SNO+ Mark Chen Queen’s University

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 SNO+ Collaboration a subset of the SNO collaboration will continue with SNO+

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 Outline

SNO plus liquid scintillator plus double beta isotopes: SNO++ add  isotopes to liquid scintillator –dissolved Xe gas (2%) –organometallic chemical loading (Nd, Se, Te) –dispersion of nanoparticles (Nd 2 O 3, TeO 2 ) enormous quantities (high statistics) and low backgrounds help compensate for the poor energy resolution of liquid scintillator possibly source in–source out capability Double Beta Decay: SNO++

Candidate Selection

150 Nd 3.37 MeV endpoint (9.7 ± 0.7 ± 1.0) × yr 2  half-life measured by NEMO-III isotopic abundance 5.6% 1% natural Nd-loaded liquid scintillator in SNO++ has 560 kg of 150 Nd compared to 37 g in NEMO-III cost: $1/g for metallic Nd; cheaper as Nd salt…on the web NdCl 3 sold in lot sizes of 100 kg, 1 ton, 10 tons table from F. Avignone Neutrino 2004

2  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

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

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

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 Enriched Nd Scintillator

external 241 Am  Compton edge 137 Cs 207 Bi conversion electrons Nd LS Works!

SNO++ Double Beta Sensitivity insensitive to internal radon backgrounds insensitive to external backgrounds (2.6 MeV gamma) internal Th is the main concern –and 2 background, of course homogeneous, well defined background model for m = 50 meV, 0 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 2 double beta decay backgrounds –gives a 5  exclusion of 50 meV after one year …shows the advantage of huge amounts of isotope, thus high statistics

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)

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

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

SNO+ Spectral Distortion oscillated rate: 180 events (per proton-years) unoscillated expectation: 320 events 1 kiloton CH 2 scintillator: 0.86 × protons T. Araki et al., hep-ex/ (2004)

Bruce Baselines: 240 and 340 km Pickering Darlington

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  = 0.86 g/cm 3 –SNO+ light output (photoelectrons/MeV) will be approximately 4× that of KamLAND

SNO+ Monte Carlo light yield simulations KamLAND scintillator in SNO+ 629 ± 25 pe/MeV above no acrylic711 ± 27 pe/MeV KamLAND scintillator and 50 mg/L bisMSB 826 ± 24 pe/MeV above no acrylic 878 ± 29 pe/MeV KamLAND (20% PC in dodecane, 1.52 g/L PPO) ~300 pe/MeV for 22% photocathode coverage SNO+ has 54% PMT coverage; acrylic vessel only diminishes light ouput by ~10%

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

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

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. 210 Pb) –at Queen’s alumina: 98-99% extraction efficiency distillation: >99.9% extraction efficiency, single pass

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

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

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)

Schedule 01/2007 to 04/2007temporary construction during SNO decommissioning (inspect AV, radon-free cover gas) 05/2007 to 10/2007design of AV conversion 05/2007 to 12/2007engineering of scintillator fluid process 01/2008 to 11/2008AV conversion construction 03/2008 to 05/2008scintillator procurement logistics and contracts 05/2008 to 04/2009scintillator purification construction 05/2009 tostart SNO+ filling

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 SNOLAB infrastructure requirements

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

Cash Flow Table SNO+Nd initiative 2007/08$2.0M$0.4M 2008/09$9.3M$1.7M + $0.8M