Next generation of solar neutrino experiments
All experiments designed to measure the solar neutrino flux have yielded observed interaction rates well below standard models of the sun and of electroweak interactions. That applies to charged current nuclear at all energies, in the radiochemical experiments with {sup 36}Cl and {sup 76}Ga and neutrino electron scattering for energies above about 7 MeV. The next experiment (beyond SNO) will involve one of several proposals for energy-resolved real time observations of neutrino electron scattering at lower energies. BOREXINO is a technically conservative spherical, unsegmented 200 ton liquid scintillator viewed by about 2000 photomultipliers to observe primarily {sup 7}Be neutrinos at a rate of hundreds per month. Energy resolution of about 10% and position resolution of about 10 cm is expected for recoil electrons. There is no topological information to determine recoil direction or to distinguish single electrons from gamma rays. External background will be shielded primarily by water or, possibly, an organic liquid. About half of the scintillator volume acts as an active shield. The main challenge is the purity of the scintillator itself. Technical development of this and other aspects is proceeding. A prototype test facility is under construction in the in the Gran Sasso Laboratory and is expected to start operation within a few months. At the other extreme are proposals to use liquid or cold gaseous helium as the detector. In that case, extreme purification of the sensitive region can probably be achieved by distillation at very low temperature. On the other hand, the technical problems seem daunting. To our knowledge there is, at present no plan to install a device of this kind anywhere. A very interesting proposal is to use a TPC with 10m drift length in helium at a pressure of 10 bar and temperature of 77{degrees}K.
- OSTI ID:
- 386934
- Report Number(s):
- CONF-931044-; ISSN 0003-0503; TRN: 96:026870
- Journal Information:
- Bulletin of the American Physical Society, Vol. 38, Issue 9; Conference: Fall meeting of the Division of Nuclear Physics of the American Physical Society, Pacific Grove, CA (United States), 20-23 Oct 1993; Other Information: PBD: Oct 1993
- Country of Publication:
- United States
- Language:
- English
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