Study of (alpha,n) reactions from the Calibration Sources of the MAJORANA DEMONSTRATOR Experiment

Neutrinoless double beta $(0 \nu \beta \beta)$ decay is a hypothesized lepton-number-violating nuclear transition. If observed, $0 \nu \beta \beta $ decay would unambiguously demonstrate the violation of an empirical symmetry of the Standard Model and establish the Majorana nature of neutrinos. The MAJORANA DEMONSTRATOR experiment, currently operating at the 4850$^{\prime}$ level of the Sanford Underground Research Facility in Lead SD, is searching for such decay in $^{76}$Ge with high purity Germanium (HPGe) detectors. MAJORANA has achieved an excellent energy resolution of 2.5 keV FWHM and a low background rate. The DEMONSTRATOR regularly deploys a $^{228}$Th line source to perform energy calibration based on the detection of the gamma ray photopeaks. The calibration source inevitably produces several alpha particles with energies of several MeV within the $^{228}$Th chain before it ends with the stable $^{208}$Pb. When traversing through surrounding materials, these alpha particles can potentially produce neutrons and coincident gammas from $(\alpha, n)$ reactions and nuclear de-excitations that follow. In this talk, we will discuss our efforts studying such neutrons originating from the calibration sources via their coincident gamma signatures.