Journal
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
Volume 877, Issue -, Pages 314-322Publisher
ELSEVIER
DOI: 10.1016/j.nima.2017.09.036
Keywords
Double-beta decay; Neutrino physics; Instrumentation
Categories
Funding
- U.S. Department of Energy, Office of Science, the Office of Nuclear Physics [DEAC02-05CH11231, DE-AC52-06NA25396, DE-FG02-97ER41041, DE-FG02-97ER41033, DE-FG02-97ER41042, DE-SC0012612, DE-FG02-10ER41715, DE-SC0010254, DE-FG02-97ER41020]
- Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation [PHY-0919270, PHY-1003940, PHY-0855314, PHY-1202950, MRI 0923142, PHY-1307204, PHY-1003399]
- Russian Foundation for Basic Research [15-02-02919]
- U.S. Department of Energy through the LANL/LDRD Program
- Direct For Mathematical & Physical Scien
- Division Of Physics [1307204, 1614611] Funding Source: National Science Foundation
- U.S. Department of Energy (DOE) [DE-SC0010254] Funding Source: U.S. Department of Energy (DOE)
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The Majorana Demonstrator is an array of point-contact Ge detectors fabricated from Ge isotopically enriched to 88% in Ge-76 to search for neutrinoless double beta decay. The processing of Ge for germanium detectors is a well-known technology. However, because of the high cost of Ge enriched in Ge-76 special procedures were required to maximize the yield of detector mass and to minimize exposure to cosmic rays. These procedures include careful accounting for the material; shielding it to reduce cosmogenic generation of radioactive isotopes; and development of special reprocessing techniques for contaminated solid germanium, shavings, grindings, acid etchant and cutting fluids from detector fabrication. Processing procedures were developed that resulted in a total yield in detector mass of 70%. However, none of the acid-etch solution and only 50% of the cutting fluids from detector fabrication were reprocessed. Had they been processed, the projections for the recovery yield would be between 80% and 85%. Maximizing yield is critical to justify a possible future ton-scale experiment. A process for recovery of germanium from the acid-etch solution was developed with yield of about 90%. All material was shielded or stored underground whenever possible to minimize the formation of Ge-68 by cosmic rays, which contributes background in the double-beta decay region of interest and cannot be removed by zone refinement and crystal growth. Formation of Ge-68 was reduced by a significant factor over that in natural abundance detectors not protected from cosmic rays. (C) 2017 The Authors. Published by Elsevier B.V.
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