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33-563: The detector was turned on in May 1999, and was turned off on 28 November 2006. The SNO collaboration was active for several years after that analyzing the data taken. The director of the experiment, Art McDonald , was co-awarded the Nobel Prize in Physics in 2015 for the experiment's contribution to the discovery of neutrino oscillation . The underground laboratory has been enlarged into

66-531: A B.Sc. in physics in 1964 and M.Sc. in physics in 1965 from Dalhousie University in Nova Scotia . He then obtained his Ph.D. in physics in 1969 from the California Institute of Technology . McDonald cited a high school math teacher and his first-year physics professor at Dalhousie as his inspirations for going into the field of physics. Art McDonald worked as a research officer at

99-456: A collaborating institution, Chalk River Laboratories led the construction of the acrylic vessel that holds the heavy water, and Atomic Energy of Canada Limited was the source of the heavy water. 46°28′30″N 81°12′04″W  /  46.47500°N 81.20111°W  / 46.47500; -81.20111 Arthur B. McDonald Arthur Bruce McDonald , CC OOnt ONS FRS FRSC P.Eng (born August 29, 1943)

132-496: A detector for solar neutrinos. Unlike previous detectors, using heavy water would make the detector sensitive to two reactions, one reaction sensitive to all neutrino flavours, the other sensitive to only the electron neutrino. Thus, such a detector could measure neutrino oscillations directly. Chen, Professor George Ewan, Professor David Sinclair, McDonald, and 12 other scientists formed the original Sudbury Neutrino Observatory (SNO) collaboration to exploit this idea in 1984. SNO

165-640: A leader in astroparticle physics. In the spring of 2020, amid the COVID-19 pandemic and the ensuing shortages, McDonald became one of the leaders of a project to mass-produce mechanical ventilators at low cost. McDonald has stated that the project was initiated by Princeton Professor Cristiano Galbiati who was locked down in Milan , Italy. He inspired action by his colleagues on the DarkSide-20k Dark Matter physics experiment after recognizing

198-623: A permanent facility and now operates multiple experiments as SNOLAB . The SNO equipment itself was being refurbished as of February 2017 for use in the SNO+ experiment. The first measurements of the number of solar neutrinos reaching the Earth were taken in the 1960s, and all experiments prior to SNO observed a third to a half fewer neutrinos than were predicted by the Standard Solar Model . As several experiments confirmed this deficit

231-402: A small cross section for neutrons, but when neutrons are captured by a deuterium nucleus, a gamma ray ( photon ) with roughly 6 MeV of energy is produced. The direction of the gamma ray is completely uncorrelated with the direction of the neutrino. Some of the neutrons produced from the dissociated deuterons make their way through the acrylic vessel into the light water jacket surrounding

264-573: A supernova are released earlier than the photons, it is possible to alert the astronomical community before the supernova is visible. SNO was a founding member of the Supernova Early Warning System (SNEWS) with Super-Kamiokande and the Large Volume Detector . No such supernovae have yet been detected. The SNO experiment was also able to observe atmospheric neutrinos produced by cosmic ray interactions in

297-767: Is a Canadian astrophysicist . McDonald is the director of the Sudbury Neutrino Observatory Collaboration and held the Gordon and Patricia Gray Chair in Particle Astrophysics at Queen's University in Kingston, Ontario from 2006 to 2013. He was awarded the 2015 Nobel Prize in Physics jointly with Japanese physicist Takaaki Kajita . Art McDonald was born on August 29, 1943, in Sydney , Nova Scotia . He graduated with

330-691: Is a co-recipient of the 2007 Benjamin Franklin Medal in Physics, the 2015 Nobel Prize in Physics , and the Breakthrough Prize in Fundamental Physics in 2016 for the discovery of neutrino oscillations and demonstrating that neutrinos have mass. Professor McDonald is now participating in research with the SNO+ and DEAP-3600 experiments at SNOLAB, an expanded underground laboratory at the original SNO underground site and with

363-553: Is detectable. The proton which is produced does not have enough energy to be detected easily. The electrons produced in this reaction are emitted in all directions, but there is a slight tendency for them to point back in the direction from which the neutrino came. In the neutral current interaction, a neutrino dissociates the deuteron, breaking it into its constituent neutron and proton. The neutrino continues on with slightly less energy, and all three neutrino flavours are equally likely to participate in this interaction. Heavy water has

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396-474: Is dominated by electron neutrinos, and this is the channel through which the Super-Kamiokande (Super-K) detector can observe solar neutrinos. This interaction is the relativistic equivalent of billiards , and for this reason the electrons produced usually point in the direction that the neutrino was travelling (away from the sun). Because this interaction takes place on atomic electrons it occurs with

429-427: Is located at the end of a 1.5-kilometre-long (0.9 mi) drift , named the "SNO drift", isolating it from other mining operations. Along the drift are a number of operations and equipment rooms, all held in a clean room setting. Most of the facility is Class 3000 (fewer than 3,000 particles of 1 μm or larger per 1 ft of air) but the final cavity containing the detector is an even stricter Class 100 . In

462-854: The Chalk River Nuclear Laboratories northwest of Ottawa from 1969 to 1982. He became professor of physics at Princeton University from 1982 to 1989, leaving Princeton to join Queen's University where he was a professor from 1989 to 2013. McDonald was a visiting scientist at the European Organization for Nuclear Research (CERN) in Geneva in 2004. In 2013 McDonald became a professor emeritus of Queen's University in Kingston, Canada . He continues to be active in basic research in Neutrinos and Dark Matter at

495-552: The SNOLAB underground Laboratory and was a past member of the board of the Perimeter Institute for Theoretical Physics . His visiting positions include CERN , University of Washington (1978), Los Alamos National Laboratory (1981), University of Hawaii (2004, 2009), University of Oxford (2003, 2009), Queen's University (1988). Physicists have been investigating whether or not neutrinos have mass. Since

528-533: The University of California at Irvine first pointed out the advantages of using heavy water as a detector for solar neutrinos. Unlike previous detectors, using heavy water would make the detector sensitive to two reactions, one reaction sensitive to all neutrino flavours, the other reaction sensitive to only electron neutrino. Thus, such a detector could measure neutrino oscillations directly. A location in Canada

561-413: The charged current interaction, a neutrino converts the neutron in a deuteron to a proton . The neutrino is absorbed in the reaction and an electron is produced. Solar neutrinos have energies smaller than the mass of muons and tau leptons , so only electron neutrinos can participate in this reaction. The emitted electron carries off most of the neutrino's energy, on the order of 5–15  MeV , and

594-665: The DarkSide-20k collaboration developing an experiment at the underground laboratory near Gran Sasso , Italy. The Arthur B. McDonald Canadian Astroparticle Physics Research Institute was inaugurally named the Canadian Particle Astrophysics Research Centre before renaming itself the Arthur B. McDonald Canadian Astroparticle Physics Research Institute in May 2018, in recognition of Dr. Arthur B. McDonald's trailblazing work making Canada

627-426: The accelerated electron can be detected through Cherenkov radiation. In the elastic scattering interaction, a neutrino collides with an atomic electron and imparts some of its energy to the electron. All three neutrinos can participate in this interaction through the exchange of the neutral Z boson , and electron neutrinos can also participate with the exchange of a charged W boson . For this reason this interaction

660-482: The atmosphere. Due to the limited size of the SNO detector in comparison with Super-K, the low cosmic ray neutrino signal is not statistically significant at neutrino energies below 1  GeV . Large particle physics experiments require large collaborations. With approximately 100 collaborators, SNO was a rather small group compared to collider experiments . The participating institutions have included: Although no longer

693-610: The director of SNO Art McDonald with the Benjamin Franklin Medal in Physics. In 2015 the Nobel Prize for Physics was jointly awarded to Arthur B. McDonald, and Takaaki Kajita of the University of Tokyo, for the discovery of neutrino oscillations. The SNO detector would have been capable of detecting a supernova within our galaxy if one had occurred while the detector was online. As neutrinos emitted by

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726-416: The effect became known as the solar neutrino problem . Over several decades many ideas were put forward to try to explain the effect, one of which was the hypothesis of neutrino oscillations . All of the solar neutrino detectors prior to SNO had been sensitive primarily or exclusively to electron neutrinos and yielded little to no information on muon neutrinos and tau neutrinos . In 1984, Herb Chen of

759-446: The heavy water, and since light water has a very large cross section for neutron capture, these neutrons are captured very quickly. Gamma rays of roughly 2.2 MeV are produced in this reaction, but because the energy of the photons is less than the detector's energy threshold (meaning they do not trigger the photomultipliers), they are not directly observable. However, when the gamma ray collides with an electron via Compton scattering,

792-530: The late 1960s, experiments have hinted that neutrinos may have mass. Theoretical models of the Sun predict that neutrinos should be made in large numbers. Neutrino detectors on the Earth have repeatedly seen fewer than the expected number of neutrinos. Because neutrinos come in three varieties (electron, muon, and tau neutrinos), and because solar neutrino detectors have been primarily sensitive only to electron neutrinos,

825-447: The mine management was willing to make the location available for only incremental costs. The SNO collaboration held its first meeting in 1984. At the time it competed with TRIUMF 's KAON Factory proposal for federal funding, and the wide variety of universities backing SNO quickly led to it being selected for development. The official go-ahead was given in 1990. The experiment observed the light produced by relativistic electrons in

858-547: The precision of the original result. Although Super-K had beaten SNO to the punch, having published evidence for neutrino oscillation as early as 1998, the Super-K results were not conclusive and did not specifically deal with solar neutrinos. SNO's results were the first to directly demonstrate oscillations in solar neutrinos. This was important to the standard solar model . In 2007, the Franklin Institute awarded

891-412: The preferred explanation over the years is that those "missing" neutrinos had changed, or oscillated, into a variety for which the detectors had little or no sensitivity. If a neutrino oscillates , according to the laws of quantum mechanics , then it must have a mass. In 1984, McDonald's collaborator Herb Chen at the University of California at Irvine suggested the advantages of using heavy water as

924-555: The same rate in both the heavy and light water. The first scientific results of SNO were published on 18 June 2001, and presented the first clear evidence that neutrinos oscillate (i.e. that they can transmute into one another), as they travel from the Sun. This oscillation, in turn, implies that neutrinos have non-zero masses. The total flux of all neutrino flavours measured by SNO agrees well with theoretical predictions. Further measurements carried out by SNO have since confirmed and improved

957-929: The similarities between the requirements of a ventilator and those of particle physics experiments. McDonald led the Canadian team with members from TRIUMF laboratory, CNL Chalk River, SNOLAB and the McDonald Canadian Astroparticle Physics Research Institute after strong positive response from the Directors of these institutions. The design, called the Mechanical Ventilator Milano, is based on the Manley ventilator but uses modern electronics wherever possible. The details, first published on March 23 by about 150 collaborators, were released under

990-457: The vessel was filled with normal water to provide both buoyancy for the vessel and radiation shielding . The heavy water was viewed by approximately 9,600 photomultiplier tubes (PMTs) mounted on a geodesic sphere at a radius of about 850 centimetres (28 ft). The cavity housing the detector was the largest in the world at such a depth, requiring a variety of high-performance rock bolting techniques to prevent rock bursts. The observatory

1023-459: The water created by neutrino interactions. As relativistic electrons travel through a medium, they lose energy producing a cone of blue light through the Cherenkov effect , and it is this light that is directly detected. The SNO detector target consisted of 1,000 tonnes (1,102 short tons ) of heavy water contained in a 6-metre-radius (20 ft) acrylic vessel. The detector cavity outside

Sudbury Neutrino Observatory - Misplaced Pages Continue

1056-531: Was attractive because Atomic Energy of Canada Limited , which maintains large stockpiles of heavy water to support its CANDU reactor power plants, was willing to lend the necessary amount (worth CA$ 330,000,000 at market prices) at no cost. The Creighton Mine in Sudbury is among the deepest in the world and, accordingly, experiences a very small background flux of radiation. It was quickly identified as an ideal place for Chen's proposed experiment to be built, and

1089-548: Was to be a detector facility using 1000 tonnes of heavy water located 6,800 feet (2,100 m) underground in a mine outside Sudbury, Ontario. Chen died of leukemia in November 1987, however. In August 2001, the Sudbury Neutrino Observatory , led by McDonald since 1989, reported observations that directly suggested electron neutrinos from the Sun were oscillating into muon and tau neutrinos. McDonald

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