SNO+

Mark ChenQueen’s University

Queen’sM. 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

LaurentianD. Hallman, C. Virtue

TrentJ. Jury

SNOLABB. Cleveland, F. Duncan, R. Ford, I. Lawson

Brookhaven National LabD. Hahn, M. Yeh, A. Garnov,

Idaho State UniversityK. Keeter

University of Texas at AustinJ. Klein

University of PennsylvaniaG. Beier (for Nd double beta decay)

LIP LisbonJ. Maneira, N. Barros, S. Andringa

Technical University MunichL. Oberauer, F. v. Feilitzsch (for Nd double beta decay)

SussexK. 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 (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

Double Beta Decay: SNO++

Candidate Selection

150Nd

• 3.37 MeV endpoint• (9.7 ± 0.7 ± 1.0) × 1018 yr

2half-lifemeasured 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

table from F. Avignone Neutrino 2004

2 Background

• good energy resolution needed

• but whopping statisticshelps compensate for poorresolution and…

turns this into an endpointshape distortion measurerather than a peak search

0: 1000 events peryear with 1% naturalNd-loaded liquidscintillator in SNO++

Test <m> = 0.150 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 Pseudocumenemade 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 241Am

Compton edge 137Cs 207Bi conversionelectrons

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 : 2001Building : 20021st test : early 20031st full scale exp. : june 2003

EvaporatorDye laser chainYag laserCopper 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 1032 proton-years)unoscillated expectation: 320 events

1 kiloton CH2 scintillator: 0.86 × 1032 protons

T. Araki et al., hep-ex/0406035 (2004)

BruceBruce

Baselines: 240 and 340 km

PickeringDarlington

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/cm3

– 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 acrylic 711 ± 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 LengthPetresa LABas 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. 210Pb)

– 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

SNO SNO+

Cost ($ CAD)

incremental cost to convert SNO to SNO+liquid scintillator $2.0MAV conversion $1.5Mscintillator purification $7.0M (includes fluid handling logistics,

safety)cover gas, glove box $0.3MDAQ upgrade $0.5Mtotal: $11.3M

incremental cost for 500 kg enriched Nd (rough estimate)feasibility study $0.4M (international total: 1-3 M€)running facility $1.5Mpurchase Nd $1.0M (the intent is to sell back depleted Nd)

Schedule01/2007 to 04/2007 temporary construction during SNO decommissioning

(inspect AV, radon-free cover gas)

05/2007 to 10/2007 design of AV conversion

05/2007 to 12/2007 engineering of scintillator fluid process

01/2008 to 11/2008 AV conversion construction

03/2008 to 05/2008 scintillator procurement logistics and contracts

05/2008 to 04/2009 scintillator purification construction

05/2009 to start 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 initiative2007/08 $2.0M $0.4M2008/09 $9.3M $1.7M + $0.8M