Liquid xenon detector physics with XENON1T and HeXe : Electric noise stability, background discrimination studies and measurements of the scintillation pulse shape

Abstract

Liquefied xenon (LXe) is a popular detection medium for experiments searching for rare interactions proposed by beyond the Standard Model theories. It is employed in dual-phase time projection chambers (TPCs) used by experiments such as XENON1T, which attempt to measure particle dark matter interactions as well as the neutrinoless double-beta decay. A precise understanding of the processes behind the signals of such detectors is necessary to discriminate between background and signal events as well as possible. This work presents analyses regarding LXe TPCs physics. In the first part, the temporal evolution of electric noise in the XENON1T experiment is examined. Furthermore, a selection criterion, which has been developed to exclude interactions happening in the TPC’s gas phase, is extended to higher energy scales. Finally, it is investigated whether the LXe scintillation pulse shape allows to discriminate between nuclear recoils and background electronic recoils which originate from decays in or on TPC reflector panels. The pulse shape is also the topic of the second and final part. There, its electric field strength dependence is measured, using the TPC of the HeidelbergXenon (HeXe) system, for conversion electrons coming from 83mKr decays as well as for alpha-particles from decays of 222Rn and daughters.