Dresden 2013 – wissenschaftliches Programm
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HK: Fachverband Physik der Hadronen und Kerne
HK 38: Instrumentation
HK 38.1: Vortrag
Dienstag, 5. März 2013, 14:00–14:15, WIL-C207
Insitu measurements of Krypton in Xenon gas with a quadrupole mass spectrometer following a cold-trap at a temporarily reduced pumping speed — •Ethan Brown, Stephan Rosendahl, Christian Huhmann, Hans Kettling, Martin Schlak, and Christian Weinheimer — Institut für Kernphysik, Universität Münster
Liquid xenon detectors have risen to be extremely competetive for dark matter and neutrinoless double-beta decay searches. In order to achieve the required sensitivity, backgrounds must be reduced substantially. One important background is the beta-decay of 85Kr, which constitutes a uniform internal background in liquid xenon detectors. Cryogenic distillation can be used to reduce the krypton concentration to acceptable levels, but gas diagnostics become incredibly difficult at these ultra-pure levels.
A new method for measuring the concentration of krypton in xenon has been developed, expanding on the existing technique of a cold trap and a Residual Gas Analyzer (RGA). By using a liquid nitrogen cold trap, one can take advantage of the difference in vapor pressures of krypton in xenon to freeze most of the xenon gas while allowing the krypton to pass to the measurement chamber. Here, only a few milliliters of xenon is expended in the measurement, while achieving a sensitivity of sub ppb (parts per billion). 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. This work is funded by DFG.