On the interpretation of annual oscillations in 32Si and 36Cl decay rate measurements

Abstract

The 32Si decay rate measurement data of Alburger et al. obtained in 1982–1986 at Brookhaven National Laboratory have been presented repeatedly as evidence for solar neutrino-induced beta decay. The count rates show an annual sinusoidal oscillation of about 0.1% amplitude and maximum at February–March. Several authors have claimed that the annual oscillations could not be explained by environmental influences on the set-up, and they questioned the invariability of the decay constant. They hypothesised a correlation with changes in the solar neutrino flux due to annual variations in the Earth-Sun distance, in spite of an obvious mismatch in amplitude and phase. In this work, environmental conditions at the time of the experiment are presented. The 32Si decay rate measurements appear to be inversely correlated with the dew point in a nearby weather station. Susceptibility of the detection set-up to local temperature and humidity conditions is a likely cause of the observed instabilities in the measured decay rates. Similar conclusions apply to 36Cl decay rates measured at Ohio State University in 2005–2012.

Role of ambient humidity underestimated in research on correlation between radioactive decay rates and space weather

“…They reported positive or negative correlations with geomagnetic activity (GMA) and cosmic-ray activity (CRA). This assertion is at variance with the most accurate measurements of radioactivity, which support the validity of the exponential-decay law 4 – 14 . If a causal relationship between ‘space weather’ and radioactive decay rates were true, it would invalidate the notion of invariable decay constants and have unforeseeable practical and theoretical implications.…”

Ambient humidity, the overlooked influencer of radioactivity measurements

“…The data show no correlation with humidity. Undisclosed results of ongoing 32 Si decay rate measurements promise exceptional stability, in contrast with the seasonal variations observed in the BNL/Purdue data [67,68], which were found to be correlated with ambient humidity [17,18].…”

“…Some authors are adamant in their claims that observed violations of the exponentialdecay law cannot be attributed to environmental conditions in the laboratory [5,6]. However, using historical weather data available on meteorological websites, a link with terrestrial weather could be established for several infamous experiments [1,2,4,[7][8][9][10][11][12][13][14][15][16][17][18][19].…”

Empirical decomposition and error propagation of medium-term instabilities in half-life determinations

“…Typical examples are daily or annual oscillations due to environmental influences, jumps in detection efficiency due to occasional source repositioning, step functions due to instrument scaling switches and recalibrations, and non-random variations in background and impurity activity. Observations of such anomalies have been the root cause of speculations on the variability of decay constants, in spite of convincing evidence of the validity of the exponential-decay law in stable measurement set-ups [26][27][28][29][30][31][32][33][34][35][36][37][38][39].…”