We propose a new experiment to search for a sterile neutrino in a few keV mass range at the Troitsk nu-mass facility. The expected signature corresponds to a kink in the electron energy spectrum in tritium beta-decay. The new goal compared to our pre
vious experiment will be precision spectrum measurements well below end point. The experimental installation consists of a windowless gaseous tritium source and a high resolution electromagnetic spectrometer. We estimate that the current bounds on the sterile neutrino mixing parameter can be improved by an order of magnitude in the mass range under 5 keV without major upgrade of the existing equipment. Upgrades of calibration, data acquisition and high voltage systems will allow to improve the bounds by another order of magnitude.
An electron antineutrino mass has been measured in tritium beta-decay in the Troitsk nu-mass experiment. The setup consists of a windowless gaseous tritium source and an electrostatic electron spectrometer. The whole data set acquired from 1994 to 20
04 was reanalysed. A thorough selection of data with the reliable experimental conditions has been performed. We checked every known systematic effect and got the following experimental estimate for neutrino mass squared m_{nu}^{2}=-0.67+/- 2.53 {eV}^{2}. This gives an experimental upper sensitivity limit of m_{nu}<2.2 eV and upper limit estimates m_{nu}<2.12 eV, 95% C.L. for Bayesian statistics and m_{nu}<2.05 eV, 95% C.L. for the Feldman and Cousins approach.
