Limits on Sensitivity of Large Silicon Bolometers for Solar Neutrino Detection

Abstract

Estimates are given for ultimate limits on background in proposed direct-counting measurements of neutrino scattering from large silicon crystals. Methods of background reduction are discussed. In the best case, the limiting backgrounds due to activities from cosmic-ray spallation of silicon would be less than the expected true event rate for reactor neutrino measurements of coherent neutral-current scattering from silicon nuclei. Considerable reduction of the estimated high-energy backgrounds would be required for a good signal-to-noise ratio in solar neutrino detection.

Detection of Cosmic Dark Matter

“…On the other hand, spallation products such as 68 Ge (131) or tritium (132), produced during the time the detector elements are exposed to the cosmic radiation at the surface of the Earth, may be quite disturbing because the decay energy is in the range of interest. Tritium is particularly annoying because of its low f3 energy and long lifetime, and it may have to be displaced with ordinary hydrogen (132). The main source of background will presumably be the surroundings (refrigerator, dewar, shield).…”

Neutrino-Nucleus Reactions

“…There is in fact one particular type of neutrino-nucleus reaction for which the cross section can be determined mode-independently; for the coherent scattering ν + A(gnd) → ν + A(gnd), the cross section is determined by the number of nucleons in A. The coherent process plays an important role in dark matter search [26] as well as in certain types of solar neutrino experiments [27,28,29], but we will not discuss the coherent scattering here. For a review of this topic, see [1].…”

Low-Radioactivity Background Techniques

“…Measured cosmogenic production rates (saturation activity) These calculations ar e fOf the most part based on the model of Silberberg & Tsao (67) for spallation reac tions. The lack of real measurements an d calculations(68)(69)(70) in our field may be compensated by combining information fr om the terrestrial an d space estimation approach. Table1summarizes measured production rates in natural and isotopically enriched Ge.…”