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T: Teilchenphysik
T 409: Neutrinos III
T 409.5: Vortrag
Mittwoch, 29. März 2006, 17:20–17:35, HG2-HS7
39Ar, 85Kr and 222Rn in nitrogen for the Borexino and GERDA experiments — •Grzegorz Zuzel, Hardy Simgen, Gerd Heusser, and Stefan Schönert — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg
Borexino [1] will look for the solar neutrinos (mainly 7Be) while GERDA [2] is designed to search for neutrinoless double beta decay of 76Ge. In both experiments radioactive noble gases present in the atmosphere can significantly contribute to their background. The most important are 39Ar, 85Kr and 222Rn. They can enter the detectors through the trace amounts present in nitrogen. Nitrogen is used to remove gaseous impurities from the liquid scintillator in Borexino, and as a liquid to shield and cool the Ge crystals in GERDA. Concentrations in N2 used in Borexino must be lower than 0.5 µBq/m3 and 0.2 µBq/m3 for 39Ar and 85Kr, respectively. These limits are also sufficient for GERDA. 222Rn should be below 0.5 µBq/m3 and 7 µBq/m3 for Borexino and GERDA, respectively.
We have found such an extremely pure gas on the market and simulated the whole supply chain between a supplier and a customer, which must be kept under control. We will present sampling procedures and experimental techniques applied for the considered isotopes. Results obtained for commercially available gases, as well as tests of supply chains will be discussed.
[1] G. Alimonti et al., BOREXINO Collaboration, Astropart. Phys. 16 (2001) 205
[2] I. Abt et al., GERDA Collaboration, hep-ex/0404039