V. V. Sinev

Large-Volume Detector at the Baksan Neutrino Observatory for Studies of Natural Neutrino Fluxes for Purposes of Geo- and Astrophysics

At the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences, Moscow) deployed in the Caucasus mountains, it is proposed to create, at a depth corresponding to 4760 mwe, a large-volume neutrino detector on the basis of a liquid scintillator with a target mass of 10 kt. The detector in question is intended for recording natural fluxes of neutrinos whose energy may be as low as 100MeV. Neutrino fluxes from various sources are considered in the present study, and the expected effect in the proposed detector is estimated. The detector hat is being developed at the Baksan Neutrino Observatorywill become part of the world network of neutrino detectors for studying natural neutrino fluxes.

Experimental Spectrum of Reactor Antineutrinos and Spectra of Main Fissile Isotopes

Within the period between the years 1988 and 1990, the spectrum of positrons from the inverse-beta-decay reaction on a proton was measured at the Rovno atomic power plant in the course of experiments conducted there. The measured spectrum has the vastest statistics in relation to other neutrino experiments at nuclear reactors and the lowest threshold for positron detection. An experimental reactor-antineutrino spectrum was obtained on the basis of this positron spectrum and was recommended as a reference spectrum. The spectra of individual fissile isotopes were singled out from the measured antineutrino spectrum. These spectra can be used to analyze neutrino experiments performed at nuclear reactors for various compositions of the fuel in the reactor core.

Geo-Neutrinos and the Earth’s Internal Heat Flux

Predictions of geo-neutrino fluxes and the Earth’s internal heat flux made by the Hydride Earth model are discussed. The prediction of geo-neutrino fluxes can be consistent with experimental measured fluxes. The predicted value of the Earth’s internal heat flux is significantly larger than the value experimentally obtained under the assumption that the main mode of heat transport is thermal conductivity. We consider another mode of heat transport in the Earth’s crust: heat transport by hot gases created in the Earth’s crust at great depth. We discuss also experimental data supporting this idea, particularly the temperature profiles obtained in the Kola superdeep borehole.

Determination of the 14 C Concentration in a Liquid Scintillator for a Neutrino Detector

A setup has been developed for studying ultralow 14C concentrations in liquid scintillator samples for a large neutrino detector. The setup is located at the low-background underground laboratory of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) at a depth of 4900 m of water equivalent. The 14C concentrations in a liquid scintillator based on linear alkyl benzene, the background counting rates, and the spectra of particle energies deposited in the technological scintillator sample have been measured. The ratio 14C/12C = (1.41 ± 0.12) × 10–16 has been obtained. A model of the γ-ray background has been developed, with which it is possible to extract the energy spectrum of 14C and reduce the systematic uncertainty of measurements.

On the Negatively Charged Layer of the Earth’s Electric Field

Based on the hydridic Earth model, we propose a hydridic model of the Earth’s electric field. The model predicts that the negative electrode of the Earth’s capacitor is located under the Earth’s crust and the Earth’s fluids carry a positive charge. We have observed an excess of positive charge in the Earth’s crust down to kilometer depths. The model explains the unitary variation of the fair-weather atmospheric electric field strength, the change in atmospheric electric field strength and the precipitation of high-energy electrons during earthquakes.

Atmospheric Neutrinos as a Tool for Exploring the Earth’s Inner Parts

Investigation of the Earth’s inner parts requires developing new methods. It is well known that atmospheric neutrinos traverse the Earth, undergoing virtually no interaction. The change in the neutrino flux is due exclusively to neutrino oscillations, which are enhanced by the effect of Earth’s matter. At the present time, there are two projects outside Russia (PINGU and ORCA) that are aimed at detecting atmospheric neutrinos that traversed the Earth, which are supposed to be used for purposes of Earth’s tomography. The creation of a large neutrino detector on the basis of a liquid scintillator is planned at the BaksanNeutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) in the North Caucasus. After testing this detector, there will arise the possibility of employing it as part of the worldwide network of neutrino detectors for studying the Earth’s inner parts.

Measurement of the 14 C Content in Liquid Scintillators by Means of a Small-Volume Detector in the Low-Background Chamber of the Baksan Neutrino Observatory

A setup for measuring natural-radioactivity backgrounds and ultralow concentrations of the isotope 14C in samples of a liquid organic scintillator was created at the low-background laboratory of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) at a depth of 4900 mwe. The concentration of the radiocarbon 14C in a sample of a scintillator based on domestically produced linear alkylbenzene was measured, and it was found that 14C/12C (3.3 ± 0.5) × 10−17.

How Geoneutrinos can help in understanding of the Earth heat flux

The Hydride Earth model predictions of geoneutrino flux and intrinsic Earth heat flux are discussed. The geoneutrino flux predicted by the model can be adjusted to the experimental one. The predicted intrinsic Earth heat flux is significantly larger than model dependent experimental value obtained under assumption that the main heat transfer mechanism is a thermal conductivity. We introduce an additional mechanism of heat transfer in the Earths crust, namely the energy transfer by hot gases produced in the Earth crust at great depths. The experimental data supporting this idea, in particular the temperature profiles measured in the Kola super deep borehole, are discussed.

Measuring the 14C content in liquid scintillators

We are going to perform a series of measurements where the 14C/12 C ratio will be measured from several liquid scintillator samples with a dedicated setup. The setup is designed with the aim of measuring ratios smaller than 10-18. Measurements take place in two underground laboratories: in the Baksan Neutrino Observatory, Russia and in the Pyhasalmi mine, Finland. In Baksan the measurements started in 2015 and in Pyhasalmi they start in the beginning of 2015. In order to fully understand the operation of the setup and its background contributions a development of simulation packages has also been started. Low-energy neutrino detection with a liquid scintillator requires that the intrinsic 14C content in the liquid is extremely low. In the Borexino CTF detector at Gran Sasso, Italy the 14C/12C ratio of 2 × 10-18 has been achieved being the lowest 14C concentration ever measured. In principle, the older the oil or gas source that the liquid scintillator is derived of and the deeper it situates, the smaller the 14C/12C ratio is supposed to be. This, however, is not generally the case, and the ratio is probably determined by the U and Th content of the local environment.

Measuring of fissile isotope partial antineutrino spectra in direct experiment at nuclear reactor

The direct measuring method is considered to get nuclear reactor antineutrino spectrum. We suppose to isolate partial spectra of the fissile isotopes by using the method of antineutrino spectrum extraction from the inverse beta-decay reaction positron spectrum applied at Rovno experiment. This admits to increase the accuracy of partial antineutrino spectra forming the total nuclear reactor spectrum. It is important for the analysis of the reactor core fuel composition and could be applied for non-proliferation purposes.