April 2011

Construction of the lab is now complete. All of the services have been installed in all areas.The last area of the laboratory has now been given the “clean” designation and was opened for occupancy in March 2011. This means the entire lab is operating as a clean lab and brings the total lab space to about 50 000 ft2

SNO+

SNO+ will be a new kilo-tonne scale liquid scintillator detector that will study neutrinos. The heart of the SNO+ detector will be a 12m diameter acrylic sphere filled with approximately 800 tonnes of liquid scintillator which will float in a water bath. This volume will be monitored by about 10,000 photomultiplier tubes (PMTs), which are very sensitive light detectors. The acrylic sphere, PMTs and PMT support structure will be re-used from the SNO experiment. Therefore, SNO+ will look almost exactly the same as SNO except that, in addition to the ropes that currently hold the acrylic vessel up, we will add ropes to hold the vessel down once it is filled with (buoyant) scintillator. Filling of the experiment is scheduled for February 2012.

PICASSO

PICASSO has moved to its new location in one of the "Ladder - Labs" at SNOLAB. In  its new home the experiment benefits from much more available space, easier access and an improved water shielding against ambient fast neutrons. The move required a major installation and rewiring effort. PICASSO is currently operational.

COUPP

COUPP (Chicagoland Observatory for Underground Particle Physics) is looking for a nuclear recoil from a dark matter particle striking a nucleus of an atom in a liquid molecule. That triggers the evaporation of a small amount of liquid, which causes a bubble to start growing. The correct type of bubble would point to the existence of a leading candidate for dark matter called Weakly Interacting Massive Particles, or WIMPs.
A quartz jar serves as a bubble chamber and holds a liquid kept just above its normal boiling point, but under enough pressure that it will not boil unless disturbed. When a charged particle zips through the liquid, it triggers boiling along its path, visible as a series of small bubbles.
Scientists expect a dark matter particle to leave a single bubble in a particular area of the jar in contrast to the multi-bubble tracks left by many other particles. Once the bubbles reach a millimeter in size, researchers take snapshots and let the chamber sit recompressed and idle for about 30 seconds. It is then reset and ready to record another series of bubbles.

• COUPP revives and updates a technology not popular since the 1970s: the bubble chamber.
• A prototype bubble chamber was tested 330-feet underground in Chicago’s flood–control and sewers infrastructure, called the Tunnel and Reservoir Project.
• The first one-liter chamber was tested 350 feet below Fermilab in the NuMI tunnel.
• Liquid in the chamber is on the verge of boiling 80 percent of the experiment time.
• The COUPP bell jar contains iodotrifluoromethane, a fire-extinguishing liquid known as CF3I.
• COUPP can use the sound of bubbles to differentiate between potential dark matter signals background noise from common alpha particles such as radon. Bubbles give off a high-pitched “plink”, like a submarine’s sonar.

COUPP started in 2004. A 4–kilogram bubble chamber was installed at SNOLAB in September 2010. A second 60–kg chamber will follow in 2011.

HALO

HALO uses large volumes lead to watch for a supernova neutrino burst. A neutrino interaction with lead produces a free neutron which elastically scatters in the detector until it is absorbed, exits the experimental area or is captured by the neutron detectors. Neutrons captured by the 128 Helium-3 detectors produce an electronic signal. Unfortunately other types of particles such as those created by cosmic rays in the atmosphere can deposit energy in our detectors. To filter them out, HALO is located 2 km underground and shielded from externally produced neutrons with approximately 10480 litres of water.

The construction of HALO is complete with only the installation of the NCD tubes left.

DEAP-1

Dark matter Experiment with Argon and Pulse-shape discrimination
DEAP-1 uses liquid argon as both the target volume and detection medium. Argon produces 40 photons per keV of energy deposited by electrons. Thus even low-energy nuclear recoils of order 40 keV (equivalent to about 12 keV electron energy) are detectable.
DEAP-1 is currently operational at SNOLAB.

DEAP 3600

DEAP 3600 is a second generation experiment that will search for dark matter particle interactions in liquid argon. The large detector (DEAP 3600) containing a total of 3600 kg of liquid argon is being designed, with a target sensitivity to spin -independent scattering on nucleons of 10−46 cm2, several hundred times more sensiive than current dark matter searches. DEAP-3600 will be located in the Cube Hall alongside the mini-CLEAN experiment.

mini-CLEAN

SNOLAB has completed the assembly of the MiniCLEAN water shield tank in the Cube Hall. This tank is 18' in diameter and 25' tall and will be filled with water to moderate neutron and gamma backgrounds. It will also serve as a cosmic-ray muon veto once outfitted with 48 photomultiplier tubes. A second, larger tank is being assembled in the Cube Hall for the DEAP-3600 experiment for similar shielding. Once the detectors are installed in the tanks, liners will be unrolled to contain the water.

	View of the Cube Hall. The DEAP 3600 and mini-CLEAN experiments will be located in this space.
	A view of the cryopit from above.
	SNOLAB staff exploring the newly opened areas of the lab
	The HALO experiment
	Dr. Chris Jillings alongside the DEAP-1 experiment.
	Taking a break in the Lunch Room.
	The underground meeting room.
	A new purification plant is being installed to filter the Linear Alkyl Benzene that will used in the SNO+ experiment.
	The COUPP experiment
	An underground laundry facility to wash the staff's clean room clothing.
	Dr. Nigel Smith alongside the mini-CLEAN detector located in the Cube Hall.
	The PICASSO experiment in its new location in the Ladder Labs.