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Experimental devices using patterns of holes etched into semiconductor surfaces are under evaluation for use as neutron detectors. The devices have miniature holes equidistantly spaced so as to completely cover the front surface of a planar semiconductor device. The devices have both electrical contacts and neutron-reactive coatings applied over the surface and within the holes. The tiny via holes assist in thin-film adhesion while offering a method to increase the thermal-neutron detection efficiency.

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KEYWORDSHf-based scintillator, high resolution, excellent non-proportionality, non-hygroscopic scintillator, intrinsic scintillator ABSTRACT This paper reports on successful growth and performance evaluation of two large diameter Cs2HfCl6 (CHC) and Cs2HfCl4Br2 (CHCB), both recently developed scintillator crystals. The discovery of Cs2HfCl6 (CHC) as a scintillator has lately generated much interest in this material and its family, which belongs to the K2PtCl6 cubic crystal structure. CHC is an intrinsic scintillator that is non-hygroscopic, has no self-radioactivity, provides excellent energy resolution, and has * Corresponding Author: email: drh1980@gmail.com, phone: 1-615-916-6666.2 excellent non-proportionality. CHC has a moderate density of 3.9 g/cm 3 and an effective atomic number of 58. Reported in this paper are transparent crack-free single crystal CHC and CHCB boules of one inch in diameter, both grown using the vertical Bridgman method. Samples retrieved from the boules, sized 23mm × 30mm and 23mm × 26mm, respectively, are characterized for their optical and scintillation properties. Energy resolutions of 3.5% and 3.7% (FWHM) at 662 keV, respectively, are reported. Results comparable to previously reported results for smaller crystals have been obtained. Studies on light yield, decay time, non-proportionality, as well as detector characterization are also reported.

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Tl2LiYCl6:Ce (TLYC) is a recently discovered dual mode gamma-ray and neutron scintillator. So far small crystals of this composition have been studied, but for practical applications with affordable price, large-scale crystals are required. In this work, we present successful efforts to grow crack-free single crystals with sizes up to ⌀1″ × 5.5″. A variety of experimental techniques were employed to investigate the scintillation properties. A ⌀1″ × 1.2″ TLYC cylinder has a light yield of 25,000 ph/MeV, and its energy resolution is better than 4% at 662 keV. The gamma equivalent energy (GEE) produced by thermal neutron is 1.89 MeVee, along with a neutron induced light yield of 47,000 ph/n. Pulse shape discrimination (PSD) between gamma-rays and neutrons has been successfully shown with a current Figure-of-Merit (FOM) of 2.4. This article explores the crystal growth, scintillation properties, and potential applications of TLYC.

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