Development of a low-background neutron detector array

A low-background neutron detector array was developed to measure the cross section of the C-13(alpha,n)O-16 reaction, which is the neutron source for the s-process in AGB stars, in the Gamow window (E-c.m. = 190 +/- 40 keV) at the China Jinping Underground Laboratory (CJPL). The detector array consists of 24 He-3 proportional counters embedded in a polyethylene cube. Owing to the deep underground location and a borated polyethylene shield around the detector array, a low background of 4.5(2)/h was achieved. The V-51(p, n)Cr-51 reaction was used to determine the neutron detection efficiency of the array for neutrons with energies E-n < 1 MeV. Geant4 simulations are shown to effectively reproduce the experimental results. They were used to extrapolate the detection efficiency to higher energies for neutrons emitted in the C-13(alpha,n)O-16 reaction. The theoretical angular distributions of the C-13(alpha,n)O-16 reaction were shown to be important in the estimation of the uncertainties of the detection efficiency.

Automated summary

A low-background neutron detector array was developed to measure the cross section of the C-13(alpha,n)O-16 reaction, which is the neutron source for the s-process in AGB stars, in the Gamow window at the China Jinping Underground Laboratory. The detector array achieved a low background of 4.5(2)/h due to its deep underground location and borated polyethylene shield. The neutron detection efficiency of the array was determined using the V-51(p, n)Cr-51 reaction.