Air humidity and annual oscillations in Sr-90/Y-90 and Co-60 decay rate measurements

Parkhomov published decay rate measurements of Sr-90/Y-90 and Co-60 beta decay sources with Geiger-Muller counters which showed annual cyclic deviations with less than 0.2% amplitude from a purely exponential slope. He investigated instrument instability induced by environmental parameters, yet did not find a clear coincidence with local temperature, atmospheric pressure, and relative humidity. Parkhomov hypothesised that gravitationally-focussed 'slow' cosmic neutrinos influenced beta decay. In the current work, environmental conditions in the Moscow area at the time of the experiment are presented. There appears to be a resemblance of the shape of the annual Sr-90/Y-90 decay rate anomalies with the inverse of the absolute air humidity, albeit with an apparent time shift of 0.05-0.15 year. Humidity may have influenced the range of beta particles in air, as well as geometric and electronic properties of the detection set-up, however causality could not be unambiguously demonstrated. The instabilities in the Co-60 data were more difficult to correlate with environmental data, except for some similarities with temperature and external dew point.