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Neutron emission caused by the spontaneous appearance of a hole state in a nucleus, which could take place as a manifestation of violation of the Pauli principle, was searched for. Neutrons from natural lead were found to be less than 1.6*10-3 neutrons/s kg which gives a lifetime of tau >1.0*1020 y (0.99 CL). It is shown that the present measurement limits spontaneous appearance of a hole state better than the measurement of nuclear gamma -transitions by many orders of magnitude.

A third measurement of the electron antineutrino mass by tritium beta decay at INS was carried out after making some improvements for enhancing the counting rate. Langmuir-Blodgett film beta -ray sources with a 5-times larger area (60*200 mm2) than those used in previous measurements were prepared, and a new position sensitive beta -detector with a 6-times larger sensitive area was developed. Using this modified equipment, about 150000 events, more than one order of magnitude higher numbers than in previous measurements, were accumulated in the last 100-eV region below the end-point energy.

The energy-loss spectra of 18 keV electrons in adsorbed residual gas on Langmuir-Blodgett film, made from arachidic acid (C20H40O2) and cooled at temperatures of -10°C, -35°C and -60°C, were measured through use of an electron source that also acted as an adsorbent. In addition, the amount of adsorbed residual gas was estimated from the energy-loss probability.

Large sized and uniformly deposited 169Yb sources were prepared with the following properties: the intensity variation and the deposited thickness were 2, respectively, for the source sizes of 35×45 mm2 and 20×100 mm2 with the deposited activity of 20-50 µCi, as an energy reference source for the neutrino mass measurement at INS. The technical details of the preparation: the processes of chemical separation and purification, and vacuum-deposition, are here reported.