SNO+ ArtFest, May 2014, Kingston Dr. Christine Kraus...

SNO+ ARTFEST, MAY 2014, KINGSTON

DR. CHRISTINE KRAUS, LAURENTIAN UNIVERSITY

SNO+ IS LOCATED AT SNOLAB

300 km

2 km or

6000 m.w.e.

CanadaOntarioSudburyCreighton mine

use existing SNO cavity

2Artfest 2014, Christine Kraus, Laurentian University

SNO DETECTOR (INHERITED)

1000 tonnes D2O

12 m acrylic vessel

1700 t H2O (inner)

18 m PSUP

5300 t H2O (outer)~9500 PMTs54% coverage

DCR = Deck Clean Room

Acrylic vessel AV,filled with 1000 tonnes of heavy water: 1999-2006 data takingin 3 phases (different n detection methods)

sunset in Sudbury

3Artfest May 2014, Christine Kraus, Laurentian University

780 tonnes liquid

org. scintillator

Hold-down

ropenet

LIQUID SCINTILLATOR

Detector to be filled with 780 tonnes of organic liquid scintillator (LS)

More light yield than Čerenkov , around 400 p.e./MeV, enabling lower energy threshold

Linear alkylbenzene (LAB)

High light yield

Long attenuation length

Safe: high flash point and low toxicity

More affordable than other scintillators

Add wavelength shifter

Initial plan: 2g/L PPO fluor4

SNO+ liquid scintillator ! Detector to be filled with 780 tonnes of organic liquid

scintillator

! ~100 times more light yield than Čerenkov ~ lower energy threshold

! Linear alkylebenzene (LAB) - High light yield

- Long attenuation length

- Safe: high flash point and low toxicity

- Cheaper than other scintillators

! 2g/L PPO fluor shifts the wavelength of the emitted light into detectable region

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Artfest May 2014, Christine Kraus, Laurentian University

SNO+ PHYSICS GOALS

Neutrinoless double beta decay

– scintillator loaded with 130Te

(0.3% loading – 800 kg of 130Te)

Geo- and Reactor neutrinos

Supernova neutrinos

Solar neutrinos (pep, CNO, low 8B)

Nucleon decay, sterile neutrinos

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Multi-purposedetector


NEUTRINOLESS DOUBLE BETA DECAY

Loading the scintillator with isotope

Can compare with and without source in the same detector

Can in principle investigate several isotopes with the same detector

What is the best isotope?

Originally decided on 150Nd due to it’s high Q-value and phase

space (away from many backgrounds), were hoping for

possibility to enrich

In principle SNO+ can measure different isotopes (source in/out)

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DOUBLE BETA ISOTOPES

35 known isotopesDecay

candidate

Q-

value

(MeV)

% natural

abundance

48Ca48Ti 4.271 0.187

76Ge76Se 2.040 7.8

82Ca82Kr 2.995 9.2

96Zr96Mo 3.350 2.8

100Mo100Ru 3.034 9.6

110Pd110Cd 2.013 11.8

116Cd116Sn 2.802 7.5

124Sn124Te 2.228 5.64

130Te130Xe 2.533 34.1

136Xe136Ba 2.479 8.9

150Nd150Sm 3.367 5.67


SNO+ WITH TELLURIUM

Fall 2011: Biller and Chen initiate new investigation by subgroup of collaboration

Early 2012: new loading techniques for Te in liquid scintillator was developed by Yeh at al.

Detailed studies of purification, optics properties, backgrounds by the collaboration followed

Also independent review and verification studies were completed

March 2013 – collaboration decides to focus on 130Te as the double beta isotope to pursue

8


ADVANTAGES OF TELLURIUM

34% natural abundance

2νββ rate is low

no inherent optical absorption lines

High values of loading feasible (default 0.3%)

Internal U/Th background can be actively

suppressed by identifying 214Bi-214Po alphas

9


LOADING SCINTILLATOR (BNL)

Conventional

Loading

Method

Carboxylate

Organometallic

Complex

New loading technique (BNL):

Dissolve telluric acid in water and add a few

percent of this mixture to LAB using a

surfactant. Clear and stable has been

demonstrated for more than 1 year.

ICP-MS determined U/Th content of telluric

acid to be 2-3 times 1011 g/g

U/Th purification factors of >400 in a single

pass have been achieved. 10


PERCENT LOADING OF TELLURIUM

0.3%, 0.5%, 1%, 3%, 5% (from left to right)

SNO+ EXPECTED SPECTRUM

12

Expected

sensitivity

is below

100 meV

for 0.3%

loading

(800 kg)

★ 2 years lifetime and fiducial volume cut at 3.5 m (20%)

★ > 99.99% efficient 214 Bi tag, 97% efficient internal 208Tl tag

★ Factor 50 reduction 212BiPo and negligible cosmogenic isotopes

★ m0ν2β= 200 meV assumed for this plot


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SNO+ PROJECTED SENSITIVITY


SOLAR NEUTRINOS: PEP

14

★ pep solar neutrino component is favorable:

- single energy (1.442 MeV) and well predicted flux (1.1%)

★ Probes the vacuum-matter transition region

★ Can be measured during pure liquid scintillator phase

Probability vs. Energy Simulated spectrum

8Bpep

CNO


CONSTRUCTION STATUS

Hold-down system completed, Hold-up ropes exchanged

Water fill of cavity started

Cleaning the inner surface of AV completed

Scintillator purification plant coming together

STF completed, testing upcoming

PMT repairs ongoing

Calibration hardware starting to be installed

Detector electronics commissioning – air filled running

New covergas system installed and commissioned

Fiber system and camera system partially installed

15


HOLD-DOWN SYSTEM

Feb. 2011: Install tarp –

Cleanliness protection May 2011:

drill 80 + 15 holes

Jan 2012

Install rope net

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Pre-tensioning – Jan 2013

May 2013: Set positions for

AV and hold-down sys.Jan 2012:

Replace hold-up

ropes

Sep 2013

Shorten hold-up

ropes

Completed !


JANUARY 2012 AND SEPTEMBER 2013

Jan 2012:

Replace hold-up

ropes

Sep 2013

Shorten hold-up

ropes

AV CLEANING COMPLETE !

18

Suspended

platform Carousel and access

Inside AV, looking

down Outside AV

Cleaning ladder

Cleaning entire

Inner surface:

Jan-Mar 2013


CAVITY WITH WATER

19


SCINTILLATOR PLANT

20

All vessels, kettles,

etc. underground

and installation

ongoing

He-leak checking

of components

mostly completed

Large column

Slung, arriving UG

2h fire walls

Piping to do

Fire protection and

suppression to be

completed


DETECTOR

21

Upgrade electronics, bring everything online

DAQ tests, LED system tests, air-filled running

Repair PMTs ~300 so far

Install

UI and acrylic pipes

May 2013

Getting ready for running with water - 2013


SNO+ DARK RUNNING – DECEMBER 2013

AND FEBRUARY 2014

With about 200 PMTs under water, turned on complete detector

with HV and ran for 8 days

Training detector experts and commissioning system components

Weekend and night shifts operated from surface

Took full set of PMT calibration data: electronics and timing

Data to test PMT calibration code

Testing new monitoring tools


WATER LEVEL ABOVE PMTS


WATER LINE – DECEMBER 2013

4 (out of 19) crates with HV, rates for PMTs

Under water higher (as expected)


USING INSTALLED FIBERS – FEBRUARY 2014

Water level 12 ft from cavity floor

Timing calibration data

Testing system

Stress test for DAQ

Optical calibration without need to Insert source into the detector, Minimize contamination risk.


FIBER DATA

11.2 million events total for timing calibrationArtfest May 2014, Christine Kraus, Laurentian University

MUON


NEW COVER GAS SYSTEM WAS

INSTALLED AND TESTED



Cover Gas Pictures

SUMMARY AND OUTLOOK

Water fill has begun, plan to be filled by the end of the year

Remaining PSUP installations (fibers, cameras, etc.)

Water phase data taking (2014)

Fill with scintillator – start background studies

Introduction of isotope in stages: 2015

Exciting times ahead

30


31

Oxford UniversitySussex University

Liverpool UniversityQueen Mary UniversityLancaster University

University of PennsylvaniaUniversity of Chicago

University of Washington Armstrong Atlantic UniversityUniversity of North Carolina

UC Berkeley and LBNLUC Davis

Queen’s UniversityLaurentian UniversityUniversity of Alberta

TRIUMF

SNOLAB

LIP Lisboa and

CoimbraTechnical University

of Dresden

YESTERDAY’S COLLABORATION PHOTO

August 2013 Collaboration meeting

BACKUP SLIDES …

OPTICAL PROPERTIES

34

Absorption vs. wavelength

Te does not have absorption lines

Optically clear

Wavelength shifter options under

investigation to further improve

Triggers vs. Total Charge

Average light level 200-300 hits/MeV


BACKGROUNDS

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214Po – 164.3μs

Q-value: 3.27 MeV

212Po – 3x10-7s

Q-value: 2.25 MeV

target level ~2.5x10-15gU/gcocktail

~3x10-16gTh/gcocktail

★ Several α and βemissions

★ Direct backgrounds

★ 212Bi-212Po w coinc. 98% rejection

★ 214Bi-214Po w coinc. 99.8% rejection

★ 214Bi-214Po iw coinc. 98% rejection

★ 212Bi-208Tl coinc. 97% rejection

★ Continue to investigate, improve

External backgrounds from

AV, rope net, PMTs, water shield Attenuated by fiducial

volume, 50%time likelihood cut


SOLAR NEUTRINOS: CNO

36


SOLAR NEUTRINOS Background studies in pure scintillator will be available years

before to determine strategy to achieve background goals

Radon daughters have accumulated on the surface of the AV

over the last few years in a significant way. If these leach into the

scintillator, the purification system has the capability to remove

them.

However, depending on the actual leach rate, that removal

might be inefficient and the 210Bi levels in the scintillator too high

for a pep/CNO solar neutrino measurement without further mitigation.

Mitigation should include enhancing online scintillator purification,

draining the detector and sanding the AV surface to remove

radon daughters, or deploying a bag

Double beta decay and low energy 8B solar neutrino

measurements are not effected by these backgrounds. 37


GEO- AND REACTOR NEUTRINOS

38


NUCLEON DECAY AND SN NEUTRINOS Water phase will allow to look for “invisible” nucleon decay

modes by observation of characteristic gammas.

SN neutrinos for a SN within our galaxy.

See presentation by Belina Von Krosigk on Sunday

Interesting physics by combining with results from HALO (a

dedicated SN detector at SNOLAB) CC and NC

combinations

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COSMOGENICS

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Short and long living isotopes can be produced by cosmogenicactivation of Tellurium – detailed studies by V. Lozza

Isotopes with value larger than 2 MeV and with half-life longer than 20 days have been considered as potential backgrounds. Productions rates were estimated using the program ACTIVIA and the neutron and proton flux parameterization a sea level from Armstrong and Gehrels.

Low energy rand (E<200 MeV) used TENDL database for cross sections where available

Purification factors needed have been determined based on exposure of one year at sea level.

Purification at surface will be able to reduce induced cosmogenicsby a factor larger than 104. Further purification underground and cooling times on the order of month for isotopes produced during transport will also be needed.

With these measures, cosmogenic isotopes are a negligible background contribution


SNO+ ArtFest, May 2014, Kingston Dr. Christine Kraus...

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