Estimation of the neutrino rest mass from measurements of the tritium β-spectrum

The problems connected with performing tritium β spectrum measurements close to the boundary point with the purpose to specify data on rest mass of antineutrino are discussed. The improved experimental installation created on the base of iron-free toroidal β spectrometer with four-fold electron deviation is described. As β electron detectors the threechannel proportional chamber filled with argon with methyl alcohol addition is used. The total chamber length is 40 mm. The detector efficiency constitutes approximately 50%, the background is reduced to 0.05 c-1. The application of the three-channel detector enables to increase the data acquisition rate 2.5 times ass compared with experiments in which ordinary proportional counters are used. To increase the accuracy of energy measurement the electron source unit has been improved. In the present experiment two nonequipotential sources have been placed: main source of tritium β particle and calibration source. The processing of measurement results is considered in detail. When determining confidence level for antineu trino rest mass the method of mathematical modelling is applied. For the rest mass anti νsub(e) the lower limit has been obtained for the first time, 14<=msub(anti μ(sub(e))<=eV. For tritium β decay energy the value E0=18577+-13 eV has been found