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Abstract:
The XENON Dark Matter search is aiming for the direct detection of Dark Matter in the form
of weakly interacting massive particles (WIMPs) scattering of xenon nuclei. This process is
expected to be extremely rare, if at all existing. To be detectable, competing background has
to be suppressed to unprecedented level. This de_nes the framework for this thesis. First, the
data analysis is sketched that resulted in todays strongest limit on the spin-independent WIMPnucleon
scattering for WIMP masses above 8 GeV/c2 using an exposure of 225 live days x
34 kg collected by the Xenon100 detector. For this analysis we develop a successfully employed
consistency condition rejecting non-physical background. In the main part of this thesis, we
investigate the intrinsic backgrounds 85Kr and 222Rn. To be sensitive to a potential WIMP signal, ultra-low concentrations have to be achieved in the liquid xenon target. We developed
a method to determine krypton traces in xenon above a detection limit of only 6 parts per
quadrillion (ppq)- two orders of magnitude below previous achievements. We prove that the
cryogenic fractional distillation reaches a krypton level in xenon below 1 parts per tril (ppt).
This represents a crucial proof-of-principle for the needs of the upcoming Xenon1T detector.
Moreover, we present a 222Rn emanation assay of the Xenon100 detector and apply our results
to cast projections on the future background handling in Xenon1T. Finally, we introduce two
promising realizations of radon removal systems and argue for the utmost importance of 222Rn
emanation assays.
