Calorimetry SuperNemo

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CalorimetrySuperNemo

• Robert L. Flack
• University College London
• On behalf of the SuperNEMO collaboration

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Overview

• SuperNEMO
• Neutrino mass
• Double beta decay
• The collaboration
• Results
• Scintillator blocks
• Scintillator bars
• The future
• Pre-production module
• Summary

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What is the absolute mass scale? How far above
zero is the pattern?




Oscillation data
Cosmological data
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Do neutrinos have Majorana masses?
Majorana masses for quarks and charged leptons
are forbidden due to charge conservation.
If neutrinos do have Majorana masses then they
must have a very different origin to quark and
charged lepton masses.
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2?ßß decay

• Standard model process
• Valuable measurement in its own right
• Input into nuclear matrix element (NME)
  calculations
• Accurate estimates of NMEs are crucial in the
  analysis of 0?ßß decay data.

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0?ßß decay

• - Beyond SM Total lepton number
• violation
• - Most sensitive way to establish
• Majorana/Dirac nature of neutrino
• - Most sensitive way to measure
• absolute ? mass in a lab environment
• (for Majorana ?s)
• - Possible access to ? mass hierarchy
• and Majorana CP-violation phases
• Link to matter-antimatter asymmetry
  (leptogenesis).

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SuperNEMO simulations and physics reach
Se82
Conservative scenario
Nd150
Sensitivity
82Se T1/2(0n) (1-2) 1026 yr depending on final
mass, background and efficiency ltmngt ? 0.06 0.1
eV (includes uncertainty in T1/2) MEDEX07
NME 150Nd T1/2(0n) 5 1025 yr ltmngt ? 0.045 eV
(but deformation not taken into account)
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Calorimeter RD at SuperNEMO
by Matthew Kauer
Good energy resolution is a must!
M mass (g) e efficiency kC.L.
confidence level N Avogadro number t
time (y) NBkg background events
(keV-1.g-1.y-1) DE energy resolution (keV)
Even with ideal M, Nbkg, e ? 2n and 0n mix at
low DE
8 FWHM
12 FWHM
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Calorimeter RD at SuperNEMO

• SuperNEMO 90 physicists, 12 countries
• currently on 3 year RD phase (ends late 09)

• RD on
• Isotope enrichment
• Drift cell tracker
• Software
• Calorimeter

UCL London CENBG Bordeaux, LAL Orsay INR Kiev,
ISMA Kharkov JINR Dubna Univ. Texas Austin
82Se (and/or 150Nd if enrichment possible) 100
- 200 kg 30 ? 10 mBq/kg 4 FWHM _at_ 3
MeV T1/2(0nbb) gt 1026 y ltmngt lt 0.04 - 0.11 eV
Isotope Isotope Mass M Efficiency e Internal
Bkgs Energy Resolution Sensitivity
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SuperNEMO base design (Energy resolution 7)
Single sub-module with 5-7 kg of isotope
20 sub-modules for 100 kg of isotope
surrounded by water shielding
Foil
Total 40-60k geiger channels for tracking
10-20k PMTs
Shielding
Problem with the low radio-purity of the glass of
the PMTs
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Alternative design using scintillator bars
(Energy resolution 10)

• To overcome the radio-purity problem the number
  of PMTs is halved and they are situated away from
  the main detector volume.
• Only 7,600 3? or 5? instead of 15,000 8? in
  baseline.
• Other advantages are
• Much more compact 19 m2 floor area will
  accommodate 100 kg of isotope (20 mg/cm2)
• External walls as active shielding by
  anti-coincidences
• Reduced cost of PMTs 8.5M - baseline, 1.25M -
  bars (if 3)
• More options for external bkg suppression, TOF
  can be relaxed (possibly). Hence may try smaller
  scintillator-foil gap ? higher efficiency

Active shielding (10cm)
Foil
Bars (2.5cm)
Active shielding
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Programme followed for Calorimeter RD

• Energy resolution is a combination of energy
  losses in foil and calorimeter DE/E
• Two routes pursued
• 8? PMT plastic block
• 2m plastic scintillator bars.
• PMTs
• Working closely with Hamamatsu
• Real breakthrough in high-QE PMTs of 43 QE
• First large (8?) high-QE Hamamatsu PMT was
  delivered to UCL for testing last year
• Involvement in ultra-low background PMT
  development.
• Enhanced specular reflectors available, 98
  reflectivity instead of usual 93.
• Decision on calorimeter design in June 2009.

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Calorimeter RD at SuperNEMO
Significant improvements on PM QE!
by Matthew Kauer
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Matthew Kauer
8? Hamamatsu SBA Characterization
33 QE (eventually UBA 45) 8 dynode
chain linearity gt 3000 Npe
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Excellent first result with plastic
scintillator Using 207Bi source
by Matthew Kauer
976keV
DE/E 6.5 at 1 MeV ? 3.8 at 3 MeV
207Bi conversion electron source
BC404 scintillator wrapped in Teflon
Hamamatsu high-QE PMT
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More realistic setup Optical contact
Matthew Kauer
Point-to-point 25.5 cm Side-to-side 22
cm Min depth 10 cm Max depth 18
cm Surface area 420 cm2
EJ200 BC408
Glycerol
Containment Ring
Cargille silica fluid reacts with the PVT!
Hamamatsu R5912-MOD Super-Bialkali 8 Dynodes
Can try 2-propanol R-index 1.37 _at_ 400nm
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8? PMT _at_ 1650 V 25.5x22x10cm HexEJ200BC408 ESR
sides, Mylar face, Glycerol coupling fluid
Tested hexagonal and cylindrical shape and got
similar results
For mechanical reasons we will use hexagonal
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Matthew Kauer
Tested using 90Sr source _at_ 1MeV
7.6 !!
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Scintillator bars

• Scintillator bars from ELJEN, Texas
• EJ-200 (analogue of BC408)
• 200cm length x 10cm width, tapered at ends to
  6.5cm width to fit 3 PMTs at 45 angle
• 3? Hamamatsu SBA-select tubes ( 40 QE)
• Wrapped ReflecTech ESR
• Thickness 100µm
• Surface density 11.9mg/cm2
• 15 - 20 keV loss in ESR

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Scintillator bars
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Laboratory setup
Plastic tube acts as guide for the ESR pipe
wrapping inside
Holes to introduce the radioactive source
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Tests of mechanical structure and optical contact
of the PMTs in differing orientations
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Summary

• SuperNEMO 3 year Design Study nearly finished
• For the baseline
• PVT blocks with 8? PMTs
• 40 High-QE PMTs
• 98 specular reflectors
• 10K photons/MeV scintillator (low Z)
• Unprecedented resolution for low Z scintillator
  (7 FWHM 1MeV)
• Alternative design using 2m scintillator bars
• 10 resolution
• 450 ps timing resolution,
• want to reduce this 250ps
• We will achieve the target sensitivity of 50-100
  meV

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Backup slides
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Schedule Summary
2014
NEMO3 Running
SuperNEMO Design Study

BiPo1 Canfranc/LSM

BiPo installation

BiPo running _at_ Canfranc
SuperNEMO 1st module construction
Preparation of new LSM site
construction of 20 modules
1-5 SuperNEMO modules running at Canfranc
Running full detector in 2014 Target sensitivity
(0.05-0.1 eV) in 2016
SuperNEMO modules installation at new LSM
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Choice of Isotope

• Criteria of choice
• High Qbb value
• Phase space G0n
• 2nbb half-life
• natural abundance
• enrichment possibilities.

Purification of 4kg of 82Se underway (INL,
US). Enrichment of 150Nd possible.
82Se obtained by centrifugation. Impossible for
150Nd, only laser enrichment.
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Qßß for some isotopes
Q-values 48Ca, 4.27MeV 150Nd, 3.37MeV 100Mo,
3.03MeV 82Se, 3.00MeV 136Xe, 2.48MeV 76Ge, 2.04MeV
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ßß decay is about background suppression
Background.
Natural radioactivity T1/2(238U, 232Th) 1010
yr T1/2(0nbb) gt 1025 yr 238U and 232Th produce
214Bi (Qb 3.27 MeV) and 208Tl(Qb 4.99
MeV) Radon! Cosmogenic activitity Underground
is a must Due to tracking, for SuperNEMO the
main focus is on source (foil) purity. Must be
super-duper-ultra low lt 10 mBq/kg! (For reference
humans 10-100 Bq/kg

typical materials 1Bq/kg) But how to
measure these levels?!


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From NEMO-3 to SuperNEMO
M ? e ? Tobs
NA
T1/2 (bb0n) gt ln 2 ?
?
N90
A
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30
efficiency ?
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Choice of site

• Canfranc
• 2500 m.w.e
• LS Modane
• 4800 m.w.e
• Boulby
• 2800 m.w.e

Boulby
Canfranc
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SuperNEMO preliminary design
Single module (baseline design)
Planar geometry. 20 modules for 100 kg
Source (40 mg/cm2) 12m2
, tracking volume (2-3k Geiger channels).
calorimeter (0.5-1k ch)
Total 40-60k geiger channels
for tracking 10-20k PMTs (3k if
scintillator bars design)
4 m
1 m
5 m
Top view
Side view
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Calorimeter RD

• Energy resolution is a combination of energy
  losses in foil and calorimeter DE/E
• Goal 7-8/vE ? 4 at 3 MeV (82Se Qbb)
• Studies
• Material organic (plastic or liquid)
• Geometry and shape (block, bar)
• Size
• Reflective coating
• PMT
• High QE
• Ultra-low background

Factor of 2 compared to NEMO3!
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Quick Comment on Radio-purity
by Matthew Kauer
Barium salt used to make glass is chemically same
as Radium Ra226 ? Rn222 into the tracker volume ?
Bi214 (Qb 3.3MeV)