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Lithium Detector of Solar Neutrinos

#1347


Development of Lithium Detector of Solar Neutrinos on a Basis of Prototype with 300 kgs of Lithium

Tech Area / Field

  • PHY-PFA/Particles, Fields and Accelerator Physics/Physics
  • INS-DET/Detection Devices/Instrumentation

Status
3 Approved without Funding

Registration date
17.09.1998

Leading Institute
Russian Academy of Sciences / Institute of Nuclear Research, Russia, Moscow

Supporting institutes

  • NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad\nFEI (IPPE), Russia, Kaluga reg., Obninsk

Collaborators

  • Institute for Advanced Study, USA, NJ, Princeton

Project summary

The aim of the project is to develop a lithium detector of solar neutrinos on 10 tons of lithium using a prototype on 300 kgs of metallic lithium. The main task of the work is to optimize all technological procedures in geometry similar to geometry of a full-scale installation to the level adequate to perform a solar neutrino experiment.

The final result of the work will be the developed technology of 7Be recovery from metallic lithium with the coefficient of extraction no less than 90% and good reproducibility of the results on the prototype of lithium detector of solar neutrinos. The tests will be done of all systems of the installation, a safe handling of melted lithium will be developed. To prove the efficiency of this technology for solar neutrino experiment the yield of 7Be by cosmic rays at sea level and by fast neutrons of Pu-Be neutron source will be measured. By the results obtained a technical project of a lithium detector of solar neutrinos on 10 tons of lithium will be prepared. The technology of fabrication of an artificial neutrino source on a basis of 65Zn of total activity of about 30,000 Ci will be developed for the calibration of lithium detector by the neutrino source to prove the reliability of lithium experiment. This work will enable to determine the dimensions and design of the central channel to accomodate a neutrino source for final installation on 10 tons of lithium. By completion of this project it will be possible to start construction of full-scale lithium detector for the solar neutrino research.

The performance of this project will enable group of scientists and experts engaged till now in sphere of development of nuclear weapon and other kinds of military engineering, to be swiched to development of the neutrino detector for realization of basic research in the field of elementary particles and neutrino astrophysics.

The urgency of a task is determined by the observed deficit of solar neutrinos in comparison with the theoretical predictions. It means that either we miss something important in the course of thermonuclear reactions in the Sun, what may be very interesting from a practical point of view, or neutrino has new properties, this will signify the discovery of New Physics beyond the standard model of minimal electroweak theory describing all the experimental data available by now (see, for example, A.V.Kopylov "The problem of solar neutrinos: from past to future" in Russian Journal Priroda (Nature) N5(1998), N6(1998)). The last possibility has become more obvious as a result of a recent discovery of atmospheric neutrino oscillations by the Japanese experiment SuperKamiokande.

The main advantage of lithium detector is that it is the only proposed solar neutrino detector which has high sensitivity to pep-neutrinos; the flux of these neutrinos is directly connected with the luminosity of the Sun and the energy of these neutrinos is exactly in the range most interesting for identifying new properties of neutrinos. The results from lithium detector will be invaluable for identifying parameters of neutrino oscillations (i.e. mixing angles and masses of neutrinos). Moreover, unlike for other detectors, the neutrino capture cross-sections in Li are guaranteed by well established isospin connections between mirror nuclei. If the measured effect from solar neutrinos in lithium detector is less than 19 SNU, what should be observed if the flux of intermediate energy neutrinos is substantially lower than standard solar model predicts, then this result could be interpreted only in framework of New Physics as a strong attenuation of the flux of pep-neutrinos due to neutrino flavor conversion in the matter of the Sun (MSW-effect with small mixing angles). Low flux of other neutrinos from this energy range is of less significance as it doesn’t exclude interpretation within framework of standard model. Due to large Sun-Earth distance lithium experiment on solar neutrinos will enable to investigate a mass range of lighter pair of neutrinos inaccessible for the experiments done with the artificially generated neutrinos.

The results obtained may find the application for the development of safety of nuclear reactors with lithium coolant, in ecology, for the facilities and in industry utilizing high purity lithium. These results can be used also to produce isotopes for medicine (tomography, cancer treatment) by means of extraction from the irradiated metallic targets.

As a working material (target) of the detector a metallic lithium is used in this project. The principle of lithium detector is the same as used in other radiochemical detectors (chlorine, gallium). A few tens atoms of 7Be produced by solar neutrinos in 10 tons of lithium during the exposure are extracted by a certain technology tested on small masses of metallic lithium. The number of atoms produced and extracted is determined by counting the pulses from a decay of 7Be (half-life 53 days) by means of a cryogenic microcalorimeter. The possibility of using this technique was demonstrated in joint work with the laboratory of professor S.Vitale at Genoa, Italy and the results obtained were published in Phys. Lett. B398 (1997) 187 and in NIM A401 (1997) 311. The number of atoms of 7Be determines the flux of solar neutrinos with the energy higher than a threshold, 0.86 MeV for lithium detector.

Participation of foreign scientists in this project may be useful primarily for the development of low background cryogenic detector for counting of 7Be in lithium experiment on solar neutrinos. The project is also interested in good analytical base to monitor the concentration of beryllium in lithium contained solutions and of impurities in samples of beryllium extracted from lithium.


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