Forty Years to the Artemovsk Scintillation Detector for Neutrinos
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EMENTARY PARTICLES AND FIELDS Experiment
Forty Years to the Artemovsk Scintillation Detector for Neutrinos A. G. Antonenko, V. P. Borshchevsky, R. I. Enikeev, O. V. Ochkas, O. G. Ryazhskaya*, L. V. Chernyshov, A. P. Yarosh, and N. A. Iarosh Institute for Nuclear Research, Russian Academy of Sciences, pr. Shestidesyatiletiya Oktyabrya 7a, Moscow, 117312 Russia Received June 14, 2017
Abstract—The current status of the ASD (Artemovsk scintillation detector) experiment aimed at search for a neutrino flux from gravitational collapses of stellar cores is presented. Experimental data obtained for 40 years of operation of the detector situated in a salt mine at a depth of 570 mwe are processed. The results obtained by calculating the expected signal in the detector on the basis of two models of supernova explosion are described. No candidates for neutrino bursts from gravitational star collapses have been revealed: the limit on the frequency of gravitational collapses was found to be less than one event per 17.15 yr at a 90% confidence level (fcol < 0.058 yr−1 ). DOI: 10.1134/S1063778818010040
INTRODUCTION
1. DESCRIPTION OF THE ASD EXPERIMENT
Nine detectors that are able to detect neutrino bursts from gravitational collapses on the basis of neutrino interaction with protons and carbon, oxygen, iron, chlorine, and lead nuclei are operating at the present time worldwide. These are LVD, SK, KamLAND, ASD (Artemovsk scintillation detector), HALO, IceCube, DayaBay, Borexino, and BUST (Baksan scintillation telescope).
The Artemovsk Scintillation Detector (ASD) is located in a salt mine at a depth of 570 mwe (see Fig. 1). The ASD experiment is aimed primarily at search for neutrino radiation from stars collapsing in the Milky Way Galaxy. The target used in these searches for neutrino radiation from star collapses contains 105 t of a scintillator and 1000 t of salt (NaCl) surrounding the detector.
A simultaneous operation of these detectors in the on-line mode makes it possible to fix collapses of stellar cores with a high reliability and to specify the time and, possibly, the direction for astronomical observations. Information about the properties of detected neutrinos is necessary for obtaining deeper insight into processes proceeding in a star at the ultimate stage of its evolution.
The natural-radioactivity background in salt is approximately 300 times lower than in ordinary rock. The deployment depth of this detector also makes it possible to accumulate data on neutron interactions within relatively short periods and is sufficiently large for extrapolating data to other depths [2]. The detection efficiency for neutrons moderated to thermal energies is about 80% for ASD, provided that neutron sources are uniformly distributed over the scintillator volume. The detectors has the shape of a cylinder 556 ± 3 cm in diameter and 547 cm in height; it contains 105 t of a liquid scintillator based on white spirit (Cn H2n , where n ≈ 10). The height of the scintillator column is 540 cm, and the scintillator density is 0.78 g/cm3 . The si
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