3D modeling of electric fields in the LUX detector

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Published 24 November 2017 © 2017 IOP Publishing Ltd and Sissa Medialab
, , Citation D.S. Akerib et al 2017 JINST 12 P11022 DOI 10.1088/1748-0221/12/11/P11022

1748-0221/12/11/P11022

Abstract

This work details the development of a three-dimensional (3D) electric field model for the LUX detector. The detector took data to search for weakly interacting massive particles (WIMPs) during two periods. After the first period completed, a time-varying non-uniform negative charge developed in the polytetrafluoroethylene (PTFE) panels that define the radial boundary of the detector's active volume. This caused electric field variations in the detector in time, depth and azimuth, generating an electrostatic radially-inward force on electrons on their way upward to the liquid surface. To map this behavior, 3D electric field maps of the detector's active volume were generated on a monthly basis. This was done by fitting a model built in COMSOL Multiphysics to the uniformly distributed calibration data that were collected on a regular basis. The modeled average PTFE charge density increased over the course of the exposure from -3.6 to −5.5 μC/m2. From our studies, we deduce that the electric field magnitude varied locally while the mean value of the field of ∼200 V/cm remained constant throughout the exposure. As a result of this work the varying electric fields and their impact on event reconstruction and discrimination were successfully modeled.

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10.1088/1748-0221/12/11/P11022