title: ArgonCube – A Novel Concept for Liquid Argon Time Projection Chambers
Creators: name: Berner, Roman Matthias
Publisher: name: Universität Bern
Year: 2021
Subjects: subject: 530 Physics

description: Neutrinos are elementary particles that allow for the study of some of the most fundamental questions in particle physics, e.g. the matter-antimatter asymmetry observed in the Universe. Current and future neutrino experiments are designed to measure the properties of these particles with unprecedented accuracy to answer those questions. For this purpose, large data samples collected with very sensitive and precise detectors are required.

The Liquid Argon Time Projection Chamber (LArTPC) is an ideal detector for neutrino experiments as it provides accurate particle tracking and calorimetric information, and it can be scaled to large active masses for the collection of high-statistics data samples. However, monolithic LArTPCs face the problem of large cathode bias voltages of several 100 kV and a large amount of stored energy in the drift field, posing the risk of severe damage in the case of electric breakdowns. Furthermore, traditional LArTPCs employ projective wire readout systems, which introduce ambiguities in the 3-dimensional (3D) event reconstruction. The event reconstruction using data acquired with a projective wire readout is particularly challenging in high-multiplicity environments where several particle interactions can overlap within the drift window of the LArTPC.

To address these problems, the ArgonCube collaboration developed a novel LArTPC design that segments the total detector volume into several electrically and optically isolated LArTPCs sharing a common cryostat. In this way, the cathode bias voltages and the stored energies within the detector’s drift fields are reduced. Furthermore, the inactive volume of the ArgonCube detector is reduced using new technology to shape the electric field. This technology would slow down the energy released in the case of an electric breakdown.

The ArgonCube design furthermore employs a pixelated charge readout system that provides unambiguous particle tracking in 3D. In addition, a dielectric light detection system, sensitive to the Liquid Argon (LAr) scintillation light and with an excellent time resolution of O(1 ns), was developed. These detectors enable a precise association of detached energy depositions to specific neutrino interaction vertices, enabling an improved accuracy of the LArTPC event reconstruction.

This thesis motivates the use of LArTPCs in neutrino experiments and describes the novel ArgonCube concepts and technologies. Furthermore, the design and results of several prototypes used to study the performance of the ArgonCube technologies are presented. For the detector calibration, neutral pions decaying within a LArTPC can be used as standard candles. A method based on machine-learning techniques to reconstruct neutral pion decays in a modular LArTPC environment is presented.

ArgonCube found application in the Near-Detector (ND) of the Deep Underground Neutrino Experiment (DUNE) and has been proposed for one of the Far-Detector (FD) units of the experiment.