Signals induced by charge-trapping in EDELWEISS FID detectors: analytical modeling and applications

TL;DR

This paper develops an analytical model for signals caused by charge-trapping in EDELWEISS-III FID detectors, enabling improved event characterization, energy correction, and baseline resolution in dark matter searches.

Contribution

It introduces a novel analytical model based on the Shockley-Ramo theorem for charge-trapping signals in FID detectors, enhancing detector calibration and data analysis.

Findings

Veto electrodes can determine event depth and charge trapping.

Model improves heat and ionization energy corrections.

Application to real data enhances detector performance.

Abstract

The EDELWEISS-III direct dark matter search experiment uses cryogenic HP-Ge detectors Fully covered with Inter-Digitized electrodes (FID). They are operated at low fields ($<1\;\mathrm{V/cm}$), and as a consequence charge-carrier trapping significantly affects both the ionization and heat energy measurements. This paper describes an analytical model of the signals induced by trapped charges in FID detectors based on the Shockley-Ramo theorem. It is used to demonstrate that veto electrodes, initially designed for the sole purpose of surface event rejection, can be used to provide a sensitivity to the depth of the energy deposits, characterize the trapping in the crystals, perform heat and ionization energy corrections and improve the ionization baseline resolutions. These procedures are applied successfully to actual data.