Freiburg 2008 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 68: Experimentelle Methoden

T 68.8: Vortrag

Freitag, 7. März 2008, 15:50–16:05, KGI-HS 1098

Radon emanation measurements in the frame of GERDA — •Hardy Simgen and Grzegorz Zuzel — Max-Planck-Institut für Kernphysik

GERDA [1] is designed to search for neutrinoless double beta decay of Ge76. Atmospheric radioactive noble gases like Rn222 present in argon (nitrogen) and emanated from different detector components can significantly contribute to the background of the experiment. Monte Carlo simulations show that the radon concentration in argon at the level of 0.5 micro Bq/m3 (STP, proved to be achievable) would generate a background index of about 1E-4 c/kg/keV/y. Taking into account the volume of the cryostat, mentioned above concentration would correspond to the total activity of about 30 mBq. It is expected that all the other sources will not give a higher contribution, so that the expected background index remains at 1E-4 level. As potential radon sources one can consider here the steel cryostat itself, the lock with all the elements installed there (construction materials, cables, gaskets, feed-throughs) and the cryogenic infrastructure (tanks, supply lines, valves). In order to minimize the background all systems/elements being connected to the cryostat have to be tested for radon emanation and diffusion. Investigations of different type of gaskets, cryogenic valves, steel/welds, cables and other materials will be discussed. Also the emanation test of the completed inner vessel of the cryostat will be presented.

[1] I. Abt et al., GERDA Collaboration, hep-ex/0404039, http://www.mpi-hd.mpg.de/ge76/reportsLNGS/proposal_21sept.pdf