it was shown that energy calibration of the Li/sup 6/(n, alpha ) group with gamma rays is unsatisfactory. (auth)« less
  • A study of the reduction of uranium(III) chloride, in solution in molten KCl-AlCl/sub 3/ mixtures, by molten aluminum was extended to include the effect of substitution of Na/sup +/ or Cs/sup +/ for K/sup +/ and of Br/sup -/ for all, or part, of the Cl/sup -/. Substitution of Na/sup +/ for K/sup +/ hinders the reduction of uranium chloride whereas substitution of Cs/sup +/ for K/sup +/ enhanced the reduction. The effect is in the direction anticipated in view of the relative chioride donor strengths of these alkali chlorides. The reduction of urinium bromide by Al in the systemmore » KBr-AlBr/sub 4/--Al occurs to a lesser extent than in the analogous chloride system. On the other hand. substitution of from 5 to l0 mole percent of the chloride by bromide results in markedly enhanced reduction. These results are expiained in terms of the relative strengths of the AlCl/sub 4/ and AlBr/sub 4/ complexes and the reiative stabilities of UCl/sub 3/ and UBr/sub 3/. (auth)« less
  • This project uses advanced ceramic processes to fabricate large, optical-quality, polycrystalline lanthanum halide scintillators to replace small single crystals produced by the conventional Bridgman growth method. The new approach not only removes the size constraint imposed by the growth method, but also offers the potential advantages of both reducing manufacturing cost and increasing production rate. The project goal is to fabricate dense lanthanum halide ceramics with a preferred crystal orientation by applying texture engineering and solid-state conversion to reduce the thermal mechanical stress in the ceramic and minimize scintillation light scattering at grain boundaries. Ultimately, this method could deliver themore » sought-after high sensitivity and <3% energy resolution at 662 keV of lanthanum halide scintillators and unleash their full potential for advanced gamma ray detection, enabling rapid identification of radioactive materials in a variety of practical applications. This report documents processing details from powder synthesis, seed particle growth, to final densification and texture development of cerium doped lanthanum bromide (LaBr{sub 3}:Ce{sup +3}) ceramics. This investigation demonstrated that: (1) A rapid, flexible, cost efficient synthesis method of anhydrous lanthanum halides and their solid solutions was developed. Several batches of ultrafine LaBr{sub 3}:Ce{sup +3} powder, free of oxyhalide, were produced by a rigorously controlled process. (2) Micron size ({approx} 5 {micro}m), platelet shape LaBr{sub 3} seed particles of high purity can be synthesized by a vapor phase transport process. (3) High aspect-ratio seed particles can be effectively aligned in the shear direction in the ceramic matrix, using a rotational shear-forming process. (4) Small size, highly translucent LaBr{sub 3} (0.25-inch diameter, 0.08-inch thick) samples were successfully fabricated by the equal channel angular consolidation process. (5) Large size, high density, translucent LaBr{sub 3} ceramics samples (3-inch diameter, > 1/8-inch thick) were fabricated by hot pressing, demonstrating the superior manufacturability of the ceramic approach over single crystal growth methods in terms of size capability and cost. (6) Despite all these advances, evidence has shown that LaBr{sub 3} is thermally unstable at temperatures required for the densification process. This is particularly true for material near the surface where lattice defects and color centers can be created as bromine becomes volatile at high temperatures. Consequently, after densification these samples made using chemically prepared ultrafine powders turned black. An additional thermal treatment in a flowing bromine condition proved able to reduce the darkness of the surface layer for these densified samples. These observations demonstrated that although finer ceramic powders are desirable for densification due to a stronger driving force from their large surface areas, the same desirable factor can lead to lattice defects and color centers when these powders are densified at higher temperatures where material near the surface becomes thermally unstable.« less