Transcript Calorimetry SuperNemo Robert L. Flack University College London On behalf of the SuperNEMO collaboration 14 March 2009 Calorimetry-TIPP09

Calorimetry
SuperNemo
Robert L. Flack
University College London
On behalf of the SuperNEMO collaboration
14 March 2009
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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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2νββ 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 0νββ
decay data.
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0νββ decay
- Beyond
DL = 2!
Phase space
Half-life
Nuclear matrix element
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SM: Total lepton number
violation;
- Most sensitive way to establish
Majorana/Dirac nature of neutrino;
- Most sensitive way to measure
absolute ν mass in a lab environment
(for Majorana ν’s);
- Possible access to ν mass hierarchy
and Majorana CP-violation phases;
-Link to matter-antimatter
asymmetry (leptogenesis).
νe effective mass
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Se82
“Conservative” scenario
SuperNEMO simulations and physics reach
Nd150
Sensitivity
82Se:
T1/2(0n) =(1-2) 1026 yr depending on final mass, background and efficiency
<mn>  0.06 – 0.1 eV (includes uncertainty in T1/2) – MEDEX’07 NME
150Nd:
25 yr <m >  0.045Calorimetry-TIPP09
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2009
TMarch
eV (but deformation not taken into account)
1/2(0n) =5 10
n
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by Matthew Kauer
Calorimeter R&D at SuperNEMO
Good energy resolution is a must!
ln2 . N
T 1/2 (y) > kC.L.
0n
.
e
A
M .t
NBkg . DE
.
M
e
kC.L.
N
t
NBkg
DE
mass (g)
efficiency
confidence level
Avogadro number
time (y)
background events (keV-1.g-1.y-1)
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 R&D at SuperNEMO
SuperNEMO ~ 90 physicists, 12 countries
• currently on 3 year R&D phase (ends late ’09)
R&D on:
• Isotope enrichment
• Drift cell tracker
• Software
• Calorimeter
UCL London
CENBG Bordeaux, LAL Orsay
INR Kiev, ISMA Kharkov
JINR Dubna
Univ. Texas Austin
Isotope
Isotope Mass M
Efficiency e
Internal Bkgs
Energy Resolution
Sensitivity
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82Se
(and/or 150Nd if enrichment possible)
100 - 200 kg
~ 30 %
 10 mBq/kg
4% FWHM @ 3 MeV
T1/2(0nbb) > 1026 y
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<mn> < 0.04 - 0.11 eV
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
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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.
Active shielding (10cm)
– Only ~7,600 3″ or 5″ instead of
15,000 8″ in baseline.
Foil
•Other advantages are:
– Much more compact: 19 m2 floor
area will accommodate ~100 kg of
isotope (20 mg/cm2)
Bars (2.5cm)
– External walls as active shielding
by anti-coincidences
Active shielding
– 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
gap  higher
14scintillator-foil
March 2009
efficiency
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Programme followed for Calorimeter R&D
• 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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by Matthew Kauer
Calorimeter R&D at SuperNEMO
Significant improvements on PM QE!
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Matthew Kauer
8″ Hamamatsu SBA Characterization
33% QE (eventually UBA ~ 45%)
8 dynode chain
linearity > 3000 Npe
1800 Volts
1900 Volts
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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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Matthew Kauer
More realistic setup
Optical contact
EJ200 ~ BC408
Glycerol
Containment Ring
Point-to-point ~ 25.5 cm
Side-to-side ~ 22 cm
Min depth
~ 10 cm
Max depth ~ 18 cm
Surface area ~ 420 cm2
Cargille silica fluid reacts with the PVT!
Hamamatsu
R5912-MOD
Super-Bialkali
8 Dynodes
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Can try 2-propanol
R-index = 1.37 @ 400nm
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8″ PMT @ 1650 V – 25.5x22x10cm HexEJ200~BC408
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 @ 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
Bottom:
Top:
Plastic tube acts
as guide for the
ESR “pipe”
wrapping inside
+20cm
0cm
-20cm
+80cm
+60cm
-40cm
Holes to introduce the
radioactive source
+40cm
-60cm
-80cm
+20cm
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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
2007
2008
2010
2009
2011
2012
2013
2014
NEMO3 Running
SuperNEMO Design Study
BiPo1
Canfranc/LSM
BiPo
construction
BiPo
installation
BiPo running @ Canfranc
SuperNEMO 1st
module construction
Preparation of new
LSM site
construction of
20 modules
Running full detector in 2014
Target sensitivity (0.05-0.1 eV) in 2016
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1-5 SuperNEMO modules
running at Canfranc
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.
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82Se
obtained by centrifugation.
Impossible for 150Nd, only laser
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enrichment.
Qββ 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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ββ decay Background.
is about background suppression
Natural radioactivity:
T1/2(238U, 232Th) ~ 1010 yr
T1/2(0nbb) > 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 < 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
NA
M  e  Tobs
T1/2 (bb0n) > ln 2 

A
N90
SuperNEMO
NEMO-3
100Mo
7 kg
18 %
< 20 mBq/kg
214Bi: < 300 mBq/kg
208Tl:
8% @ 3MeV
isotope
isotope mass M
efficiency e
internal contaminations
208Tl and 214Bi in the bb foil
energy resolution (FWHM)
T1/2(0nbb) > 2 x 1024 y
<mn> < 0.3 – 0.9 eV
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82Se
- baseline
(150Nd if it can be enriched)
100-200 kg
~ 30 %
 2 mBq/kg
if 82Se: 214Bi  10 mBq/kg
208Tl
4% @ 3 MeV
T1/2(0nbb) > 1026 y
<mn> < 0.04 - 0.11 eV
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Choice of site
• Canfranc
Boulby
– 2500 m.w.e
• LS Modane
Canfranc
– 4800 m.w.e
• Boulby
– 2800 m.w.e
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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)
4m
1m
5m
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Top view
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Side view
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Calorimeter R&D
•
•
•
Energy resolution is a combination of energy losses in foil
and calorimeter DE/E
Factor of 2
compared to
Goal: 7-8%/√E  4% at 3 MeV (82Se Qbb)
NEMO3!
Studies:
–
–
–
–
–
Material: organic (plastic or liquid)
Geometry and shape (block, bar)
Size
Reflective coating
PMT
• High QE
• Ultra-low background
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by Matthew Kauer
Quick Comment on Radio-purity
Barium salt used to make glass is chemically same as Radium
Ra226  Rn222 into the tracker volume  Bi214 (Qb ~ 3.3MeV)
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