SNO+

Rope basket used to anchor the acrylic vessel.

SNO+ is an underground physics experiment under construction (as of Nov 2015) that makes use of the equipment already installed underground for the former Sudbury Neutrino Observatory (SNO) experiment at SNOLAB. The main goals of the project are a search for neutrinoless double beta decay, with secondary measurements of proton–electron–proton (pep) solar neutrinos, geoneutrinos from radioactive decays in the Earth, and reactor neutrinos. It will also be possible to observe supernovae neutrinos if a supernova should occur in our galaxy.

Testing and construction

Testing (filled with water) is expected to begin early 2016, with full operation with liquid a few months after that, and the Te-loaded phase in 2017.[1] In order to reach these goals, linear alkyl benzene will be used as a liquid scintillator and target material.[2]

A neutrino interaction with this liquid produces several times more light than an interaction in a water Cherenkov experiment such as the original SNO experiment or Super-Kamiokande. The energy threshold for the detection of neutrinos therefore can be lower, and proton–electron–proton solar neutrinos (with an energy of 1.44 MeV) can be observed. In addition, a liquid scintillator experiment can detect anti-neutrinos like those created in nuclear fission reactors and the decay of thorium and uranium in the earth.

A mass of many tons of double beta decaying material (Tellurium-130) will then be added to the experiment.[3] This will make SNO+ the largest experiment to study neutrinoless double beta decay.

Earlier proposals placed more emphasis on neutrino observations. The current emphasis on neutrinoless double beta decay is because the interior of the acrylic vessel has been significantly contaminated by radioactive daughter products of the radon gas that is common in the mine air. Depending on the (currently unknown) rate at which these leach into the scintillator, compared with the rate at which they are removed by the filtration system, they may interfere with low-energy neutrino measurements.[3]:21 The neutrinoless double beta decay observations are not affected by this.

The project received funding for initial construction from NSERC in April 2007, and as of early 2013, the cavity had been refurbished and re-sealed to the new cleanliness standards, which are (due to the experiment's greater sensitivity) more stringent than for the original SNO.

The main civil engineering challenge is that the current SNO vessel is supported by a series of ropes, to prevent the weight of the heavy water inside from sinking it in the surrounding normal water. The proposed liquid scintillator (linear alkyl benzene) is lighter than water, and must be held down instead, but still without blocking the view of its interior. The existing support rope attachment points, cast into the acrylic sphere's equator, are not suitable for upside-down use.

Computing

The collaboration is investigating the use of grid resources to deliver the computing power needed by the experiment. This is after the success of the LHC Computing Grid (wLCG) used by the LHC experiments. The SNO+ VO has been using resources provided by GridPP.[4]

References

  1. ↑ SNO+ Collaboration; :; Andringa, S.; Arushanova, E.; Asahi, S.; Askins, M.; Auty, D. J.; Back, A. R.; Barnard, Z.; Barros, N.; Beier, E. W.; Bialek, A.; Biller, S. D.; Blucher, E.; Bonventre, R.; Braid, D.; Caden, E.; Callaghan, E.; Caravaca, J.; Carvalho, J.; Cavalli, L.; Chauhan, D.; Chen, M.; Chkvorets, O.; Clark, K.; Cleveland, B.; Coulter, I. T.; Cressy, D.; Dai, X.; et al. (2015-11-13). "Current Status and Future Prospects of the SNO+ Experiment". arXiv:1508.05759 [physics.ins-det].
  2. ↑ Lasserre, T.; Fechner, M.; Mention, G.; Reboulleau, R.; Cribier, M.; Letourneau, A.; Lhuillier, D. (2010). "SNIF: A Futuristic Neutrino Probe for Undeclared Nuclear Fission Reactors". arXiv:1011.3850 [nucl-ex].
  3. 1 2 Kaspar, Jarek; Biller, Steve (10 September 2013). SNO+ with Tellurium. 13th International Conference on Topics in Astroparticle and Underground Physics. Asilomar, California. Retrieved 2015-08-18.
  4. ↑ "Grid Computing". SNO+. Retrieved 2014-08-05.

Further reading

External links

This article is issued from Wikipedia - version of the Thursday, December 03, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.