Cosmogenic background study for a 100Mo-based bolometric demonstration experiment at China JinPing underground Laboratory

Abstract

We perform simulation study for a 10-kg 100 Mo-based bolometeric demonstration experiment for neutrinoless double-beta decay (0νββ) search at China JinPing underground Laboratory (CJPL). Cosmogenic production of radionuclides in 100 Mo-enriched lithium molybdate crystals and copper components of the detector system are studied using Geant4 toolkit based on the simulated cosmic ray data from the CRY library. Background energy spectra of the cosmogenic radionuclides including 56 Co, 82 Rb and 88 Y which are harmful for the 100 Mo-based 0νββ experiment are investigated. We then evaluate the total cosmogenic background level in the 100 Mo 0νββ search energy region of interest (ROI) for the demonstration experiment. After one year of cooling down underground, the residual background contribution is found to be 1.8×10 −6 cts/kg/keV/yr and 3.3×10 −4 cts/kg/keV/yr from crystals and copper components, respectively. Furthermore, underground cosmogenic activation of copper and lithium molybdate crystal is calculated based on the simulation spectra of neutron and proton in CJPL. The underground cosmogenic background is found to be negligible in the ROI.