Speaker
Description
Abstract
Understanding and mitigation of background plays a crucial role in rare decay studies [1] and measurements of low cross sections relevant to nuclear astrophysics processes [2]. While anti-Compton shield (ACS) helps in enhancing the photopeak efficiency, muon induced interactions in the ACS can introduce additional background. With this motivation, measurements are carried out using low background counting setup CRADLE at TIFR (Mumbai) [3], comprising a 35$\%$ carbon fiber body HPGe detector surrounded by a 2.5 cm thick annular BGO shield and low activity lead shield (~ 10 cm). Two plastic scintillators (50 cm $\times$ 50 cm $\times$ 1 cm) are positioned on the top of the HPGe setup for detection of muons. Data was recorded using a CAEN N6724 digitizer (14-bit, 100 MS/s) with the BGO for 30 days and without the BGO for 15 days. Analysis is carried out for both these configurations, with and without plastic coincidence, in ROOT with appropriate time normalisation and chance corrections.
$\hspace{1cm}$ In singles spectra, several additional gamma rays are observed and intensity of a few other background lines like 1460 keV is enhanced. However, in the muon gated spectra, no additional n-induced gamma ray are observed at the measured level of the sensitivity. For $^{96}$Zr beta decay, that is $^{96}$Zr ${\rightarrow}$ $^{96}$Nb $\rightarrow$ $^{96}$Mo$^*$, the regions of interest (ROI) are near the expected photopeaks of 569, 778 and 1091 keV [4]. Hence, 569 keV arising from $^{207}$Pb(n,n$^\prime\gamma)$ can be a source of background. Measurements with CsI annular shield are also in progress. A comparison of background improvements with CsI and BGO annular shields will be presented together with Geant4 simulations.
References
[1] Dolinski et al., Annual Review of Nuclear and Particle Science, 69, 219, (2019)
[2] Denise Piatti, EPJ Web Conf. 297, 01009 (2024)
[3] G. Gupta et al., Proceedings of the DAE Symp. on Nucl. Phys. 63, 232, (2018)}
[4] S. Thakur, et al., Il Nuovo Cimento C 45, 24 (2022)
