Optical anisotropy and electronic structures of CdMoO4 and CdWO4 crystals: Polarized reflection measurements, x-ray photoelectron spectroscopy, and electronic structure calculations

Copyright (c) 2008 American Physical SocietyArticlePHYSICAL REVIEW B. 77(15): 155118 (2008)journal articl

Growth, Mechanical, Thermal and Spectral Properties of Cr3+∶MgMoO4 Crystal

This paper reports the growth, mechanical, thermal and spectral properties of Cr3+∶MgMoO4 crystals. The Cr3+∶MgMoO4 crystals with dimensions up to 30 mm×18 mm×14 mm were obtained by TSSG method. The absorption cross-sections of 4A2→4T1 and 4A2→4T2 transitions are 12.94×10−20 cm2 at 493 nm and 7.89×10−20 cm2 at 705 nm for E//Ng, respectively. The Cr3+∶MgMoO4 crystal shows broad band emission extending from 750 nm to 1300 nm with peak at about 705 nm. The emission cross-section with FWHM of 188 nm is 119.88×10−20 cm2 at 963 nm for E//Ng. The investigated results showed that the Cr3+∶MgMoO4 crystal may be regarded as a potential tunable laser gain medium

Scintillators for cryogenic applications: State-of-art

The latest results on the low-temperature characterisation of scintillation materials selected for rare event search are reviewed. The temperature dependences of the light output and decay time are analysed on the basis of the current understanding of the underlying physical processes that control the emission of light in solids. It is shown that scintillation properties of the materials under study are adequate for the purpose of cryogenic experiments searching for rare events. From the analysis of the performance characteristics it is concluded that currently ZnWO 4 is the most suitable scintillation target for dark matter search

The use of calcium silicate bricks for retrospective dosimetry

The suitability of calcium silicate bricks (CSBs) for the retrospective measurement of gamma dose using luminescence techniques has been investigated. Bricks of this type are distinguished from fired clay bricks by containing negligible clay and requiring comparatively low temperature treatment during manufacture. They have been used widely in the construction of buildings in the Former Soviet Union since the 1970s but hitherto have not been used for retrospective dosimetry measurements. A procedure based on the use of the 210°C thermoluminescence (TL) peak of quartz was tested with granular quartz extracted from three types of CSB, one of which had been taken from a settlement downwind of Chernobyl. The degree to which the residual geological TL signal within the temperature range of the 210°C TL peak had been reduced during manufacture varied with brick type; the levels of residual TL corresponded, in the samples tested, to absorbed doses in the range (<5 mGy–100 mGy). The TL sensitivity of the quartz was generally sufficient to measure absorbed doses of 20 mGy and above. An estimate of the cumulative fallout dose obtained with the CSB from the contaminated settlement was in good agreement with that obtained in a previous study based on measurements with a fired clay brick from the same building

The Monte-Carlo refractive index matching technique for determining the input parameters for simulation of the light collection in scintillating crystals

The Monte-Carlo refractive index matching (MCRIM) technique was developed to determine the physical properties of heavy inorganic scintillators (HIS) which are difficult to measure experimentally. It was designed as a method for obtaining input parameters for Monte-Carlo (MC) simulations of experimental arrangements incorporating HIS in their setups. The MCRIM technique is used to estimate the intrinsic light yield, the scattering coefficient and the absorption coefficient, herein referred to as indirect measurement properties. The MCRIM technique uses an experiment/MC combination to determine these indirect measurement properties. The MCRIM experimental setup comprises a crystal placed on a photomultiplier tube window with the possibility of introducing materials of different refractive indices in a small gap between the crystal and photomultiplier tube (PMT) window. The dependence of the measured light yield on the refractive index of the material in the gap can only be reproduced by simulations if the correct values of scattering, absorption and intrinsic light yield are used. The experimental setup is designed to minimise the presence of optical components such as unpolished surfaces and non-ideal reflectors, which are difficult to simulate. The MCRIM technique is tested on a 1.03×1.00×0.82 cm3 crystal of CaWO4 which is found to have a scattering coefficient of 0.061±0.005 cm-1, an absorption coefficient of 0.065±0.005 cm-1, and an intrinsic light yield of 22700±1700 photons/MeV. © 2006 Elsevier B.V. All rights reserved

Multiple photon counting coincidence (MPCC) technique for scintillator characterisation and its application to studies of CaWO4 and ZnWO4 scintillators

We describe a new method for measurements of the scintillation characteristics of crystals. The multiple photon counting coincidence (MPCC) technique involves recording the sequence of individual photon pulses resulting from a scintillation event. The timing of the individual photons allows determination of the scintillation decay time constants. The number of photons recorded per scintillation event is proportional to the scintillation light yield. The decay time constants and the relative light yield of CaWO4 and ZnWO4 scintillators have been investigated in the temperature range 9-350 K. An important advantage of the MPCC method is the possibility to reject spurious events through off-line analysis, taking into account the entire data set of scintillation events. This procedure allows cleaning of the data set from multiple scintillation events (pile-up). The MPCC technique is an excellent complement to conventional characterisation techniques and is particularly suited for investigation of slow scintillation processes. © 2005 Elsevier B.V. All rights reserved

Cryogenic scintillators for search and investigation of extremely rare events in particle physics and astrophysics

The inorganic scintillator is an important element of a new type of cryogenic phonon scintillation detectors (CPSD) developed for single particle detection. These detectors exhibiting superior energy resolution and ability to identify the type of interaction event are considered as a next generation instrumentation in the search for extremely rare events. The paper presents the latest results of our study on cryogenic scintillators thought for CPSD application in the search for dark matter. It gives a description of the concept of direct dark matter detection and the operation principles of GPSD. The paper envisages major materials requirements and summarises the results of the studies of luminescence and scintillation properties of tungstates (CaWO 4 and ZnWO4), molybdates (CaMoO4, MgMoO 4, and CdMoO4) and Ti-doped Al2O3 over a wide temperature range (9-300 K)