Observation of fluctuation in beta-decay of 198Au placed in a small apparatus for neutrino detection

If self-shielding of weak interaction can be made imperfect under a specific situation, the influence may appear on neutrino interaction with other substances as well as beta decay of radioisotopes. A simple and compact apparatus has been developed for detection of neutrinos on the basis of a new hypothesis. The apparatus consists of two electrodes, raw silk and purified water. The apparatus utilizing the raw silk generated an appreciably high output voltage when it was irradiated with intense flux of reactor neutrinos nearby reactor core. The results suggest that a new aspect of weak interaction between the neutrinos and the purified water may exist under the environment in the apparatus: The raw silk is one of candidates of materials which induce a non-standard V-A interaction. To observe the influence on beta decay of radioisotopes placed in the apparatus environments, we selected the beta decay of 198Au. The radioisotope of 198Au was produced by Au foils via 197Au(nth, γ)198Au reaction. The gamma-ray spectra from the samples placed in the apparatus were measured with a high-purity Ge detector for a few days by repetitive data taking with short time-intervals. The fluctuation of decay rates for each sample was evaluated by the Fast Fourier Transformation (FFT) for the full energy peak counts in the spectrum. The decay rates of198Au in the apparatus tended to show a periodical fluctuation different from that of control samples. (author)