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Neutrinos and Dark Matter

HALO development

HALO development: The HALO supernova neutrino detector in SNOLAB is unique among neutrino detectors in that it is primarily sensitive to electron-type neutrinos, rather than electron-type antineutrinos.  As such, it has an important role to play in understanding the neutrino flavour content of the neutrino burst from the next galactic core-collapse supernova. The period 2013-2018 had several highlights for HALO:
  1. The completion of the construction of the HALO detector and its water shielding
  2. The calibration of the detector with a neutron source inserted at multiple locations within the lead matrix
  3. HALO joining the international SuperNova Early Warning System (SNEWS) in October 2015
The HALO collaboration has recently expanded to become the HALO-1kT collaboration, to include new collaborators from the USA and Italy. The collaboration is currently designing a much larger detector, using the 1000 tonnes of lead from the decommissioned OPERA detector at the Gran Sasso laboratory in Italy, and making plans to measure the neutrino-lead cross section at the Spallation Neutron Source at Oak Ridge National Laboratory, Tennessee. TRIUMF's role in the construction of the detector: TRIUMF's electronics shop fabricated the electrical cables that supply the neutron detectors with high voltage, and carry the signals from the neutron detectors to the amplifiers and then onto the data acquisition computers. TRIUMF's machine shop built the test stand that was used to test the neutron detectors one by one before installation inside the lead matrix of HALO. A substantial part of the manpower for design and assembly of the detector was supplied by TRIUMF. TRIUMF's role in the calibration of the detector: The neutron detectors count the number of neutrons emitted when supernova neutrinos hit the mass of lead. But not all neutrons are counted; some are absorbed by the lead itself, and others escape out the surface of the lead mass. To relate the number of neutrinos arriving from the supernova to the number of neutrons counted, it is necessary to know the efficiency with which neutrons are counted.  We do this by inserted a radioactive source that injects a known number of neutrons at various locations in the lead matrix, and compare this with the number of neutrons that are counted).