[en] Cryogenic rare event searches based on heat and light composite calorimeters have a common need for large area photon detectors with high quantum efficiency, good radiopurity and high sensitivity. By employing the Neganov–Trofimov–Luke effect, the phonon signal of particle interactions in a semiconductor absorber operated at cryogenic temperatures can be amplified by drifting the photogenerated electrons and holes in an electric field. We present here the most recent results of a Neganov–Trofimov–Luke effect light detector with an electric field configuration optimized to improve the charge collection within the absorber.

[en] For rare event searches, such as the direct dark matter search experiment CRESST (Cryogenic Rare Event Search with Superconducting Thermometers), highly sensitive temperature sensors and cryogenic detectors are indispensable. A very low energy threshold ($\ll <!--\; ???\; -->$ 100 eV) and good energy resolution is required to increase the experimental sensitivity particularly for low mass dark matter particles ($m_{DM}$ < 5 GeV/c${}^2$) and to differentiate between these rare events and other particle interactions such as, e.g., radioactive backgrounds. In this contribution we present an overview of the various facilities and techniques available at TUM which are necessary for the production, development and improvement of low temperature detectors and temperature sensors. We also explain the methods we employ for the study and characterization of such technology and the potential applications. In addition, we discuss the quality requirements imposed on the developed systems.

[en] The Physics Department of the TUM operates a shallow underground detector laboratory (UGL) in Garching, Germany. It provides $\sim <!--\; ???\; -->$ 160 m${}^2$ of laboratory space which is shielded from cosmic radiation by $\sim <!--\; ???\; -->$ 6 m of gravel and soil, corresponding to $\sim <!--\; ???\; -->$ 15 m.w.e.. The laboratory houses a cleanroom (class ISO 7) equipped for fabrication and assembly of cryogenic detectors. Furthermore, the UGL runs a ${}^3$He-${}^4$He dilution refrigerator. The infrastructure is particularly relevant for the characterization of CaWO${}_4$ target crystals for the CRESST-III experiment, detector fabrication and detector assembly for rare event searches. Future applications include detector development in the framework of coherent neutrino nucleus scattering experiments ($\mathrm{\nu <!--\; ??\; -->}$-cleus) and studying its potential as a site to search for MeV-scale Dark Matter with gram-scale cryogenic detectors.

[en] Ultra-low background experiments based on the so-called phonon-light technique (e.g., direct dark matter search experiments such as CRESST and EURECA or future experiments searching for the neutrino-less double beta decay such as CUPID) rely heavily on the sensitivity of the cryogenic light-detector at low light energies. The Neganov-Trofimov-Luke effect (NTLE) offers a promising way to increase the sensitivity of cryogenic light detectors by drifting photon induced electron-hole pairs in an electric field, thereby amplifying the heat signal in the cryogenic detector. In this contribution we present an overview and results of the current status of our detector development efforts as well as potential applications and planned future developments.

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[en] The direct dark matter search experiment CRESST uses scintillating CaWO${}_4$ single crystals as targets for possible recoils of dark matter particles. For several years these CaWO${}_4$ crystals are produced directly at TUM including the CaWO${}_4$ powder production from the raw materials CaCO${}_3$ and WO${}_3$ as well as the crystal growth via the Czochralski method. To further increase the sensitivity of the CRESST experiment, an improvement of the crystal radiopurity is crucial. To achieve this goal, a new method for the chemical purification of the raw materials has been developed at TUM. In order to investigate the radiopurity-level achieved by this method, highly-sensitive screening methods are required. In this work Accelerator Mass Spectrometry (AMS) has been tested for CaWO${}_4$ radiopurity screening and first results will be presented.

[en] CRESST (Cryogenic Rare Event Search with Superconducting Thermometers) uses CaWO_4 single crystals as targets for the direct search for dark matter particles. Since several years these CaWO_4 crystals are grown at the Technische Universitaet Muenchen. Thereby, commercially available CaCO_3 and WO_3 powders are used for the synthesis of CaWO_4 powder. For the experiment low intrinsic contaminations of the crystals play a crucial role. In order to improve the radiopurity of the crystals it is necessary to reduce potential sources for radioactive backgrounds such as U and Th. In this poster we will present our studies of the chemical purification of the CaCO_3 and CaWO_4 powders.

[en] The direct Dark Matter search experiment CRESST and the planned EURECA experiment use scintillating CaWO₄ crystals as target for Dark Matter interactions. The scintillation light is measured in a separate cryogenic detector and enables the identification of nuclear recoils based on their distinct light yield. Especially in the search for low mass Dark Matter it is therefore necessary to precisely know the Quenching Factors (QF), describing the reduction of the light yield of nuclear recoils relative to electron recoils, and their energy dependencies at low recoil energies (< 100 keV). The QFs of the target nuclei can be measured with high precision insitu at mK-temperatures with the CRESST Neutron-Scattering-Facility at the Maier-Leibnitz-Laboratory (MLL) by irradiating a dedicated cryogenic detector module with neutrons (11 MeV, from MLL accelerator). We present a new technique employed at the Neutron-Scattering-Facility as well as first promissing results. This work was supported by the DFG cluster of excellence ''Origin and Structure of the Universe'' and the MLL (Garching).

[en] There is a common need in Astroparticle experiments such as direct Dark Matter detection, neutrinoless double beta decay and coherent neutrino nucleus scattering experiments for detectors with a very low energy threshold. By employing the Neganov-Trofimov-Luke Effect (NTLE) the thermal signal of particle interactions in a semiconductor absorber, operated at cryogenic temperatures, can be amplified by drifting electrons and holes under an electric field inside the semiconductor. We present here the first results of a novel type of a NTLE light detector with a planar electric field configuration designed to improve the charge collection within the semiconductor.