Time Evolution of Electric Fields in CDMS Detectors

TL;DR

This paper investigates how electric fields in CDMS detectors evolve over time due to radiation exposure, affecting detector performance, by modifying a Monte Carlo simulation to model the field's event-by-event changes in three dimensions.

Contribution

It introduces a modified Monte Carlo model that simulates the dynamic evolution of electric fields in CDMS detectors on an event-by-event basis in three dimensions.

Findings

Electric fields degrade with radiation exposure, impacting detector performance.

Simulation results match observed field evolution in CDMS detectors.

Understanding field evolution aids in improving detector design and operation.

Abstract

The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3" diameter x 1" thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors, the later providing a $\sim$1 V cm$^{-1}$ electric field in the detector bulk. Cumulative radiation exposure which creates $\sim 200\times 10^6$ electron-hole pairs is sufficient to produce a comparable reverse field in the detector thereby degrading the ionization channel performance. To study this, the existing CDMS detector Monte Carlo has been modified to allow for an event by event evolution of the bulk electric field, in three spatial dimensions. Our most resent results and interpretation are discussed.