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Queen's Particle Astrophysics - Projects


^ SNOLAB (home page, contact)

Deep underground laboratory for particle astrophysics

We have built a new, deep underground laboratory called SNOLAB, 6800 feet underground at the SNO site near Sudbury. This facility will host a battery of new experiments to address several unanswered questions about the properties of neutrinos, and the nature dark matter and dark energy, and how these relate to the origins of our universe. The underground laboratory is necessary to look for the rare events that are signals for the neutrino and dark matter interactions that are used to probe the cosmos.

Below are summaries of the different Queen's astroparticle experiments, many of which take advantage of the SNOLAB facilities. See the individual project home pages for more details and references to published papers.

Click here to see a video of SNOLAB


^ SNO (home page, contact)

The Sudbury Neutrino Observatory

The SNO experiment was designed to look at neutrinos from the sun and led to the discovery that neutrinos change flavour in passing from the core of the sun to the earth.

Although SNO data acquisition stopped in November, 2006, data analysis has continued and is nearly complete after the publication of several papers extending the work on solar and atmospheric neutrinos.

Neutrinos may be the most common particle in the universe, yet they are also among the most difficult to detect. The majority of neutrinos detected here on earth are produced in the Sun by stellar burning processes (about 2% of the total energy from the sun is emitted in the form of neutrinos), however they can also be the result of radioactive decay, supernova explosions (where 99% of the released energy is in the form of neutrinos), or as relics from the big bang.

The SNO detector observed tiny flashes of light resulting from neutrino interactions using an array of 9600 20cm-diameter photomultiplier tubes (PMTs) each of which are sensitive to single photons. At the core of the detector was 1000 tonnes of heavy water which was used to detect neutrinos via three different nuclear interactions. Through careful analysis, these measurements provide insight into previously unknown properties of this elusive particle.


^ PICO (home page, contact)

Dark matter search with superheated droplets

PICO is a direct dark matter search experiment. It uses the superheated droplet detector technique to find evidence for dark matter in our solar system. The experiment is located at SNOLAB in Sudbury, Ontario. The Queen's group is involved in the design, installation, and operation of the system. Queen's students are also at the forefront of the data analysis of PICO WIMP search data.

Supersymmetry theories favored by particle physicists today predict the existence of a stable heavy particle that only interacts weakly. These particles are called WIMPs (weakly interacting massive particles).

PICO uses tiny (200μm) liquid droplets of freon suspended in a gel as medium for detecting these WIMPs. The droplets are kept in a superheated state, and when a WIMP hits a droplet the freon changes phase to a gaseous bubble. This transition creates a shock wave that is detected by a piezo-electric sensor.

A single detector has 9 piezo-electric sensors and contains 4.5 litres of gel. The detectors are housed in a temperature-controlled enclosure and surrounded with water shielding to reduce background radiation. Currently, 29 detectors are operational at SNOLAB, with plans to add 3 more.


^ SNO+ (home page, contact)

Liquid scintillator detector for low energy neutrinos

SNO+ is a project that is a follow-up to SNO. Using most of the existing SNO detector but replacing the heavy water with a "new" liquid scintillator made from linear alkylbenzene, SNO+ would be sensitive to solar neutrinos with lower energies than SNO, and it would also be able to detect antineutrinos produced by nuclear reactors and by the decays of the natural radioisotopes present in the Earth. This would give SNO+ the ability to make measurements that are important not only to neutrino physics, but also to solar physics, geophysics and geochemistry.

By measuring the survival probability of the pep solar neutrinos with precision, SNO+ would probe the coupling between neutrinos and matter in the region most sensitive to new phenomena. This could reveal the presence of new physics such as non-standard couplings to new particles, or the presence of sub-dominant effects in oscillations from a sterile neutrino.

We can load the liquid scintillator with Tellurium, a double beta decay isotope. With tonnes of Tellurium dispersed in the detector, SNO+ could detect neutrino-less double beta decay. This would shed light on the charge conjugation nature of the neutrino and on the absolute neutrino mass scale, both impacting on our understanding of the evolution of the Universe.

Queen's is one of the leaders in developing this project. The SNO+ Project Director is Queen's Faculty member Professor Mark Chen. Mechanical construction during the transition, scintillator purification, liquid scintillator optics, double beta decay, calibration sources and hardware, detector and physics simulations and analysis - there are opportunities to get involved in many aspects of this project.


^ DEAP (contact)

Dark matter search with liquid argon

With DEAP-1 with 7 kg of liquid argon, we have demonstrated a discrimination of events that are backgrounds to the dark matter search (beta and gamma events) in liquid argon at the level of 10-8. With this very low background level, the 3600 kg DEAP-3600 detector is projected to be sensitive to cross-sections down to 10-46cm2, and will increase the current experimental sensitivity to dark matter particles by a substantial factor.

Construction of the DEAP-3600 detector underground at SNOLAB (pictured) is complete and the detector is currently taking data. The DEAP group at Queen's is active in cryogenics design and construction, liquid argon purification and scintillation studies, Monte-Carlo simulation, detector calibration and analysis.


^ SuperCDMS (home page, contact)

SuperCDMS Dark matter search with cryogenic detectors

The Cryogenic Dark Matter Search (CDMS) collaboration has develope cryogenic semiconductor detectors to detect and identify the very rare interactions of Weakly Interacting massive Paricles (WIMPs) - proposed to solve the long standing dark matter problem - with atomic nuclei. The detectors are kept at very low temperatures (40-50 mK) so the low energy of a WIMP interaction still can cause a measurable increase in the detector temperature. With the additional detection of an ionization signal from each interaction, these detectors become very powerful in discriminating between ordinary radiation such as environmental radioactivity and potential WIMP interactions.

SuperCDMS, the successor of CDMS is presently operating cryogenic germanium detectors with a total mass of roughly 9 kg at the Soudan Underground Laboratory in Minnesota. At the same time we are preparing for the next phase of the experiment which aims at deploying detectors with a total mass of hundreds of kilogram at sNOLAB. The main reason for moving to SNOLAB is the considerably better shielding against cosmogenic radiation due to the larger depth of the laboratory.

At Queen's we operate a cryogenic facility for detector R&D, and characterization and testing of the new detectors being developed and produced for SuperCDMS SNOLAB. We are also heavily invovled in data analysis and Monte Carlo simulations. Queen's will paly a leading role for the installation of the new setup at SNOLAB.


^ NEWS (home page, contact)

New Experiments With Spheres

A large collaboration, led by Queen's Faculty member Professor Gilles Gerbier, now seeks to build a 1.4 m diameter spherical detector, within an 8 m diameter tank filled with ultra pure water. This is to increase the physics reach in the GeV and sub-GeV mass range, thanks in particular to the use of very light nuclei targets like He and H from CH4 or other H rich gas. The ideal location for operation is SNOLAB, the second deepest and the cleanest underground laboratory in the world.

Specific features of this kind of detectors -- low capacitance, low threshold, excellent energy resolution, single readout channel in its simplest version, low cost, robustness, flexibility in gas choice, in operating pressure -- have led to envisage various applications ranging from Dark Matter detection, Coherent Nuclear Neutrino Scattering study, Double Beta decay search to gamma ray and neutron spectroscopy.

If you have questions or comments about the content of this website, please contact qusno@sno.phy.queensu.ca.