Background studies for NaI(Tl) detectors in the ANAIS dark matter project

Journal Article · Thu Aug 08 00:00:00 EDT 2013 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4818100· OSTI ID:22218172

Amaré, J.; Borjabad, S.; Cebrián, S.; Cuesta, C.; Fortuño, D.; García, E.; Ginestra, C.; Gómez, H.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; Solórzano, A. Ortiz de; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P. ^[1]

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1. Laboratorio de Física Nuclear y Astropartículas, Universidad de Zaragoza, Calle Pedro Cerbuna 12, 50009 Zaragoza, Spain and Laboratorio Subterráneo de Canfranc, Paseo de los Ayerbe s/n, 22880 Canfranc Estación, Huesca (Spain)

Several large NaI(Tl) detectors, produced by different companies, have been operated in the Canfranc Underground Laboratory (LSC) in the frame of the ANAIS (Annual modulation with NaI Scintillators) project devoted to the direct detection of dark matter. A complete background model has been developed for a 9.6 kg detector (referred as ANAIS-0 prototype) after a long data taking at LSC. Activities from the natural chains of {sup 238}U and {sup 232}Th, and {sup 40}K in the NaI(Tl) crystal were evaluated applying different methods: discrimination of alpha particles vs beta/gamma background by Pulse Shape Analysis for quantifying the content of the natural chains and coincidence techniques for {sup 40}K. Radioactive contaminations in the detector and shielding components were also determined by HPGe spectrometry. Monte Carlo simulations using Geant4 package were carried out to evaluate their contribution. At high energies, most of the measured background is nicely reproduced; at low energy some non-explained components are still present, although some plausible background sources have been analyzed. The {sup 40}K content of the NaI(Tl) crystal has been confirmed to be the dominant contributor to the measured background with this detector. In addition, preliminary results of the background characterization, presently underway at the LSC, of two recently produced NaI(Tl) detectors, with 12.5 kg mass each, will be presented: cosmogenic induced activity has been clearly observed and is being quantified, and {sup 40}K activity at a level ten times lower than in ANAIS-0 has been determined.

• OSTI ID: 22218172
• Journal Information: AIP Conference Proceedings, Vol. 1549, Issue 1; Conference: LRT 2013: 4. international workshop on low radioactivity techniques, Assergi (Italy), 10-12 Apr 2013; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
ALPHA PARTICLES
BACKGROUND RADIATION
COMPUTERIZED SIMULATION
CONTAMINATION
CRYSTALS
HIGH-PURITY GE DETECTORS
MODULATION
MONTE CARLO METHOD
MULTIPARTICLE SPECTROMETERS
NAI DETECTORS
NONLUMINOUS MATTER
PARTICLE IDENTIFICATION
POTASSIUM 40
PULSE SHAPERS
SHIELDING
THORIUM 232
UNDERGROUND
URANIUM 238