Karlsruhe 2011 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 104: Niederenergie-Neutrinophysik/Suche nach dunkler Materie I
T 104.5: Vortrag
Montag, 28. März 2011, 17:50–18:05, 30.95: 121
Procurement, production and testing of BEGe detectors depleted in 76Ge — •Alexander Hegai — Kepler Center, University of Tübingen
Gerda will search for neutrinoless double beta decay with germanium detectors enriched in the isotope 76Ge (86%). To reach the expected exposure of 100 kg·y about 20 kg of new detectors of the modified Broad Energy Germanium (BEGe) type manufactured by Canberra will be produced. To demonstrate that working BEGe detectors can be produced from the procured enriched Ge material with minimised losses and no dilution, a full production-chain validation was performed. The supply chain begins with the procurement of isotopically modified Ge in the form of GeO2 from ECP, Zelenogorsk, Russia; isotopic analysis via ICPMS, NAA and PGAA; reduction and purification by zone refinement to 6Ngrade germanium at PPM, Langelsheim, Germany; further zone refining and crystal pulling at Canberra USA; and finally diode fabrication and mounting at Canberra Belgium.
The test was performed with depleted germanium , which is a by-product from the enrichment process and thus has the same chemical history and purity as the enriched Ge. Four Ge crystals were pulled, from which five detectors were manufactured. Up to now, four detectors underwent a comprehensive testing campaign to characterise their charge collection, spectroscopic and pulse-shape discrimination performance, as well as long-term stability. The performance of the detectors will be discussed.