Voltage-Assisted Calorimetric Detection of Gamma Interactions in a Prototype Cryogenic Ge Detector of the EDELWEISS Collaboration for Dark Matter Search
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As a part of an R&D program to improve the sensitivity of its detectors to low-mass (\(<\)10 GeV) weakly interacting massive particles, the Edelweiss dark matter collaboration is developing cryogenic ionization-and-heat coplanar grid germanium detectors, operated in a high-bias mode where advantage is taken of the voltage-assisted amplification of the ionization signals for enhanced sensitivity to low-energy (\(<\)a few keV) interactions. First results of \(\upgamma \) calibration experiments are presented for a 200 g prototype detector, capable of sustaining collection voltages up to 180 V with a corresponding gain of 60 in the heat measurement channel for electron recoil interactions. Event populations are analyzed based on ionization and heat data and on computer modeling of the detector signals, and a tentative interpretation of the results for the heat resolution is presented, involving athermal ballistic phonon losses in the device with consequent fluctuations in the thermometer response to the energy deposit of a particle.
KeywordsDark matter Germanium cryogenic detector Neganov–Luke effect
This work has been funded in part by the P2IO LabEx (ANR-10-LABX-0038) in the framework \(\ll \) Investissements d’Avenir \(\gg \) (ANR-11-IDEX-0003-01) managed by the French National Research Agency (ANR). A.B. acknowledges the support by the DFG Excellence Initiative through the Karlsruhe School of Elementary Particle and Astroparticle Physics: Science and Technology (KSETA) as KSETA guest scientist.
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