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Abstract:
The XENON1T experiment aims at the direct detection of the well motivated dark matter
candidate of weakly interacting massive particles (WIMPs) scattering off xenon nuclei. The
first science run of 34.2 live days has already achieved the most stringent upper limit on
spin-independent WIMP-nucleon cross-sections above masses of 10GeV with a minimum
of 7:7 x 10-47cm2- at a mass of 35GeV. Crucial for this unprecedented sensitivity are a high
xenon gas purity and a good understanding of the background.
In this work, a procedure is described that was developed to measure the purity of the experiment’s
xenon inventory of more than three tons during its initial transfer to the detector gas
system. The technique of gas chromatography has been employed to analyze the noble gas
for impurities with the focus on oxygen and krypton contaminations. Furthermore, studies
on the calibration of the experiment’s dominating background induced by natural gamma
and beta radiation were performed. Hereby, the novel sources of radioactive isotopes that
can be dissolved in the xenon were employed, namely 220Rn and tritium. The sources were
analyzed in terms of a potential impact on the outcome of a dark matter search. As a result
of the promising findings for 220Rn, the source was successfully deployed in the first science
run of XENON1T. The first WIMP search of XENON1T is outlined in this thesis, in which
a background component from interactions taking place in close proximity to the detector
wall is identified, investigated and modeled. A background prediction was derived that was
incorporated into the background model of the WIMP search which was found to be in good
agreement with the observation
