Datensatz

Zusammenfassung

The currently running Xenon100 experiment and its successor, Xenon1T, use liquid xenon as target and detection material in the search for weakly interacting massive particles, a well motivated candidate for dark matter in our universe. As the expected signal rate is less than a couple of events per year, it is absolutely mandatory to understand and reduce the possible background contributions. The man-made and almost pure beta-emitter ⁸⁵Kr is a very dangerous background candidate, as krypton is intrinsically present on the ppb (parts per billion level b= 10⁻⁹) in commercially available xenon. Both further purification and the corresponding analytics are therefore equally important for these kind of experiments. This thesis describes two krypton in xenon measurement procedures and their impact on the understanding of the krypton background in the Xenon experiments. First, a mass spectroscopic set-up using gas-chromatographic pre-separation is introduced, and the improvements in terms of stability and sensitivity down to the ppq (parts per quadrillion b= 10⁻¹⁵) regime are highlighted. Subsequently several xenon assay results are presented: the evolution of the krypton concentration in Xenon100 over a time period of more than a year is reconstructed and linked to the observed radon decay rates. Furthermore, several distillation procedures are examined, showing the high potential of cryogenic distillation for xenon purification. Thereby, a measurement of ultra pure xenon with an so far unprecedented purity is presented. Finally, a second analysis method is investigated, applying a delayed coincidence analysis to the Xenon100 dark matter search data. This in-situ method is limited to the ppt (parts per trillion b= 10⁻¹²) regime, but achieves very good agreements with the mass spectroscopic results and confirms its absolute calibration.