Set-up for the Neutrino Mass Search
Problem of Search for the Neutrino Mass in the Cosmologically Important Sub-Electronvolt Region by Means of Tritium Beta Decay Spectrum Measurement. Study of the Systematic Effects in New Proposed Experiment KATRIN with Existing Set-up “Troitsk Neutrino-M
Tech Area / Field
- PHY-ANU/Atomic and Nuclear Physics/Physics
3 Approved without Funding
Russian Academy of Sciences / Institute of Nuclear Research, Russia, Moscow
- All-Russian Scientific Research Institute of Non-Organic Materials named after A. Bochvar, Russia, Moscow
- Forschungszentrum Karlsruhe Technik und Umwelt / Institute für Kernphysik, Germany, Karlsruhe\nUniversity of Washington / Department of Physics / Center for Experimental Nuclear Physics and Astrophysics, USA, WA, Seattle
Project summaryThe investigation of the masses and mixings of neutrinos continues to be one of the most fundamental tasks in particle physics today with crucial implications for astrophysics and cosmology. Recently, important new experimental results in neutrino physics have been obtained and theoretical models for solving neutrino-related problems in astroparticle physics have been proposed. The problems, which aroused in connection with the new data, insistently demand the determination of absolute mass scale of neutrino in cosmologically important sub-electronvolt range. The most straightforward approach here will be direct kinematics methods and the most unique between them is the measurement of the shape of high-energy part of tritium beta-spectrum. Previous experiments which were fulfilled on the “Troitsk n-mass” set-up in Russia and on the “Neutrino Mainz” in Germany established an upper limit for the electron neutrino mass 2.05 eV and 2.2 eV correspondingly with confidence limit 95%. Penetration into sub-electronvolt region requires rising of sensitivity to mass of neutrino more then by an order, what means the suppression of experimental parameters errors more then by two orders of magnitude.
The international project KATRIN, aiming to reach sensitivity on the level mn < 0.35 eV, is at present in the stage of development. The set-up in main features will appear the huge enlargement of the “Troitsk n-mass” set-up. The jump of sensitivity by the order of magnitude poses a number of complicated technological problems connected with vitally important for the project processes of background generation and its suppression, control of systematic effects. These problems should be resolved before realization of the new project. In many cases it may be done using “Troitsk” set-up as the prototype. Most of the problems are connected with enlargement by almost three order of magnitude of the spectrometer volume in comparison with Troitsk set-up in coincidence with vacuum improvement by one-two order of magnitude. The source of molecular tritium must be radically upgraded. The intensity will rise by at least two orders of magnitude that will require appropriate improvement of handling methods.
In accordance with a foresaid, the main goals of the proposed project of ISTC are:
1. Study of background processes on the Troitsk n-mass” set-up and development of their suppression methods.
2. Investigation of nature of anomalous structure in beta spectrum of tritium, found in previous measurements and search for the possibility of its elimination, if there will be found its apparatus origin in “Troitsk n-mass” set-up.
3. Study of plasma effects in the gaseous tritium source. Study of systematic errors for the mass of neutrino connected with them.
4. Development of methods for tests of the spectrometer parameters. Development of electron gun with monochromaticity ~ 0.1 eV.
In the course of these studies it is supposed an improvement of data for the neutrino mass due to better understanding of systematics and due to possibility to increase useful measurement time as a result of installation of a new powerful refrigerator, which does not requires huge liquid nitrogen supply. It is supposed also to use regularly an isotope separator on-line, which was developed in the course of previous project ISTC # 1076. Detritisation of the set-up after completion of the experiment is one of important parts of the project. It is supposed to test some methods of solidification of the tritium contaminated vacuum oil and silicagel into materials which allow long time safe storage.