Calorimetric method for determination of 51 Cr neutrino source activity
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Calorimetric Method for Determination of 51Cr Neutrino Source Activity1 E. P. Veretenkin*, V. N. Gavrin, S. N. Danshin, T. V. Ibragimova, Yu. P. Kozlova, and I. N. Mirmov Institute for Nuclear Research, Russian Academy of Sciences, pr. 60letyia Oktyabrya 7a, Moscow, 117312 Russia *email: [email protected] Received January 23, 2015
Abstract—Experimental study of nonstandard neutrino properties using highintensity artificial neutrino sources requires the activity of the sources to be determined with high accuracy. In the BEST project, a cal orimetric system for measurement of the activity of highintensity (a few MCi) neutrino sources based on 51Cr with an accuracy of 0.5–1% is created. In the paper, the main factors affecting the accuracy of determin ing the neutrino source activity are discussed. The calorimetric system design and the calibration results using a thermal simulator of the source are presented. Keywords: artificial neutrino source, neutrino source activity, heat release, thermal power, calorimetric method, calorimetric system. DOI: 10.1134/S1063778815130347
2. BASIC FACTORS DETERMINING THE ACCURACY OF THE CALORIMETRIC METHOD FOR MEASURING THE ACTIVITY OF ARTIFICIAL NEUTRINO SOURCES
1. INTRODUCTION The use of highintensity neutrino sources is con sidered currently as one of the main instruments for the investigation of nonstandard neutrino properties [1, 2]. These sources emit electron neutrinos with wellknown spectra and their intensities can be mea sured with high accuracy. For the first time, artificial neutrino sources were used for detector calibration in four gallium experi ments SAGE [3, 4] and GALLEX [5]. In the SAGE calibration experiment, the calori metric method was applied for determining the activ ity of a source with intensity of ~0.5 MCi, which cor responded to the heat release of ~90 W. The measure ment accuracy of the source activity using the calorimetric method subject to the statistical and sys tematic uncertainties was 1.2% [3]. The BEST project proposes to use a 3MCi 51Cr source with the starting thermal power of about 650 W. A newly created calori metric system uses the heating of the coolant for the measurement of the heat release with accuracy of 0.5– 1%. In this paper, we present the design of the calori metric system and the factors determining the accu racy of the measurements of source activity. 1 The article was translated by the authors.
Since the decay of 51Cr is accompanied by energy release, the source activity can be determined via calo rimetric measurements of its heat release. The accu racy of measuring the activity of artificial neutrino sources using the calorimetric method depends on many factors and primarily on the uncertainties of the energy release in the 51Cr decay. Table 1 shows these values obtained taking into account new data of 51Cr decay characteristics [6]. The average energy liber ated, which can be registered in the form of heat, is 36.750 ± 0.084 keV/decay. Compared to the previ ously used data [3], the mean value of the
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