Hans Kettling Universität Münster, Institut für Kernphysik

Gas analysis and purification for the XENON Project (pdf)

The XENON Project will search for Dark Matter by detecting the nuclear recoil signal induced by a Weakly Interacting Massive Particle in a 2 phase xenon time projection chamber. Interactions in the liquid phase cause scintillation and ionization signals. The electrons are drifted from the liquid into the gaseous phase and accelerated there, causing fluorescence light. Both light signals are detected by arrays of photosensitive detectors. The drift length of the electrons strongly depends on the purity of the xenon. In particular oxygen molecules reduce the electron drift length, as they absorb electrons. A SAES getter is used to remove electronegative elements in the gaseous phase. The purification systems will also comprise a distillation column in order to reduce the level of 85Kr contamination to the low ppt range. This is necessary, as beta-decay of 85Kr constitutes one of the backgrounds of the experiment. We will use 83mKr as a tracer to optimize the Xe to Kr separation.