T. Nagafuchi

New upper bound on the electron anti-neutrino mass☆

A new upper bound ofmv < 13 eV at 95% CL has been obtained on the electron anti-neutrino mass. Thus results is based on a more than tenfold improvement in data relative to our previous measurements of the β-spectrum in 3H decay, and its in conflict with the finite mass of 17 <mv< 40 eV reported by an ITEP group

An Upper Limit for the Mass of the Electron Anti-neutrino From the Ins Experiment

Abstract The β-spectrum in 3 H decay has measured at INS with an energy resolution of 10–16 eV. The overall response function of the spectrometer system was reliably obtained with a reference 109 Cd source having the same chemical structure as the 3 H source. An upper limit of 32 eV has been obtained for the mass of the electron anti-neutrino with statistical and systematic errors.

Precise measurement of Ag KLL Auger-spectrum

Abstract The Ag KLL Auger spectrum has been measured with an energy resolution of 8 eV. The energies and the intensities of all nine lines are precisely determined with 1–2 orders of magnitude better accuracies than those in the previous experiment. The data obtained are found to be in good agreement with the theoretical calculations.

Study of energy loss of 18 keV β-rays in a Langmuir-Blodgett thin film

Abstract The energy loss of 18 keV β-rays in a very thin Langmuir-Blodgett film of a chemical compound, arachidic acid, has been studied.

Neutrino Mass and End-Point Energy of ^3H β-Decay

The end-point energy of 3 H β-decay is re-examined and found as E 0 =18582.5±4.1 eV by a new measurement of the electron energy spectrum at INS. Also, an upper limit of the electron anti-neutrino mass is obtained as m ν <29 eV by combining with the result of a previous experiment.

Precise measurement of Ag KLM and KLN Auger spectra

Abstract Ag KLM and KLN Auger spectra have been measured with a momentum resolution of 0.02%. With this resolution, most of the lines in these transitions are well separated and the complex spectral structure is revealed. Energies and intensities of these lines are precisely determined and compared with the results of the theoretical calculations.

Neutrino mass studied by measuring tritium beta-decay with an iron-free beta-ray spectrometer

Abstract The second measurement of the neutrino mass at INS has been carried out. Combining the new data with the result of the first measurement, a preliminary upper limit of 25 eV at the 95% confidence level has been obtained for the neutrino mass from only statistical consideration.

Preparation of Low-Energy Reference Electron Source with 169Yb

Large sized and uniformly deposited 169Yb sources were prepared with the following properties: the intensity variation and the deposited thickness were <±8% and ~0.4 µg/cm2, 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.

Electron Energy Loss Spectrum in Adsorbed Residual Gas on Cooled Arachidic Acid Langmuir-Blodgett Film and Its Adsorbed Gas Amount

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.

A thin, uniform, and nonvolatile tritium source for the measurement of electron antineutrino mass by means of the Langmuir—Blodgett technique

Abstract Langmuir—Blodgett (L/B) films of tritiated fatty acid were prepared to measure the electron antineutrino mass. The measurement requires that a source should be highly radioactive, homogeneous, very thin, uniform, and nonvolatile in vacuo . With regard to the volatility, the L/B film of fatty acid is, in general, not very stable in vacuo , and desorption of the source molecules results in the main background rates of the measurement and reduces the sensitivity of the mass determination. In the present work, we examined the stability of the L/B film in vacuo , and tried to improve the stability of the film by (i) perfect formation and deposition of metal soap molecules that are more resistant against evaporation than the original fatty acid molecules, and (ii) cooling of the 3 H source with liquid nitrogen in order to reduce the evaporation. Finally, a uniform and highly radioactive 3 H source, which is nonvolatile even at a pressure of 10 −4 Pa, was obtained using the Langmuir—Blodgett film of cadmium [ 3 H]icosanoate (sp act 200,000 Ci/mole).