status and prospects of sno+

Status and Prospects of SNO+

José Maneira, LIP-Lisboaon behalf of the SNO+ collaboration

NOW2010, Conca SpecchiullaSeptember 5, 2010

J. Maneira (LIP) / SNO+ / NOW2010/ Conca Specchiulla / September 5, 2010

2

Outline

Introduction Detector developments

Physics goals


3

Sudbury Neutrino Observatory SNO

• Deepest large underground detector

• What advantages in re-using it with scintillator after the heavy water?


6

Expansion of the underground area and new surface facilities for SNO+ and several other experiments in Dark Matter and Neutrino Physics


7

SNO+ 1000 t of D

2O replaced

by liquid scintillator• Neodymium-loaded at 0.1%

• 780 kg of natural Nd

9000 PMTs• 3.5 % resolution at � � Nd

endpoint (3.37 MeV)

Water shield• 1700 + 5300 tons UPW

New rope system to hold down the 6 m radius acrylic vessel


8

SNO+ 1000 t of D

2O replaced

by liquid scintillator• Neodymium-loaded at 0.1%

• 780 kg of natural Nd

9000 PMTs• 3.5 % resolution at � � Nd

endpoint (3.37 MeV)

Water shield• 1700 + 5300 tons UPW

New rope system to hold down the 6 m radius acrylic vessel


9

Comparative advantages There's already Borexino and KamLAND, why

another liquid scintillator detector? Size

• 780 tons of scintillator, compared to 300 tons (Borexino)

Depth• SNO+ is at 6080 mwe, while Borexino is at 3500 mwe and

KamLAND at 2700 mwe. o Low cosmogenic backgrounds.o Best location for a precision measurement of the pep solar neutrino fluxo … and CNO discovery

Resolution: • SNO+ has ~9000 PMTs, compared to ~2200

• with Nd loading: 5% at 1 MeV, 3.5 % at 3.4 MeV


10

Many developments needed Find and characterize a suitable scintillator Design and install purification plants Re-engineer Acrylic Vessel support for buoyancy force Maintenance of SNO cavity Re-cleaning of acrylic vessel Re-design calibration systems PMT repairs Maintenance and upgrade of electronics and trigger Software developments


11

Scintillator development “New” scintillator developed: LAB

• Compatible with acrylic, undiluted

• High light yield

• Optical transparency

• Low scattering

• Fast decay, different for alpha/beta

• High flash point, low toxicity

Metal-loading also developed• Organometallic Nd compound

• Neodymium has poor transparency

• Considering a low loading of 0.1 %

• ~44 kg of Nd-150 (with natural)


12

Purification systems Several fluids to handle

• Light water• Bulk scintillator• Fluor (PPO) solution• Neodymium-loaded compound

Scintillator plant• Distillation• Water extraction• Gas removal• Filtration and ultra-filtration• R&d on metal scavenger columns

Goals• Scintillator purity of 1x10-17 g/g U/Th

o Reached by Borexinoo C-14,Kr-85 not a problem because of low energy, C-11 not a

problem because of depth

• Nd-compound purity of < 1x10-14 g/g U/Tho Need factor of 106 reduction

Test plants at SNOLAB

Water extraction

Distillation

Status• designed• pit excavation

underway


13

Scintillator tests in SNO “Bucket” source

• 3 types of scintillator

• with/without neutron source

• Deployed Fall 2008, while AV was full with water

Results• Light yields

• Resolution 3.5% at 3.4 MeV

• Alpha quenching factors

• Birks parameters


14

AV support

Light Water

SNO: Heavy water density 1.1SNO+: LAB scintillator density 0.86


15

Acrylic vessel hold-down New rope system

• Finite element analysis of AV stress and buckling done

• Material constraintso Strength (reduced thickness)o Radiopurity (external background) o Tensylon chosen

• Will replace also old support ropes


16

New SNO+ simulation Based on GEANT4

• Adapted from GLG4sim and Braidwood package

• In development now, being validated against SNOMAN and “bucket” source data


17

Other HW upgrades Electronics

• Replace some boards

• Improve data rate capacity

• Re-map PMTs, matching dead ones with dead channels

• Improve stock of spares

Calibrations• Make existing HW scintillator

compatibleo New radon-sealed glove-boxo Replace umbilicals

• Make new, lower-energy, sources

• Design new systems to calibrate from outside the AV

Detector cavity• Re-seal floor lining


18

Physics program Neutrinoless Double-Beta Decay Solar Neutrinos Reactor and Geo-neutrinos Neutrinos from Supernovae


19

Double-beta decay With scintillators?

• large mass, low background

• poor energy resolution

Separation from 2-nu decay • fit spectral shape at 2-nu

endpoint

Separation from backgrounds• choose high Q-value isotope

o above 2.6 MeV, natural radioactivity spectrum is a continuum

• low background detector

isotopes with high Q-value


20

Double-beta decay at SNO+ Neodymium successfully loaded in LAB

• Optics properties suffer though, aiming for 0.1% loadingo Attenuation measured, light yield expected at ~400 p.e./MeV

• with Natural Neodymium, that's about 44 kg of Nd-150

Expected signal• <m

ν>= 270 meV

• 1 kT-year exposure

• 214Bi and 208Tl at Borexino levels

well-known “background” from8B solar neutrinos


21

baseline half-life sensitivity

150Nd (43.7 kg)

using IBM-2 matrix element (2.5)


22

baseline mass sensitivity

150Nd (43.7 kg)


23

Solar neutrinos Neutrino sources

• Super-K and SNO measured 8B

• Borexino measured 7Be

• Subtracting 8B and 7Be, pp comes from Ga experiments

• Still missing pep and CNO!

Oscillations at low energy• New Physics models predict different

survival probabilities in vacuum-matter transition region

• Measurement reaction is ESo Need total flux from SSM

• (after pp), pep is the best-known SSM flux

o 1.1 % (2.8% from metallicity)o 7Be: 5.8% (10% from metallicity)


24

New questions about the Sun Metal abundances and helioseismology

• Improved 3-D models give a 30% lower metallicity (X)

• But then the sound speeds disagree with helioseismology!

• What if the Sun's metallicity is not homogenous?o According to Haxton and Serenelli, the core could have a higher X than the

convective zone

Can neutrinos (and SNO+) help?• CNO neutrinos depend linearly on X

• Temperature dependence same as 8B

••• A measurement of CNO neutrinos at

SNO+ can help pin down the Sun's metallicity

Haxton, Serenelli, astro-ph/0902.0036v1


25

Why SNO+ for pep? Cosmogenic backgrounds

• Carbon-11 decays cover pep and CNO energy windowo Seen by Borexino and KamLAND Borexino Collaboration, Phys.

Rev. Lett. 101, 091302 (2008)

Franco, Galbiati et al., Phys.Rev.C71:055805,2005

pep edge

C-11 counts within 0.8-1.3 MeV

Depth matters• Carbon-11produced by cosmic muons hitting organic molecules

• SNO+ (6080 mwe) 100 times better than Borexino (3500 mwe), 600 times better than KamLAND (2700 mwe)

o Borexino developing C-11 cut, SNO+ will not need it


26

Reactor Neutrino Physics

• Flux 5x smaller than at Kamioka, but...

• Sensitivity to 2nd, 3rd, 4th oscillation minima

SNO+

KamLAND


27

Geo-neutrinos Production

• Anti-neutrinos from U-238, Th-232 and K-40 on Earth

• Contributions from crust and mantle depend on locationo 20% from mantle at SNO+o Check models of Earth heat production

Detection• Around 20 events per year (efficiencies included)

• Smaller background from reactors than KamLAND


28

Supernovae

SNEWS• Supernova Early Warning System

• Detection coincidence gives alert to astronomical community

• SNO was in until Nov. 2006, SNO+ will join

SNO+ SN signal from 10 kpc• About 600 events (1/10 of SuperK)

• ½ Charged Current, ½ Neutral Current


29

Timeline 2010

• Cavity work

• Cleaning

• PMT repairs

2011• Install hold-down rope “basket”

• Install purification systems

• Install new calibration hardware

• Electronics upgrades ready

• Begin water fill

2012• Summer: Detector filled with scintillator

• start data-taking!


30

Lisbon, June 2010Collaboration Meeting

The CollaborationUniversity of AlbertaA. Bialek, P. Gorel, A. Hallin, M. Hedayatipoor, C. Krauss, L. SibleyArmstrong Atlantic State UniversityJ. SecrestBlack Hills State UniversityK. KeeterBrookhaven National laboratoryR. Hahn, M. Yeh, Y. WilliamsonTechnical University of DresdenV. Lozza, B. von Krosigk, P. Schrock, K. ZuberLaurentian UniversityO. Chkvorets, E.D. Hallman, S. Korte, C. Kraus, M. Schumaker, C. VirtueUniversity of LeedsS. Bradbury, J. RoseLIP Lisboa + CoimbraS. Andringa, N. Barros, J. Carvalho, L. Gurriana, A. Maio, J. ManeiraUniversity of LiverpoolN. McCauleyUniversity of North Carolina at Chapel HillM. Howe, J. WilkersonOxford UniversityS. Biller, P. Jones, N. Jelley, A. ReicholdUniversity of PennsylvaniaE. Beier, R. Bonventre, W.J. Heintzelman, J. Klein, P. Keener, R. Knapik, A. Mastbaum, G. Orebi-Gann, T. Shokair, R. Van BergQueen Mary, University of LondonJ. Wilson-HawkeQueen's UniversityS. Asahi, M. Boulay, M. Chen*, N. Fatemighomi, P.J. Harvey, X. Liu, A. McDonald, A. Noble, H. O'Keefe, E. O'Sullivan, P. Skensved, A. WrightSNOLABB. Cleveland, F. Duncan, R. Ford, C.J. Jillings, I. Lawson, E. Vásquez-JaureguiUniversity of SussexE. Falk-Harris, S. Fernandes, J. Hartnell, S. PeetersUniversity of WashingtonS. Enomoto, J. Kaspar, J. Nance, D.Scislowski, N. Tolich, H. Wan Chan Tseung

status and prospects of sno+

Documents