Study of electron swarm parameters in argon-based drift gases at high pressures for future neutrino experiments

• Untersuchung von Elektronschwarmparametern in argonbasierten Driftgasen bei hohen Drücken für zukünftige Neutrino Experimente

Hamacher-Baumann, Philip; Roth, Stefan (Thesis advisor); Feld, Lutz (Thesis advisor)

Aachen : RWTH Aachen University (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

Gas filled detectors have been among the first detectors used with electronic read-out in particle physics. Among them, the Time Projection Chamber has proven to be exceptionally versatile. TPCs are deployed from ultra-low background experiments, like searches for neutrino-less double-beta decays, to ultra-high multiplicity events at nuclear colliders. The TPC operation principle has been applied to various gas mixtures at pressures well below andabove atmospheric pressures and even to liquefied gases. When placed inside a magnetic field, TPCs have the ability to identify charged particles by their track curvature and characteristic energy loss. The T2K long baseline neutrino experiment utilizes three TPCs as part of their near detector to identify particles produced by ν interactions and is anticipating an upgrade with two additional TPCs. After decreasing statistical uncertainties over the accumulated T2K lifetime of over 10 years, systematics stemming from poorly understood and measured low-energetic intra-nucleon interactions are among the dominant contributions to the total uncertainty. With the recently published T2K constraint of 3σ on the CP violating phase (δCP) in the lepton sector, the reduction of systematic uncertainties have become tantamount to the success of measuring δCP to 5σ precision. Two mega-projects are currently in the construction phase to challenge the 5σ boundary: Hyper Kamiokande, Super Kamoikande’s successor in Japan, and the Deep Underground Neutrino Observatory in the US. Both rely on a better understanding of the intra-nuclear processes involved in neutrino interactions to reach their sensitivity goal. Neutrino interactions on gas components, especially hydrogen, offer a promising prospect of filling gaps in the available data for developing and improving models. DUNE aims to construct a pressurized TPC at 10 bar that could deliver this data as part of the main neutrino-oscillation physics program. The used gas mixture will be predominantly argon to provide the constraining counter-part for the liquid argon TPCs of the far detector. A proposed later-stage mixture nominates an increased content of alkanes to introduce large amounts of free protons in the form of hydrogen for clean neutrino-nucleon interactions. A miniature TPC, capable of investigating the usability of the extremes of almost pure argon and pure alkanes is desirable as a proving ground for the search of a gas mixture for a full-scale TPC of >100 m³ as for DUNE’s near detector. The performance of a TPC requires precise knowledge of the swarm parameters of free electrons in gas at varying electrical fields, pressures and temperatures. One suitable kind of miniature TPC, called Gas Monitoring Chambers, was developed for T2K at RWTH Aachen University as a continuous calibration device. This work presents the construction of a High Pressure Gas Monitoring Chamber designed for measuring the drift velocity for gas studies and calibration of a full-scale TPC at up to 10 bar. The measurement curves of the gas mixtures P2, P10 and P50 as well as the pure gases CH4, C2H6 and C3H8 are compared to the state-of-the-art simulation program MagBoltz to verify readiness for simulations in the high pressure regime following ET/p scaling.

Institutions

• Department of Physics [130000]
• Chair of Experimental Physics III B [133510]