## Open Access Dissertations

January 2015

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

#### Department

Physics & Astronomy

Ephraim Fischbach

Andrew Hirsch

Mark Haugan

Fuqiang Wang

#### Abstract

The aim of this work is to make an accurate determination of the half-life of $^{32}$Si as well as to investigate reported variations in nuclear decay rates. Primarily, we focus on a previous experiment at Brookhaven National Lab (BNL) \cite{BNL}, which measured the ratio of interwoven $^{32}$Si and $^{36}$Cl decays over a 4 yr period and reported unexplained annual periodicities. Utilizing the very same sources and shuffling apparatus, we have observed the decay of $^{32}$Si and $^{36}$Cl for more than 6,000 hours each, over the last $\sim 2$ yr, while recording $\sim 5\times 10^6$ individual environmental readings. The half-life of $^{32}$Si, which has been quoted between 101(18) yr and 330(40) yr, is redetermined by this data to be $159.4\textrm{ yr} \pm 1.9\textrm{ yr (statistical)} \pm 3.7\textrm{ yr (systematic) with } \chi^2_{DOF} = 1.01$. We have also observed a periodic signal in the $^{32}$Si/$^{36}$Cl ratio decay data, similar to that in the original experiment at BNL, which we analyze at length. Finally, a related topic concerning self-induced decay and its relationship to systematic dead-time corrections is presented.

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