Exploratory growth in the Li2MoO4-MoO3 system for the next crystal generation of heat-scintillation cryogenic bolometers

Abstract

International audienceIn this work, we report on the Czochralski growth of Li2MoO4 crystals up to 230 g for heat-scintillation cryogenic bolometers likely to be used in astroparticle physics and neutron spectroscopy. Their transmission properties, radiopurity levels and detector behavior characterizations were carried out in order to validate the crystal growth process. The melting characteristics, the partition coefficients of a broad range of impurities, the thermal expansion (lattice parameters and dilatometry) and specific heat properties of the crystals were measured, over a broad temperature range for the last two, providing new data likely to be used in crystal growth process numerical simulations. We also investigated the crystal growth of Li4Mo5O17 and determined its melting behavior and specific heat. The physical properties directly relevant to heat-scintillation cryogenic bolometers of Li2MoO4 and Li4Mo5O17 are discussed in the context of the current materials developed for such applications

First scintillating bolometer tests of a CLYMENE R&D on Li2MoO4 scintillators towards a large-scale dou

“…An analysis of the chemical bonding in the (110) and (001) crystallographic planes clearly shows that the latter exhibit a much lower density of chemical bonds. This is consistent with the lattice spacings in the crystal structure, the largest one being d [001] = c ≈ 9.6Å (c is a lattice parameter of the R-3 space group of the studied Li 2 MoO 4 crystal, see details in [7]), which can be viewed as a weakness at the interatomic potential level.…”

“…Particle identification parameters as light yield for γ(β)'s (LY γ(β) ) and quenching factor of light yield for α particles (QF α+t , estimated for α+triton events), as well as discrimination power (DP α+t/γ(β) ) between α+triton and γ(β) distributions are also quoted. Some results reported in [7] for the LMO-large detector have been revised. [9,10]).…”

“…This ambitious goal is going to be achieved within CLYMENE by means of both combined Czochralski pulling and modeling, Li 2 MoO 4 single crystals characterizations and exploratory bolometer tests according to well-established LUMINEU detector protocol. The present paper is devoted to the bolometric investigation of a large and a small scintillation elements produced from 230-g crystal boule, a first large-volume scintillator developed within the CLYMENE program [7]. The encouraging results detailed below unambiguously demonstrate a good starting point for the successful realization of the CLYMENE project.…”

“…Nuclide Activity (mBq/kg) Starting materials [7] Li other α radioisotopes of U/Th chains is below 0.2-0.3 mBq/kg (see Table 2). In spite of the improved energy resolution of the LMO-small detector ( Fig.…”

“…Unfortunately, we are not able to estimate the 40 K activity from the present data, because the sensitivity of aboveground bolometric measurements to the 40 K content is well above 0.01 Bq/kg due to the dominant environmental background 1 . However, according to the results of a glow-discharge mass spectrometry analysis of two samples cut just below the seed and at the end of the boule [7], the 40 K activity in the LMO-large crystal is expected to be less than 17(3) mBq/kg but no lower than 6(1) mBq/kg (about 10 mBq/kg of 40 K in the LMO-small sample due to its closer position to the seed). The 0.01 Bq/kg 40 K content is reasonable acceptable and, certainly, it can be further reduced by the purification of the starting materials and/or the boule recrystallization to be comparable to the purity level of LUMINEU enriched crystals (less than few mBq/kg of 40 K) [6].…”