A Method to Determine the Electric Field of Liquid Argon Time Projection Chambers Using a UV Laser System and its Application in MicroBooNE

TL;DR

This paper presents a UV laser-based method to measure and correct electric field distortions in liquid argon TPCs, demonstrated in the MicroBooNE experiment, enhancing the accuracy of neutrino detection.

Contribution

It introduces a novel in situ UV laser technique for mapping electric field distortions in liquid argon TPCs, improving detector calibration.

Findings

Successfully measured E-field distortions in MicroBooNE

Developed a method to derive spatial distortions from UV laser data

Enhanced the accuracy of neutrino measurements by correcting E-field non-uniformities

Abstract

Liquid argon time projection chambers (LArTPCs) are now a standard detector technology for making accelerator neutrino measurements, due to their high material density, precise tracking, and calorimetric capabilities. An electric field (E-field) is required in such detectors to drift ionized electrons to the anode to be collected. The E-field of a TPC is often approximated to be uniform between the anode and the cathode planes. However, significant distortions can appear from effects such as mechanical deformations, electrode failures, or the accumulation of space charge generated by cosmic rays. The latter is particularly relevant for detectors placed near the Earth's surface and with large drift distances and long drift time. To determine the E-field in situ, an ultraviolet (UV) laser system is installed in the MicroBooNE experiment at Fermi National Accelerator Laboratory. The purpose of this system is to provide precise measurements of the E-field, and to make it possible to correct for 3D spatial distortions due to E-field non-uniformities. Here we describe the methodology developed for deriving spatial distortions, the drift velocity and the E-field from UV-laser measurements.