A detector module with highly efficient surface-alpha event rejection operated in CRESST-II Phase 2

Abstract

The cryogenic dark matter experiment CRESST-II aims at the direct detection of WIMPs via elastic scattering off nuclei in scintillating CaWO${}_4$ crystals. We present a new, highly improved, detector design installed in the current run of CRESST-II Phase 2 with an efficient active rejection of surface-alpha backgrounds. Using CaWO${}_4$ sticks instead of metal clamps to hold the target crystal, a detector housing with fully-scintillating inner surface could be realized. The presented detector (TUM40) provides an excellent threshold of $\sim 0.60$keV and a resolution of $\sigma \approx 0.090$ keV (at 2.60keV). With significantly reduced background levels, TUM40 sets stringent limits on the spin-independent WIMP-nucleon scattering cross section and probes a new region of parameter space for WIMP masses below 3GeV/c${}^2$. In this paper, we discuss the novel detector design and the surface-alpha event rejection in detail.

9 pages, 6 figures

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• Direct Detection of Dark Matter -- APPEC Committee Report
• A prototype detector for the CRESST-III low-mass dark matter search
• A CsI low temperature detector for dark matter search
• Dark-Photon Search using Data from CRESST-II Phase 2
• Limits on Interactions between Weakly Interacting Massive Particles and Nucleons Obtained with NaI(Tl) crystal Detectors
• Phonon and light read out of a Li${}_2$MoO${}_4$ crystal with multiplexed kinetic inductance detectors
• Depth profile study of ${}^{210}$Pb in the surface of an NaI(Tl) crystal
• A Study of NaI(Tl) crystal Encapsulation using Organic scintillators for the Dark Matter Search
• Measurement of low-energy background events due to ${}^{222}$Rn contamination on the surface of a NaI(Tl) crystal