Preparation and characterization of a $^{39}Ar$ sample and study of the $^{39}Ar(n_{th},\alpha)^{36}S$ reaction

The $^{39}$Ar(n$_{\rm th}$,$\alpha$)$^{36}$S reaction has been studied for the first time. A sample containing $2.85 \times 10^{14}$ $^{39}$Ar atoms, was produced at the ISOLDE facility at CERN. The number of $^{39}$Ar atoms in the layer was determined by measuring the $^{39}$Ar $\beta$-activity using a primary standardization method. Subsequently, the sample was irradiated with thermal neutrons at the High Flux Reactor of the ILL. An upper limit of 0.29~b was obtained for the $^{39}$Ar(n$_{\rm th}$,$\alpha$)$^{36}$S reaction cross-section.