SNOLAB

SNOLAB is a Canadian underground science laboratory specializing in neutrino and dark matter physics. Located 2 km below the surface in Vale's Creighton nickel mine near Sudbury, Ontario, SNOLAB is an expansion of the existing facilities constructed for the original Sudbury Neutrino Observatory (SNO) solar neutrino experiment.

SNOLAB surface building. Access to the underground facilities is provided via the nearby mine elevator operated by Vale 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-2000 cleanroom, with very low levels of dust and background radiation. SNOLAB's 2070 m (6800 feet) of overburden rock provides 6010 metre water equivalent (MWE) shielding from cosmic rays, providing a low-background environment for experiments requiring high sensitivities and extremely low counting rates.[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.

History

The Sudbury Neutrino Observatory was the world's deepest underground experiment since the Kolar Gold Fields experiments ended with the closing of that mine in 1992.[2] With the deepest underground laboratory in North America at 2100 metre water equivalent depth, and the deepest in the world at 4800 MWE, many other groups were interested in conducting experiments in the 6000 MWE location.

In 2002, funding was approved by the Canada 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 the China 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 flat overburden. The measured muon fluxes are 0.27 μ/m²/day (3.1×10−10 μ/cm²/s) at SNOLAB,[1] and 0.305±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.

Experiments

As of November 2019, SNOLAB hosts the following experiments:[9][10][3][11][12]

Neutrino detectors
  • SNO+ experiment is a neutrino 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 observe neutrinoless double beta decay (0vbb).
  • HALO (Helium and Lead Observatory) is a neutron detector using ring-shaped lead blocks to detect neutrinos from supernovae within our galaxy.[13][14] 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.[15]

Dark matter detectors
  • DAMIC - Dark Matter in Charged Coupled Devices (CCDs) – a dark 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.[16][17][18][19]
  • 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 detect WIMP-like dark matter particles through argon scintillation, or small amounts of light detected by extremely sensitive photomultiplier tubes.[20][21][22]
  • The PICO 40L, a third generation bubble chamber dark matter search experiment,[10][23] is a merger of the former PICASSO and COUPP collaborations.[24][25] 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.[26]

Biological experiments
  • 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.[27]
  • 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.[28]

Projects under construction
  • 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 above absolute 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.[29][30][31][32]
  • NEWS-G - New Experiments with Spheres–Gas – is a second generation spherical proportional counter electrostatic dark matter detector using noble gases in their gaseous state, as opposed to liquid noble gases used in DEAP-3600 and miniCLEAN. The original NEWS experiment is at the Laboratoire Souterrain de Modane.[33][34]

Decommissioned experiments

Future projects

Additional planned experiments have requested laboratory space such as the next-generation nEXO,[41][42][23][43][24] and the COBRA Experiment searches for neutrinoless double beta decay.[38][40] There are also plans for a larger PICO-500L detector.[44]

The total size of the SNOLAB underground facilities, including utility spaces and personnel spaces, is:[45][46]

ExcavatedClean roomLaboratory
Floor space 7,215 m²
77,636 ft²		4,942 m²
53,180 ft²		3,055 m²
32,877 ft²
Volume 46,648 m³
1,647,134 ft³		37,241 m³
1,314,973 ft³		29,555 m³
1,043,579 ft³

References
  1. SNOLAB User's Handbook Rev. 2 (PDF), 2006-06-26, p. 13, retrieved 2013-02-01
  2. Mondal, Naba K. (January 2004). "Status of India-based Neutrino Observatory (INO)" (PDF). Proceedings of the Indian National Science Academy. 70 (1): 71–77. Retrieved 2007-08-28.
  3. "Canada selects 9 projects to lead in international research" (Press release). Canada Foundation for Innovation. 2002-06-20. Retrieved 2007-09-21.
  4. "Province Supports Expansion of World's Deepest Lab Administered by Carleton University" (Press release). Carleton University. 2007-08-21. Retrieved 2007-09-21.
  5. "New Funding will Support Underground Lab Operations as SNOLAB nears Completion" (PDF) (Press release). SNOLAB. 2008-01-18. Retrieved 2008-02-26.
  6. Duncan, Fraser (2009-08-27). "SNOLAB Facility Status" (PDF).
  7. "SNOLAB Updates April 2011". Archived from the original on 2011-07-06. Retrieved 2011-07-11. 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.
  8. Gui, Zuyi; et al. (JNE collaboration) (13 Oct 2020). "Muon Flux Measurement at China Jinping Underground Laboratory". Chinese Physics C. arXiv:2007.15925. doi:10.1088/1674-1137/abccae. S2CID 220920141. (Chinese Physics C, to appear)
  9. SNOLAB: Current experiments
  10. Noble, Tony (2014-01-31). Dark Matter Physics at SNOLAB and Future Prospects (PDF). Fourth International Workshop for the Design of the ANDES Underground Laboratory.
  11. Duncan, Fraser (2015-08-24). Overview of the SNOLAB Facility and Current Programme Evolution (PDF). SNOLAB Future Planning Workshop 2015. Retrieved 2015-12-03.
  12. Jillings, Chris (9 September 2015). The SNOLAB science program (PDF). XIV International Conference on Topics in Astroparticle and Underground Physics (TAUP2015). Torino. Retrieved 2015-11-30.
  13. HALO, 2012, retrieved 2019-11-14
  14. Helium and Lead Observatory, 2012, retrieved 2019-11-14
  15. SNEWS: Supernova Early Warning System, 2012, retrieved 2019-11-14
  16. DAMIC, 2012, retrieved 2019-11-15
  17. DAMIC Overview . (PDF), 2016-09-01, retrieved 2019-11-15
  18. DAMIC now running at SNOLAB, 2019-07-29, retrieved 2019-11-06
  19. Cancelo, Gustavo (2014-01-31). The DAMIC experiment (PDF). Fourth International Workshop for the Design of the ANDES Underground Laboratory.
  20. Field, Louisa (23 April 2015). "Biggest dark matter detector lies in wait for antisocial WIMPs". New Scientist (3108). At the end of April, it will join other underground detectors worldwide in the race to find dark matter.
  21. DEAP, 2012, retrieved 2019-11-15
  22. DEAP-3600 Detector, 2012-11-01, retrieved 2019-11-15
  23. "PICO: Searching for dark matter with superheated fluids". 2019-07-29.
  24. Crisler, Michael B. (21 August 2013). PICO 250-liter Bubble Chamber Dark Matter Experiment (PDF). SNOLAB Future Projects Planning Workshop 2013. p. 3. Retrieved 2015-12-03. PICASSO + COUPP = PICO
  25. Neilson, Russell (2013-12-16). COUPP/PICO Status Report (PDF). Fermilab All Experimenters Meeting. p. 7. Retrieved 2015-12-03. COUPP and PICASSO have merged to form the PICO collaboration to search for dark matter with superheated liquid detectors.
  26. PICO: Searching for dark matter with superheated liquids, 2019-07-29, retrieved 2019-11-15
  27. FLAME, 2012, retrieved 2019-11-15
  28. REPAIR, 2012, retrieved 2019-11-15
  29. "Second generation dark matter experiment coming to SNOLAB" (Press release). SNOLAB. 2014-07-18. Retrieved 2014-09-18.
  30. Saab, Tarek (2012-08-01). "The SuperCDMS Dark Matter Search" (PDF). SLAC Summer Institute 2012. SLAC National Accelerator Laboratory. Retrieved 2012-11-28.
  31. Construction Begins on One of the World's Most Sensitive Dark Matter Experiments, 2018-05-07, retrieved 2019-11-15
  32. Rau, Wolfgang (2016-09-01), SuperCDMS at SNOLAB (PDF), retrieved 2019-11-15
  33. NEWS, 2012, retrieved 2019-11-15
  34. New Experiments with Spheres-Gas, 2019, retrieved 2019-11-15
  35. "COUPP Experiment - E961".
  36. Science at SNOLAB
  37. Behnke, E.; Behnke, J.; Brice, S.J.; Broemmelsiek, D.; Collar, J.I.; Conner, A.; Cooper, P.S.; Crisler, M.; Dahl, C.E.; Fustin, D.; Grace, E.; Hall, J.; Hu, M.; Levine, I.; Lippincott, W. H.; Moan, T.; Nania, T.; Ramberg, E.; Robinson, A.E.; Sonnenschein, A.; Szydagis, M.; Vázquez-Jáuregui, E. (September 2012). "First dark matter search results from a 4-kg CF3I bubble chamber operated in a deep underground site". Physical Review D. 86 (5): 052001–052009. arXiv:1204.3094. Bibcode:2012PhRvD..86e2001B. doi:10.1103/PhysRevD.86.052001. S2CID 28797578. FERMILAB-PUB-12-098-AD-AE-CD-E-PPD.
  38. Smith, Nigel J.T. (2013-09-08). "Infrastructure Development for underground labs—SNOLAB experience" (PDF). 13th International Conference on Topics in Astroparticle and Underground Physics. Asilomar, California.
  39. "The old COUPP detector using bubble chamber technology to search for dark matter. It is not running right now because they have a bigger detector to assemble and play with!" (2013-01-18)
  40. Smith, Nigel (17 June 2015). Advanced Instrumentation Techniques in SNOLAB (PDF). 2015 Canadian Association of Physicists Congress.
  41. Sinclair, David (12 September 2013). The SNOLAB Science Programme. 13th International Conference on Topics in Astroparticle and Underground Physics. Asilomar, California. Retrieved 2014-11-21.
  42. Pocar, Andrea (8 September 2014). Searching for neutrino-less double beta decay with EXO-200 and nEXO (PDF). Neutrino Oscillation Workshop. Otranto. Retrieved 2015-01-10.
  43. Yang, Liang (8 July 2016). Status and Prospects for the EXO-200 and nEXO Experiments (PDF). XXVII International Conference on Neutrino Physics and Astrophysics. London. Video available at Neutrino Conference 2016 - Friday (part 1) on YouTube.
  44. Vázquez-Jáuregui, Eric (2017-07-25). PICO-500L: Simulations for a 500L Bubble Chamber for Dark Matter Search (PDF). TAUP2017.
  45. Noble, T. (2009-02-18). "SNOLAB: AstroParticle-Physics Research in Canada" (PDF). p. 4.
  46. Vázquez-Jáuregui, Eric (2014-01-30). Facility and experiment developments at SNOLAB (PDF). Fourth International Workshop for the Design of the ANDES Underground Laboratory.

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