Further studies of the OMNIS supernova neutrino observatory: optimisation of detector configuration and possible extension to solar neutrinos

The basic design principles and earlier origins of OMNIS (Observatory for M ultiflavour Neutrino Interactions from Supernovae) have been described in a previous paper [Astropart. Phys. 8 (1997) 27]. Its purpose would be to rec ord a large number of mu and tau neutrinos from a supernova burst, compleme nting other world detectors which observe mainly electron antineutrinos. Th is would enable a cosmologically significant neutrino mass to be measured o r definitely excluded by the arrival time profile. The detector is based on neutral current excitation of lead and iron target nuclei followed by rele ase of neutrons. Further studies by Fuller et al. [Phys. Rev. D59 (1999) 08 5005] have shown that a distinctive two-neutron signal will result from an MSW transition between v(mu,tau) and v(e) in the supernova, thus adding fur ther physics capability to OMNIS. In this paper we summarise the published neutron production estimates for different targets, with and without mixing , and discuss the results of simulations of a range of target/detector conf igurations, with the objective of optimising the single and double neutron signals from a given target mass. Discussions are included of the choice of neutron detection method, and the effect of neutron and gamma backgrounds. It is further proposed that OMNIS detector modules might be designed to in clude real-time solar neutrino spectroscopy using the nuclear excitation pr inciple devised by Raghavan [Phys. Rev. Lett. 78 (1997) 3618]. (C) 2001 Els evier Science B.V. All rights reserved.