| 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. |
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