Advanced high-performance large diameter Cs2HfCl6 (CHC) and mixed halides scintillator

Abstract

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.

Novel Cs2HfCl6 Crystal Scintillator: Recent Progress and Perspectives

“…In the case of CHC4B2 crystal, the characteristic decay times were found to be 0.19 μs (11%) and 2.9 μs (89%). Hence, one could notice that while for CHC crystals of different quality the kinematics of scintillation pulse is very stable, CHC4B2 crystals still demonstrate noticeable variation in the evaluated decay components for different crystal samples (see, for comparison, values reported in [12]).…”

“…Further progress in Cs 2 HfCl 6 and Cs 2 HfCl 4 Br 2 crystals production was shown in [12]. As starting materials, CsCl (99.999%) and HfCl 4 (99.9%) for CHC, along with CsCl, CsBr (99.995%), and HfBr 4 (99.9%) for CHC4B2, were utilized.…”

“…The first CHC crystal, CHC-1, was produced from a stoichiometric mixture of as-purchased raw materials with no additional purification. Meanwhile, the second CHC crystal, CHC-2, was produced from HfCl 4 powder that underwent an improved purification by a one-fold sublimation, as described in [12]. After materials loading, each ampoule was subjected to low temperature dehydration under high vacuum to remove moisture that might be introduced during loading and subsequent steps.…”

“…The response of CHC and CHC4B2 samples to gamma irradiation was measured with the same approach, as described in [12], where studied crystal was placed into a mineral oil. The 137 Cs energy spectrum collected with a ∅10 × 15 mm 3 CHC-1 sample, showing an energy resolution of 2.8% (FWHM) at 662 keV, and light yield was measured to be 23,000 ph/MeV.…”

“…Thus, a purification stage is required. The main difference in a purification process by an improved single-fold sublimation applied here to that as described in [12,14], was in a decrease of a loaded HfCl 4 or HfBr 4 powder for a single purification run, from 200 g to 150 g. Then, for each growth, a stoichiometric mixture starting materials were loaded into quartz growth ampoules that were pre-cleaned and baked at 700 • C. Loaded ampoules were attached at the dehydration-sealing station, where the mixed materials were then dehydrated at 90 • C for a few hours, and then sealed under high vacuum. Crystal growth was performed in a two-zone vertical furnace, following thermal conditions and pulling rates as described in [12] (see above).…”