Abstract
Application of CaMoO4 as a scintillation target in cryogenic rare event searches relies on the understanding of scintillation properties of the material at the temperatures at which these detectors operate. We devised and implemented a detection module with a low-temperature photomultiplier from Hamamatsu (model R8520-06) powered by a Cockcroft-Walton generator. The detector module containing the CaMoO4 crystal was placed in a 3He/4He dilution refrigerator and used to measure scintillation characteristics of CaMoO4 in the millikelvin temperature range. At the lowest temperature achieved, the energy resolution of CaMoO4 for 122 keV γ from a 57Co source is found to be 30%, and the fast and slow decay constants are 40.6 ± 0.8 μs and 3410 ± 50 μs, respectively. The temperature variation of the CaMoO4 decay kinetics is discussed in terms of a three-level model of the emission center.
Highlights
Interest in scintillating CaMoO4 has increased recently, driven by the prospect of application in cryogenic experiments searching for rare events [1] such as neutrinoless double beta decay (0υ2β) or dark matter particle detection
In the experiment reported here, the CaMoO4 sample was cooled to temperatures as low as 17 mK, with temperatures below 100 mK deduced from the resistance of the NTD-Ge sensor attached to the sample, using a generic calibration [22]
The ratio of the full width at half maximum (FWHM) to the peak position, which is a measure of the energy resolution of the scintillation detector, is assessed to be (18/60)×100%=30%
Summary
Interest in scintillating CaMoO4 has increased recently, driven by the prospect of application in cryogenic experiments searching for rare events [1] such as neutrinoless double beta decay (0υ2β) or dark matter particle detection Some of these experiments are based on a detector technology that involves simultaneous readout of a phonon and a light response induced by particle interaction in a scintillating target [1], [2]. Measurements involving optical excitation demonstrated that in molybdates the luminescence decay rate exhibits more than an order of magnitude increase before it reaches a constant value below 1 K This is explained by a splitting of the emission level into a pair of closely spaced sublevels [13], [14], [15], [16]. The objective of extending the characterization of CaMoO4 scintillation to the millikelvin range is twofold: the determination of scintillation efficiency and decay constant at typical operating temperatures of cryogenic phonon-scintillation detectors, and finding details of the energy structure of the emission centre in the crystal
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
