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Abstract

While overwhelming evidence has been found for the existence of dark matter in
our universe, its true nature remains a mystery. The XENONnT experiment has
recently completed its commissioning and is now on the quest to solve this puzzle.
This endeavor is threatened by the background caused by the emanation of ²²²Rn.
In this work, a first estimate of the experiment’s radon concentration will be given.
Furthermore, the capabilities of the distillation-based radon removal system are
demonstrated.
For future liquid xenon (LXe) based experiments, the ²²²Rn-induced background
needs to be suppressed even further. A novel radon mitigation technique using
surface coatings has been investigated. Very promising reduction factors of more
than three orders of magnitude have been achieved with electrochemically plated
copper layers, applied to radium implanted stainless steel samples.
Additionally, the interactions of alpha particles from ²²²Rn and electrons from
^83mKr have been studied in the Heidelberg Xenon (HeXe) time projection chamber
(TPC). Field dependent measurements of the electron drift velocity as well as the
charge and light yield are presented. For both, an emphasis was put on the
regime of low drift fields, to improve the modeling and reconstruction in future
LXe detectors.