1/27/2024 0 Comments Sno plus merchandise neutrinoIt was crucial to the success of this experiment to make the components of SNO very clean and, in particular, to reduce the radio-activity within the heavy water to exceedingly low levels. Figure 2 shows what the detector “sees”: the photo-multiplier tubes that were hit following the creation of an electron by an electron neutrino. Figure 1 shows the layout of the SNO detector, which is located about 2 km underground in Inco’s Creighton nickel mine near Sudbury, Canada, so as to all but eliminate cosmic rays from reaching the detector. This sphere was surrounded by 7000 tonnes of ultra-pure water to shield against radioactivity. Neutrino interactions were detected by 9456 photomultiplier tubes surrounding the heavy water, which was contained in a 12 m diameter acrylic sphere. Scientists from Canada, the US and the UK designed SNO to attain a detection rate of about 10 solar neutrinos a day using 1000 tonnes of heavy water. Photomultiplier tubes mounted on a geodesic structure detect Cherenkov light from relativistic electrons following a neutrino interaction. This is the principle behind the SNO experiment. A comparison of the flux of electron neutrinos with that of all flavours can then reveal whether flavour transformation is the cause of the solar-neutrino deficit. In heavy water neutrinos of all types can break a deuteron into its constituent proton and neutron (the neutral-current reaction), while only electron neutrinos can change the deuteron into two protons and release an electron (the charged-current reaction). In 1985, the late Herb Chen pointed out that heavy water (D 2O) has a unique advantage when it comes to detecting the neutrinos from 8B decays in the solar-fusion process, as it enables both the number of electron neutrinos and the number of all types of neutrinos to be measured. This oscillation mechanism requires that neutrinos have non-zero mass. A possible explanation, suggested by Vladimir Gribov and Bruno Pontecorvo in 1969, was that some of the electron-neutrinos, which are produced in the Sun, “oscillated” into neutrinos that could not be detected in Davis’s detector. The Kamiokande II experiment in Japan confirmed this deficit, which became known as the solar-neutrino problem, while other detectors saw related shortfalls in the number of solar neutrinos. Surprisingly, he found only about a third of the number predicted from models of the Sun’s output. Ray Davis’s radiochemical experiment first detected solar neutrinos in 1967, a discovery for which he shared the 2002 Nobel Prize in Physics ( CERN Courier December 2002 p15). This observation explained the long-standing puzzle as to why previous experiments had seen fewer solar neutrinos than predicted and also confirmed that these elusive particles have mass. During this time the observatory saw evidence that neutrinos, produced in the fusion of hydrogen in the solar core, change type – or flavour – while passing through the Sun on their way to Earth. The end of an era came on 28 November 2006 when the Sudbury Neutrino Observatory (SNO) stopped data-taking after eight years of exciting discoveries. The heart of the detector, which is located 2 km underground in a cleanroom, comprises 1000 tonnes of heavy water. Artist’s impression of the Sudbury Neutrino Observatory. Arushanova, +153 authors K.In the May 2007 issue, Nick Jelley (University of Oxford) and Alan Poon (Lawrence Berkeley National Laboratory) looked back at the achievements of the SNO experiment, which helped reveal a new world of massive neutrinos. Current Status and Future Prospects of the SNO plus Experiment Status and Future Prospects of the SNO plus Experiment},Īuthor=,
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