The Sudbury Neutrino Observatory

The Sudbury Neutrino Observatory (SNO) results have providedrevolutionary insight into the properties of neutrinos and the core of thesun. The detector, shown in the artist's conception below, was built 6800feet under ground, in VALE's Creighton minenear Sudbury, Ontario, Canada. SNO was a heavy-water Cherenkov detectordesigned to detect neutrinos produced by fusion reactions in the sun. Itused 1000 tonnes of heavy water loaned fromAtomic Energy of Canada Limited (AECL), and contained by a 12 meter diameteracrylic vessel. Neutrinos reacted with theheavy water (D₂O) to produce flashes of light called Cherenkov radiation.This light was then detected by an array of 9600 photomultiplier tubesmounted on a geodesic support structuresurrounding the heavy water vessel. The detector was immersed in light(normal) water within a 30 meter barrel-shapedcavity (the size of a 10 story building!)excavated from Norite rock. Located in the deepest part of the mine, theoverburden of rock shielded the detector from cosmic rays. The detectorlaboratory, still functioning as part of the newSNOLAB facility, is extremely clean toreduce background signals from radioactive elements present in the mine dustwhich would otherwise hide the very weak signal from neutrinos.Plans arecurrently underway to upgrade the SNO detector for the newSNO+ experiment.

The first co-spokesmen for the SNO collaboration when it was established in 1984 were Professor Herb Chen from U California, Irvine and Professor George Ewan, Queen’s University.For interesting accounts of the early development work for the SNO experiment, please see:
"Early Development of the Underground SNO Laboratory in Canada" and"The Funding Campaign for the Sudbury Neutrino Observatory", G.T. Ewan and W.F. Davidson, Physics in Canada, Vol. 61, No. 6 (2005), p. 339-346 and 347-350. (download in PDF format)

For a review article summarizing the three phases of the SNO experiment, please see:
"The Sudbury Neutrino Observatory", Nick Jelley, Arthur B. McDonald, and R.G. Hamish Robertson, Annu. Rev. Nucl. Part. Sci. 2009.59:431-465. (download in PDF format)

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In Memoriam: Andre Hamer 1968-2003

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• NCD-phase SNO-only chi-squared map for the neutrinomixing-parameter analysis [Phys. Rev. Lett. 101, 111301 (2008)]
• Salt-phase SNO-only chi-squared map for the neutrinomixing-parameter analysis [Phys. Rev. C72, 055502 (2005)]

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SNO Web Sites at Participating Institutions

Present Status

• June 5, 2008: SNO publishes NCD-phase results (downloadPDF).
• May 28, 2007: Heavy water completely drained from acrylic vessel.
• November 28, 2006: End of data aquisition with NCD's and heavy water.
• February 28, 2005: SNO publishes 391-day salt-phase results (downloadPDF, Postscript orfigures).
• January 2005: Production data taking with NCD array installed.
• April 21, 2004: NCD testing and repairing is complete and the ROV is removed from the detector.
• February 12, 2004: The NCD's are all installed and we begin the third phase of detector operation.
• September 2003: Salt is removed from the heavy water
• September 7, 2003: SNO releases Salt Phase Results.
• May 2003: NCD pre-deployment welding has just been completed.NCD deployment is scheduled for August.
• June 20, 2002: The International Facility for Underground Science receives funding
• April 20, 2002: New scientific results released.
• June 2001: SNO releases its First Scientific Results on Monday, Jun 18 at 12:15 EDT.
• May 2001: Salt has been added to the heavy water to enhance the neutral current efficiency.Thismarks the beginning of the second phase of detector operation.
• June 2000: SNO presentations at Neutrino 2000give the current detector status.
• November 1999: Detector parameters frozen.Start of production data taking.

The Sudbury Neutrino Observatory Institute (SNOI):

For general information email: snoinfo@surf.sno.laurentian.ca

URL: https://www.sno.phy.queensu.ca/sno/ (Last revised Nov 9, 2015)
(Mail problems/comments to qusno@sno.phy.queensu.ca)