LUX-ZEPLIN

Abstract:

We present a measurement of the cosmogenic activation in the cryogenic germanium detectors of the EDELWEISS III direct dark matter search experiment. The decay rates measured in detectors with different exposures to cosmic rays above ground are converted into production rates of different isotopes. The measured production rates in units of nuclei/kg/day are 82 ± 21 for 3H, 2.8 ± 0.6 for 49V, 4.6 ± 0.7 for 55Fe, and 106 ± 13 for 65Zn. These results are the most accurate for these isotopes. A 90% C.L. lower limit on the production rate of 68Ge of 71 nuclei/kg/day is also presented. They are compared to model predictions present in literature and to estimates calculated with the ACTIVIA code.

Abstract:

© 2017, Ivan Franko National University of Lviv. All rights reserved. The paper is devoted to the study of X-ray luminescence spectra, the scintillation light output and the decay time characterisation of undoped ZnTe at low temperatures down to 6 K. Also, the photoconductivity spectrum in a visible region has been investigated. Due to significant thermal quenching, the scintillations at α-particle excitation were detected in the sample only below T = 150 K. The emission of the crystal is attributed to the radioactive recombination of the holes trapped by Zn vacancies and electrons captured at the shallow levels of impurities or defects. The scintillation efficiency increased with further cooling. It has been found that at α-particle excitation undoped ZnTe exhibits a fairly competitive light output equal to 117 ± 20% of CaWO4reference scintillator. This finding underpins potential applications of ZnTe as a scintillation detector in the cryogenic experiments, particularly for the cryogenic search for neutrinoless double beta decay of130Te. It has been also found that ZnTe will be attractive as a conventional scintillation detector at the temperature of liquid nitrogen (T = 77 K). At this temperature, the scintillator exhibits a reasonably short decay time and a sufficient scintillation response to particle excitation. A practical implementation of this idea poses no real technical challenge since photomultipliers and Si-based photodetectors are proven to operate reliably and efficiently at this temperature.

Abstract:

It has been proven by several astronomical observations that dark matter exists, but no particle candidates have been observed yet. The CRESST experiment aims to directly detect dark matter particles elastically scattering off nuclei in CaWO4 crystals which are operated at mK temperatures. With nuclear recoil energy thresholds as low as 0.3 keV [2] and 0.6 keV [3], for the detector modules LISE and TUM40, respectively, CRESST is ideally suited for the detection of low-mass dark matter particles [5]. Additionally, the radiopurity of the crystals is another important factor for the detector performance. For a detailed understanding of the detector backgrounds, we simulate the radioactive contaminations of the TUM40 detector module with Geant4. The outcome of this simulation will be vital for the CRESST-III experiment. In this contribution, we discuss our results of the search for dark matter and dark photons achieved with the detector module Lise of CRESST-II. We will discuss the status of CRESST-III Phase 1 which started taking data in 2016.