Searches for solar-influenced radioactive decay anomalies using spacecraft RTGs

Abstract

Experiments showing a seasonal variation of the nuclear decay rates of a number of different nuclei, and decay anomalies apparently related to solar flares and solar rotation, have suggested that the Sun may somehow be influencing nuclear decay processes. Recently, Cooper searched for such an effect in 238 Pu nuclei contained in the radioisotope thermoelectric generators (RTGs) on board the Cassini spacecraft. In this paper we modify and extend Cooper's analysis to obtain constraints on anomalous decays of 238 Pu over a wider range of models, but these limits cannot be applied to other nuclei if the anomaly is composition-dependent. We also show that it may require very high sensitivity for terrestrial experiments to discriminate among some models if such a decay anomaly exists, motivating the consideration of future spacecraft experiments which would require less precision.

Spectral content of 22Na/44Ti decay data: implications for a solar influence

“…Cooper (Cooper 2009) analyzed data from the radioisotope thermoelectric generators (RTGs) onboard the Cassini spacecraft enroute to Saturn and found no evidence for a dependence of the decay rate of 238 Pu (which powers the RTGs) on the Cassini-Sun separation. Our group has recently carried out a more detailed analysis of the RTG data, and we have shown that in fact there are no conflicts between the Cassini results and the previously reported decay anomalies (Krause et al 2012). Additionally, it was noted that even if the RTG data analyzed were sufficiently good to support the claims in Ref.…”

The uncertainty of the half-life

“…The initial Pb isotopic ratios (extracted from meteorites) and age of the system are the two factors determining the present day Pb isotopic ratios. In a closed system, equation (7) represents a linear relationship in which the slope depends on the age. The age of Earth, 4.54 (5) 10 9 a, was thus obtained (see e.g.…”

“…decays that proceed through electron capture or internal conversion [3]. In recent years, controversy arose due to claims that half-lives are affected by temperature, conductivity of the hosting material, solar proximity or neutrino flux, which were subsequently refuted by others (see [7][8][9][10][11][12]).…”

Eventdisplay: An Analysis and Reconstruction Package for Ground-based Gamma-ray Astronomy

“…There are a variety of options for the gamma-ray hadron separation routine in Eventdisplay, ranging from box cuts using single-telescope or stereo parameters to energy-dependent cuts based on multivariate methods: Boosted decision trees (BDT) as implemented in the TMVA package [15] show the best performance of the used gamma-hadron separation methods. The BDT can be trained and applied in several energy and off-axis bins; see [16] for an extensive description of the BDT analysis and performance.…”