%0 Generic
%A Pizzella, Veronica
%C Heidelberg
%D 2021
%F heidok:30771
%R 10.11588/heidok.00030771
%T Sub-ppb xenon purity control and study of PTFE surface contamination towards the first results of XENONnT
%U https://archiv.ub.uni-heidelberg.de/volltextserver/30771/
%X The XenonnT experiment, successor of Xenon1T, aims at probing the cross sections of the interaction between a WIMP, a well-motivated dark matter candidate, and a xenon nucleus down to 1.4 × 10−48 cm2; in addition, it will allow to distinguish if the electronic event excess observed by Xenon1T was due to new physics or a new standard model background. XenonnT employs 8.5 tonnes of xenon in a dual-phase Time Projection Chamber (TPC) and it needs both ultra-pure xenon and an ultra- low background for increasing the sensitivity. Some of the impurities of concern are: radioactive impurities such as 85Kr, 222Rn and its progenies, and 3H, since they increase the background rate; electronegative impurities such as oxygen, since they reduce the amount of electrons in the TPC.  In the first part of this thesis, we present an offline purity monitor, able to detect trace impurities at sub-ppb level. The setup uses a combination of Atmospheric Pressure Ionization Mass Spectrometry (APIMS), with a commercial APIX dQ from ThermoFisher, and a custom-made gas chromatography setup. The setup is used to measure xenon samples from the start of the science run of XenonnT. First results are given on oxygen and hydrogen contamination of the gaseous phase. In the second part, a study of deposition of 222Rn daughters on Polytetrafluoroethylene (PTFE) is presented. The study was conducted in the framework of the assembly of the XenonnT TPC, as PTFE is the most abundant material. Results are given for several PTFE samples that were deployed during the Xenon1T TPC construction phase.