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SNO+

SNO+. Mark Chen Queen’s University. SNO+ Collaboration. Queen’s M. Chen, M. Boulay, X. Dai, E. Guillian, A. Hallin, P. Harvey, C. Hearns, C. Kraus, C. Lan, A. McDonald, V. Novikov, S. Quirk, P. Skensved, A. Wright, U. Bissbort Carleton K. Graham Laurentian D. Hallman, C. Virtue

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SNO+

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  1. SNO+ Mark Chen Queen’s University

  2. SNO+ Collaboration Queen’s M. Chen, M. Boulay, X. Dai, E. Guillian, A. Hallin, P. Harvey, C. Hearns, C. Kraus, C. Lan, A. McDonald, V. Novikov, S. Quirk, P. Skensved, A. Wright, U. Bissbort Carleton K. Graham Laurentian D. Hallman, C. Virtue Trent J. Jury SNOLAB B. Cleveland, F. Duncan, R. Ford, I. Lawson Brookhaven National Lab D. Hahn, M. Yeh, A. Garnov, Idaho State University K. Keeter University of Texas at Austin J. Klein University of Pennsylvania G. Beier (for Nd double beta decay) LIP Lisbon J. Maneira, N. Barros, S. Andringa Technical University Munich L. Oberauer, F. v. Feilitzsch (for Nd double beta decay) Sussex K. Zuber • potential collaborators from outside SNO (Italy, Russia) have indicated some interest a subset of the SNO collaboration will continue with SNO+

  3. Outline • SNO+ physics overview • double beta decay • pep solar neutrinos • geo-neutrinos • reactor neutrino oscillation confirmation • supernova neutrino detection • technical progress • cost and schedule • collaboration resources

  4. Double Beta Decay: SNO++ • SNO plus liquid scintillator plus double beta isotopes: SNO++ • add bb isotopes to liquid scintillator • dissolved Xe gas (2%) • organometallic chemical loading (Nd, Se, Te) • dispersion of nanoparticles (Nd2O3, TeO2) • enormous quantities (high statistics) and low backgrounds help compensate for the poor energy resolution of liquid scintillator • possibly source in–source out capability

  5. Candidate Selection

  6. table from F. Avignone Neutrino 2004 150Nd • 3.37 MeV endpoint • (9.7 ± 0.7 ± 1.0) × 1018 yr 2nbb half-life measured by NEMO-III • isotopic abundance 5.6% 1% natural Nd-loaded liquid scintillator in SNO++ has 560 kg of 150Nd compared to 37 g in NEMO-III • cost: $1/g for metallic Nd; cheaper as Nd salt…on the web NdCl3 sold in lot sizes of 100 kg, 1 ton, 10 tons

  7. 2nbb Background • good energy resolution needed • but whopping statistics helps compensate for poor resolution and… turns this into an endpoint shape distortion measure rather than a peak search

  8. Test <mn> = 0.150 eV Klapdor-Kleingrothaus et al., Phys. Lett. B 586, 198, (2004) 0n: 1000 events per year with 1% natural Nd-loaded liquid scintillator in SNO++ simulation: one year of data maximum likelihood statistical test of the shape to extract 0n and 2n components…~240 units of Dc2 significance after only 1 year!

  9. made by Yeh, Garnov, Hahn at BNL Nd-carboxylate in Pseudocumene window with >6 m light attenuation length {

  10. Enriched Nd Scintillator • at 1% loading (natural Nd), there is too much light absorption by Nd • 47±6 pe/MeV (from Monte Carlo) • at 0.1% loading (isotopically enriched to 56%) our Monte Carlo predicts • 400±21 pe/MeV (from Monte Carlo) • good enough to do the experiment

  11. Nd LS Works! external 241Am a 207Bi conversion electrons Compton edge 137Cs

  12. SNO++ Double Beta Sensitivity • insensitive to internal radon backgrounds • insensitive to external backgrounds (2.6 MeV gamma) • internal Th is the main concern • and 2n background, of course • homogeneous, well defined background model • for mn = 50 meV, 0n signal is ~60 events/yr in the upper-half of the peak, with S:B about 1:1 • based upon KamLAND Th levels in scintillator and known 2n double beta decay backgrounds • gives a 5s exclusion of 50 meV after one year • …shows the advantage of huge amounts of isotope, thus high statistics

  13. Nd-150 Consortium • SuperNEMO and SNO+, MOON and DCBA have joined together to try to maintain an existing French AVLIS facility that is capable of making 100’s of kg of enriched Nd • a facility that enriched 204 kg of U (to 2.5% from 0.7%) in several hundred hours (i.e. about 1 week)

  14. 2000–2003 Program : Menphis facility Evaporator Dye laser chain Yag laser Copper vapor laser Design : 2001 Building : 2002 1st test : early 2003 1st full scale exp. : june 2003

  15. Reactor Antineutrinos • SNO+ can confirm reactor neutrino oscillations • an interesting test! • move KamLAND’s spectral distortion to higher energies by going to a slightly longer baseline

  16. SNO+ Spectral Distortion T. Araki et al., hep-ex/0406035 (2004) oscillated rate: 180 events (per 1032 proton-years) unoscillated expectation: 320 events 1 kiloton CH2 scintillator: 0.86 × 1032 protons

  17. Baselines: 240 and 340 km Bruce Pickering Darlington

  18. SNO+ Technical Progress • liquid scintillator identified • linear alkylbenzene • compatible with acrylic, undiluted • high light yield • pure (light attenuation length in excess of 20 m at 420 nm) • low cost • high flash point • low toxicity • smallest scattering of all scintillating solvents investigated • density r = 0.86 g/cm3 • SNO+ light output (photoelectrons/MeV) will be approximately 4× that of KamLAND

  19. SNO+ Monte Carlo • light yield simulations SNO+ has 54% PMT coverage; acrylic vessel only diminishes light ouput by ~10%

  20. LAB Scintillator Optimization “safe” scintillators LAB has 75% greater light yield than KamLAND scintillator

  21. Light Attenuation Length Petresa LAB as received attenuation length exceeds 10 m preliminary measurement ~10 m

  22. Scintillator Purification • optical • at BNL and at Queen’s • improves light attenuation length, removing impurities that absorb light, especially at lower wavelengths • alumina column and vacuum distillation both work • radioactivity (e.g. 210Pb) • at Queen’s • alumina: 98-99% extraction efficiency • distillation: >99.9% extraction efficiency, single pass

  23. Scintillator-Acrylic Compatibility • ASTM D543 “Standard Practices for Evaluating the Resistance of Plastics to Chemical Reagents”

  24. Acrylic Vessel Hold-down • “rope net” being designed to hold down 15% density difference • alternative: machine reverse rope grooves in existing belly plates SNO SNO+

  25. Cost ($ CAD) incremental cost to convert SNO to SNO+ liquid scintillator $2.0M AV conversion $1.5M scintillator purification $7.0M (includes fluid handling logistics, safety) cover gas, glove box $0.3M DAQ upgrade $0.5M total: $11.3M incremental cost for 500 kg enriched Nd (rough estimate) feasibility study $0.4M (international total: 1-3 M€) running facility $1.5M purchase Nd $1.0M (the intent is to sell back depleted Nd)

  26. Schedule

  27. SNOLAB infrastructure requirements • Integration with SNO decommissioning • Need approval for LAB scintillator from Inco • Distillation of LAB is being planned u/g and will require 100kW-1MW of power and cooling

  28. SNOLAB R&D needs • Support for investigations into novel purification techniques (nanofiltration) • Radon-reduced (radon-free) air

  29. Cash Flow Table

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