SNOLAB surface building. Access to the underground facilities is provided via the nearby mine elevator operated byVale Limited
SNOLAB is the world's deepest operational clean room facility. Although accessed through an active mine, the laboratory proper is maintained as a class-2000cleanroom, with very low levels ofdust andbackground radiation. SNOLAB's 2070 m (6800 feet) of overburden rock provides 6010metre water equivalent (MWE) shielding from cosmic rays, providing a low-background environment for experiments requiring highsensitivities and extremely low countingrates.[1] The combination of great depth and cleanliness that SNOLAB affords allows extremely rare interactions and weak processes to be studied. In addition to neutrino and dark matter physics, SNOLAB is also host to biological experiments in an underground environment.
The Sudbury Neutrino Observatory was the world's deepest underground experiment since theKolar Gold Fields experiments ended with the closing of that mine in 1992.[2] Many research collaborations were, and still are, interested in conducting experiments in the 6000 MWE location.
In 2002, funding was approved by theCanada Foundation for Innovation to expand the SNO facilities into a general-purpose laboratory,[3] and more funding was received in 2007[4] and 2008.[5]
Construction of the major laboratory space was completed in 2009,[6] with the entire lab entering operation as a 'clean' space in March 2011.[7]
SNOLAB is the world's deepest underground laboratory, tied with theChina Jinping Underground Laboratory since 2011. Although CJPL has more rock (2.4 km) above it, the effective depth for science purposes is determined by the cosmic ray muon flux, and CJPL's mountain location admits more muons from the side than SNOLAB's flatoverburden. The measured muon fluxes are0.27 μ/m²/day (3.1×10−10 μ/cm²/s) at SNOLAB,[1][better source needed] and0.305±0.020 μ/m²/day ((3.53±0.23)×10−10 μ/cm²/s) at CJPL,[8] tied to within the measurement uncertainty. (For comparison, the rate on the surface, at sea level, is about 15 million μ/m²/day.)
CJPL does have the advantage of fewer radioisotopes in the surrounding rock.
CVMR (Chemical Vapour Metal Refining) played a significant role in the development of theSudbury Neutrino Observatory (SNO) by supplying approximately 1,200 nickel tubes manufactured using the chemical vapour deposition (CVD) process. According to the company’s official documentation[9], this method produced ultra-high-purity nickel with extremely low concentrations of radioactive impurities such as uranium and thorium, which was essential for the performance of SNO’s highly sensitive neutron detectors. Studies on the project confirm that the use of CVD nickel reduced radioactive contaminants by up to six orders of magnitude, ensuring the required radiopurity for neutrino measurements[10]. The tubes supplied by CVMR formed the basis of the proportional neutron detectors (NCDs), contributing significantly to the observatory’s scientific success.
SNO+ is aneutrino experiment using the original SNO experiment chamber, but using liquid scintillator in the place of heavy water from SNO.Linear alkyl benzene, the scintillator, increases the light yield, and therefore the sensitivity, allowing SNO+ to detect not only solar neutrinos, but also geoneutrinos, and reactor neutrinos. The ultimate goal of SNO+ is to observeneutrinoless double beta decay (0vbb). A 2023 paper has also demonstrated its ability to monitor nuclear reactors.[15]
HALO (Helium and Lead Observatory) is a neutron detector using ring-shaped lead blocks to detect neutrinos fromsupernovae within our galaxy.[16][17] HALO is part of the Supernova Early Warning System (SNEWS), an international collaboration of neutrino-sensitive detectors that will allow astronomers the opportunity to observe the first photons visible following a core-collapse supernova.[18]
DAMIC – Dark Matter in Charged Coupled Devices (CCDs) – adark matter detector using unusually thick CCDs to take long exposure images of particles passing through the detector. Various particles have known signatures and DAMIC seeks to find something new that could signal dark matter particles.[19][20][21][22]\
DEAP-3600 – Dark Matter Experiment using Argon Pulse-shape Discrimination – is a second generation dark matter detector, using 3600 kg of liquid argon. This experiment aims to detectWIMP-like dark matter particles through argon scintillation, producing small amounts of light that is detected by extremely sensitivephotomultiplier tubes.[23][24][25]
The PICO 40L, a third generationbubble chamber dark matter search experiment,[12][26] is a merger of the formerPICASSO and COUPP collaborations.[27][28] PICO operates using superheated fluids which form small bubbles when energy is deposited by particle interactions. These bubbles are then detected by high speed cameras and extremely sensitive microphones.[29]
NEWS-G – New Experiments with Spheres–Gas – is a second generation spherical proportional counter electrostatic dark matter detector usingnoble gases in their gaseous state, as opposed to liquid noble gases used in DEAP-3600 and miniCLEAN. The original NEWS experiment is at theLaboratoire Souterrain de Modane.[30][31]
FLAME – Flies in A Mine Experiment – a biological experiment using fruit flies as a model organism to investigate the physical responses to working in increased atmospheric pressure underground.[32]
REPAIR – Researching the Effects of the Presence and Absence of Ionizing Radiation – a biological experiment investigating the effects of low background radiation on growth, development, and cellular repair mechanisms.[33]
SuperCDMS – Super-Cryogenic Dark Matter Search – is a second generation dark matter detector using silicon and germanium crystals cooled down to 10 mK, a fraction of a degree aboveabsolute zero. This experiment aims to detect low mass dark matter particles through very small energy deposition in the crystal from particle collisions, resulting in vibrations detected by sensors.[34][35][36][37]
PICO-500 is the next generation detector that builds upon the principle demonstrated by PICO-2L, −60, and −40L. PICO-500 will have an active volume of about 250 litres and will use a synthetic quartz vessel, just like versions before it. The PICO collaboration completed the design and is in the process of assembling and constructing the detector in SNOLAB's Cube Hall. PICO is planning to operate PICO-500 with C3F8 to achieve a world leading sensitivity for dark matter coupling to ordinary matter though its spin.
Additional planned experiments have requested laboratory space such as the next-generationnEXO,[44][45][26][46][27] and the LEGEND-1000[47][48] searches for neutrinolessdouble beta decay.[41][43] There are also plans for a larger PICO-500L detector.[49] In 2024, SNOLAB announced plans to host its firstquantum computing experiment which will investigate the performance of superconducting qubits when shielded from cosmic rays.[50]
The total size of the SNOLAB underground facilities, including utility spaces and personnel spaces, is:[51][52]
^"SNOLAB Updates April 2011". Archived fromthe original on 2011-07-06. Retrieved2011-07-11.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.
^Neilson, Russell (2013-12-16).COUPP/PICO Status Report(PDF).Fermilab All Experimenters Meeting. p. 7. Retrieved2015-12-03.COUPP and PICASSO have merged to form the PICO collaboration to search for dark matter with superheated liquid detectors.
^Saab, Tarek (2012-08-01)."The SuperCDMS Dark Matter Search"(PDF).SLAC Summer Institute 2012. SLAC National Accelerator Laboratory. Archived fromthe original(PDF) on 2014-10-29. Retrieved2012-11-28.
