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T: Fachverband Teilchenphysik

T 105: Experimentelle Methoden der Astroteilchenphysik 4

T 105.7: Vortrag

Donnerstag, 27. März 2014, 18:15–18:30, P7

Determination of Krypton concentration in cryogenic destilled Xenon gas with a quadrupole mass spectrometer following a cold-trap at a temporarily reduced pumping speed — •A. Fieguth, E. Brown, C. Levy-Brown, M. Murra, S. Rosendahl, S. Schneider, and C. Weinheimer — Institut für Kernphysik WWU

Liquid xenon detectors are extremly competitive for particle physics research, especially in the field of dark matter and neutrinoless beta decay search. In order to achieve the required sensitivity backgrounds must be reduced substantially. One important background is the beta-decay of ⁸⁵Kr. A method proven to be able to reduce this uniform background isotope by reducing the natural krypton concentration to the ppt-level is cryogenic distillation. At this stage gas diagonistics become difficult. A new method for measuring the concentration of Krypton in Xenon (E.Brown et al. JINST 8 (2013) P02011) has been applied to determine the efficiency of the cryogenic distillation column for the XENON1T experiment, expanding on the combined technique of a cold trap and a Residual Gas Analyzer. By using a liquid nitrogen cold trap, the difference in vapor pressue of krypton in xenon is used to freeze most of the xenon gas while allowing the krypton to pass unaffected. Here, only a few milliliters of xenon is expended in the measurement, while achieving a sensitivity of sub-ppb. The key change is the use of a butterfly valve to partially close the opening in front of the turbomolecular pump, thereby reducing the effective pumping speed and enhancing the RGA signal. Results of measurements on this distillation column will be presented. This work is funded by DFG.