Poster - Indico

The SNO+ Project
Laura Segui, for the SNO+ Collaboration
[email protected], Oxford University, United Kingdom
Deck + DAQ
 SNO+: successor of SNO (Sudbury Neutrino Observatory)
• Light water  filling now
Nucleon decay
 Located at SNOLAB, in the Creighton mine, Sudbury, Canada
• Scintillator loading (summer 2015)
Backgrounds
• 2070 m (6000 m.w.e.) depth
• Pure scintillator phase
Backgrounds & solar ν
• ~70 muons/day
• Te-loaded scintillator (end2015)
0νββ of 130Te
Ropes
• Class-2000 clean room
Acrylic
Vessel
 Primary goal: search for the neutrinoless double beta decay
Φ 12 m
(0νββ) of 130Te with Te-loaded liquid scintillator
5 cm thick
Water
shielding:
•1700 t inner
•5300 t outer
Urylon liner:
Rn seal
 
~9500 PMTs
54%
coverage
~780 t
Liquid organic
scintillator + PPO
ββ2ν standard
process, already
observed
ββ0ν process BSM,
only possible if ν is
Majorana   
ββ0ν would provide crucial
information on:
• Neutrino nature (Dirac or
Majorana)
•Neutrino mass hierarchy
(inverse or direct)
Reactor ν
Supernova
SNO+ Physics Program and schedule
Geo-ν
The SNO+ Detector
Te-loaded scintillator
Mixture:
LAB + PPO (2g/L) + wavelength shifter + H20 + Surfactant +
+ Natural Te : initial phase 0.3% nat. Te (~790 kg of 130Te)
Advantages:
• Long attenuation length, No inherent optical absorption lines
• High light yield (~10000γ/MeV)
• α-β separation decay time
• Te high natural abundance in 130Te (34%)
• 2νββ rate is low
Purification Plant and backgrounds
• LAB purification plant to reach the following radioactive
levels and to be vacuum leak tightness (<10-9 mbar*l/s of He)
Backgrounds
Purification plant methods
 8B solar neutrino and 2νββ: can be reduced
improving energy resolution
 Multi-stage distillation
• 6.8x10-18 g/g in 232Th <1 c/day in 208Tl
 Removes heavy metals
~1.2c/day in 208Ac
 External: gammas from water, PMTs, PSUP and
rock
 Improves UV transparency
• 1.6x10-17 g/g in 238U  13.4 c/day in 214Bi, in 234-mPa
 Dual-stream PPO distillation
and in 222Rn 2 orders of magnitude less than in SNO
 Fiducialisation & Timing cuts
 N2/steam stripping
• 10-18 g/g in 40K
 Removes Rn, Kr, Ar and O2
Noble gas impurities target levels
 Cosmogenics: Te purification (right) & UG cooling
time
Distillation and
Stripping columns
 Internal U/Th chain
 Water extraction
• 10-25 g/g in 85Kr
 In-situ analysis: Bi-Po α´s, expected 100%
rejection if Bi-Po falls in separated trigger windows.
Small fraction pile-up in RoI
 Metal scavengers
 Removes Bi, Pb, Ra, Ac andTh
(factor 800 in single pass)
 0.2% pile up of 214Bi-214Po further reduction
factor of 50 based on time structure
 total rejection >99.99%
 Microfiltration
Scavengers columns
 Removes dust
 69% pile-up of 212Bi-212Po  further reduction
factor of 50  total rejection of 98.5%
 RECIRCULATION
While the detector is operational scintillator can be recirculated
@ 150 LPM (full detector in 4 days) to provide repurification as
necessary
Pipe model
Calibration Systems
Source
Particle
Energy (MeV)
Tag
AmBe
n, γ
2.2, 4.4
Coinc.
16N
γ
6.1
Yes
• Using external sources and
24Na
γ
1.3, 2.7
Yes
• Internal backgrounds
48Sc
γ
1.0, 1.2, 1.3
No
57Co
γ
0.122
No
60Co
γ
1.2, 1.4
Yes
90Y
β
2.3
No
• Characterize the detector
response with different particles
• Important detailed understanding of PMTs  for analysis
• PMTs and electronics response
• Reconstruction
• Energy resolution,….
• Some external sources will only
be used in either the water or
scintillator phase
• Radioactive + optical sources
• Source deployment: keep to a minimum
TELLIE
Optical Calibration
• Measure the parameters describing the
propagation of light in the detector media
(Embedded LED Light Injection Entity)
• Can be run continuously (low rate,
~Hz) or at high rate (~kHZ) for
calibration runs
• Three subsystems (TELLIE,
SMELLIE, AMELLIE)
The Umbilcal Retrieval Mechanism
allows to deploy the calibration source
to specific locations in the detector.
SMELLIE
ELLIE
• Inject light from the PMT array to the
detector using optical fibres
removed by a
factor >104 after
two passes
Commisioning of ELLIE systems in air (March 2014)
• 92 PSUP positions, straight across, wide
angle emission,
• 510 nm LEDs
• Timing calibration of the PMTs
• Gain calibration and optical transparency
• Using external sources
60Co
 Reducing Radon ingress with a New cover gas
system Commissioned
Radioactive sources
• Understanding of entire detector response for E range (0.1- 10MeV)
1. 2 Surface passes:
 Dissolve Te(OH)6 in water
 Recrystallize using nitric acid
 Rinse with ethanol
>104reduction
2. 2 Underground passes:
 Dissolve in warm water (80°C)
 Cool to recrystallize thermally
>102reduction
 Purification
 Removes Ra, K and Bi
• 10-24 g/g in 39Ar
Te Purification Strategy
• 4 injection PSUP positions, 3 angles,
narrow angle emission
• Laser of 375, 405, 440, 500 nm
• Measurement of scattering properties of the
detector medium
AMELLIE
• 4 injection PSUP positions, 2 angles
per position
• Ultra-fast LEDs of 400, 520nm
• Monitoring of optical attenuation length
Hit map of the PMT array of a TELLIE
commissioning run in air
Event display showing the integral of many events for a SMELLIE
run in air. The direct, backscattered and reflection in the AV light
spots for one laser can be identified
Conclusions and SNO+ Future
Cerenkov Source
Laserball
 8Li source from SNO  Cerenkov light source
 Commissioning runs in air show good performance of electronics and calibration systems
 8Li  8Be + β- + ν (Qβ ~13 MeV); 8Be  2α
Consists of a light diffusing sphere coupled to a
N2 laser
 Water filling on-going
 β- enters acrylic wall, produces Cerenkov light and stops
in the acrylic
 The wavelengths can be altered by inserting
special dyes into the beamline
 α produce scintillation light tag the event
 Upgrade SNO design (NIM A 554 (2005) 255-265)
 PMT hit timing, and direction distributions studies
- A prototype has
been successfully
constructed
- The final source
is under
construction now.
 Good understanding of backgrounds and rejection techniques studied
Future options to increase sensitivity
 Higher loading
 Fully synthetic quartz  radioactively pure
(10 cm diameter)
 Reduced neck diameter and optimized laser
dyes
 Calibrate PMT (and light concentrator) angular
response
 Scintillator extinction length
 Increasing light yield  energy resolution
 Improving loading technique
- The final laserball
is being
constructed now
 Higher QE PMTs
 Using a low background bag to reduce externals
0.3%
0.5%
1%
3%
5%