Search

Cadmium-116 is one of the favorable candidates for neutrinoless double-beta decay ( 0 ν β β ) searches from both theoretical and experimental points of view, in particular thanks to the high energy of the decay (2813.49 keV), the possibility of the industrial enrichment in 116 Cd and its use in the well-established production of cadmium tungstate crystal scintillators. In this work, we present low-temperature tests of two 0.6 kg 116 CdWO 4 crystals enriched in 116 Cd to 82 % as scintillating bolometers. These detectors were operated underground, with one at the Laboratoire Souterrain de Modane (LSM) in France and the second at the Laboratorio Subterraneo de Canfranc (LSC) in Spain. The two crystals are coupled to bolometric Ge light detectors in order to register the scintillation light. The double readout of heat and scintillation enables reduction in the background in the region of interest by discriminating between different populations of particles. The main goal of these tests is the study of the crystals' radiopurity and the detectors' performance. The achieved results are extremely promising, in particular, the detectors demonstrate a high energy resolution (11–16 keV FWHM at 2615 keV) and a high-efficiency discrimination of the alpha background ( ∼ 20 σ ). These results, achieved for the first time with large mass enriched 116 CdWO 4 crystals, demonstrate prospects of the bolometric technology for high-sensitivity searches of 116 Cd 0 ν β β decay. [ABSTRACT FROM AUTHOR]

An increase in ambient dose equivalent rate during precipitation events is a well known phenomenon that is easily identified by dose rate monitoring networks. Despite the invaluable information these monitors usually provide, they cannot identify the radioisotopes involved in these radiological alterations nor quantify their activity concentrations. Commercial systems based on passive gamma spectrometry using scintillation detectors allow to identify the radionuclides that increase during rainfall events but they cannot infer if they are deposited on ground or linked to the airborne particles. In 2016 an air monitoring station based on sample retention and scintillator gamma spectrometer was custom-designed and integrated into the automatic and quasi-real-time Radiological Alert Network of Extremadura (RARE) in south western Spain. In this work, it is presented how the capabilities of our system take advantage of the distinction between the radionuclides that are deposited and the radionuclides that are presented in airborne during rainy events. However, during the operation of RARE's homemade monitoring station based on sample retention and gamma-spectrometry, some shortcomings to meet the requirements appertained to real-time radiological networks, such as efficiency, were identified. Concretely, the station was targeted at monitoring the activity of gamma-emitting radioisotopes in airborne, but the relatively poor energy resolution of the gamma scintillation detectors employed meant that exceptionally high concentrations of radon decay products (such as 214Pb) in the area made it very difficult to identify and quantify the activity levels of some anthropogenic radioisotopes such as 131I, with there being a significant number of false positives and substantial increase in those isotopes' minimum detectable activities. This paper describes the simple approach that has been implemented in order to overcome the aforementioned analytical difficulty in situations where the activity concentration of radioiodine in air could be of the order of natural radon concentration, for example, when effluent releases from nuclear facilities permitted under authorities' regulations. • A study of scavenging of 222Rn daughters during a rainfall using real-time airborne gamma spectrometry is shown. • The capabilities of the automatic airborne gamma spectrometric monitoring station based on sample retention are presented. • A simple calculation method to solve overlapping I-131/Pb-214 photopeaks is implemented. [ABSTRACT FROM AUTHOR]

The ANAIS (Annual modulation with NaI(Tl) Scintillators) experiment aims at the confirmation or refutation of the DAMA/LIBRA positive annual modulation signal in the low energy detection rate, using the same target and technique, at the Canfranc Underground Laboratory (LSC) in Spain. ANAIS-112, consisting of nine 12.5 kg NaI(Tl) modules produced by Alpha Spectra Inc. in a 3 × 3 matrix configuration, is taking data smoothly in "dark matter search" mode since August, 2017, after a commissioning phase and operation of the first detectors during the last years in various set-ups. A large effort has been carried out within ANAIS to characterize the background of sodium iodide detectors, before unblinding the data and performing the first annual modulation analysis. Here, the background models developed for all the nine ANAIS-112 detectors are presented. Measured spectra from threshold to high energy in different conditions are well described by the models based on quantified activities independently estimated following several approaches. In the region from 1 to 6 keV ee the measured, efficiency corrected background level is 3.58 ± 0.02 keV - 1 kg - 1 day - 1 ; NaI crystal bulk contamination is the dominant background source being 210 Pb 40 K 22 Na and 3 H contributions the most relevant ones. This background level, added to the achieved 1 keV ee analysis threshold (thanks to the outstanding light collection and robust filtering procedures developed), allow ANAIS-112 to be sensitive to the modulation amplitude measured by DAMA/LIBRA, and able to explore at three sigma level in 5 years the WIMP parameter region singled out by this experiment. [ABSTRACT FROM AUTHOR]