The open archive for STFC research publications

Full Record Details

Persistent URL http://purl.org/net/epubs/work/29675
Record Status Checked
Record Id 29675
Title The Use of Photomultipliers in SNO
Abstract The comparison of the predicted and measured fluxes of neutrinos from the sun has now been carried out by four independent experiments. All four have seen a deficit between the rate measured and the rate predicted from complex, iterative models of the sun. This Solar Neutrino Problem has been a source of interest for around 20 years, with possible explainations ranging from astrophysics to new particle physics. The Sudbury Neutrino Observatory (SNO) aims to resolve the problem by the direct comparison of the flux of electron neutrinos to the flux of all flavours of neutrinos, and hence check various models which suggest that the neutrinos are oscillating from electron to muon or tau flavour on their passage from the core of the sun to the earth. SNO itself is a 1 kilo-tonne heavy water Cerenkov detector, which can measure the electron neutrino flux by the break-up of deuterium via a W boson, the CC reaction; and can measure the flux of all neutrinos with the weak disintegration of the deuteron via a Z boson, the NC reaction. In order to make the comparison between the two channels, the backgrounds on each channel must be very well known. The main sources of background are the long lived isotopes of thorium and uranium, and their subsequent decay chains, and to a lesser extent (40)K. The cleanliness requirements for the detector have meant that new regimes of contamination have had to be considered, and new techniques for assay developed. In order to assay to the levels required, new counters have been developed by the author which use the fast beta-alpha coincidences at the ends of the uranium and thorium chains. The counters have a high efficiency, source/counter separation, and at present have a low enough background to assay the heavy water in SNO to the required levels. The development of these counters has gone hand-in-hand with the investigation and calibration of the ion extraction process, seeded ultra-filtration, at the low levels required.
Organisation CCLRC
Funding Information
Related Research Object(s):
Licence Information:
Language English (EN)
Type Details URI(s) Local file(s) Year
Thesis RAL Theses RAL-TH-1998-005. 1998. 1998