Brown University, Providence, Rhode Island
Institute for Theoretical and Experimental Physics, Moscow, Russia
Joint Institute for Nuclear Research, Dubna, Russia
Lawrence Berkeley National Laboratory, Berkeley, California
Lawrence Livermore National Laboratory, Livermore, California
Los Alamos National Laboratory, Los Alamos, New Mexico
Oak Ridge National Laboratory, Oak Ridge, Tennessee
Osaka University, Osaka, Japan
Pacific Northwest National Laboratory, Richland, Washington
Queen's University, Kingston, Ontario
Triangle Universities Nuclear Laboratory, Durham, North Carolina
and Physics Departments at Duke University and North Carolina
State University
University of Chicago, Chicago, Illinois
University of South Carolina, Columbia, South Carolina
University of Tennessee, Knoxville, Tennessee
University of Washington, Seattle, Washington
Majorana Neutrinoless Double-Beta
Decay Experiment
GERDA Collaboration Meeting
June 28, 2005
Dubna, Russia
The Majorana 76Ge
0nbb-Decay Experiment
• Based on Ge crystals
– 180 kg 86% 76Ge
– Enriched via centrifugation
Veto Shield
• Modules with 57 crystals each
– Three modules for 180 kg
– Eight modules for 500 kg!
• Maximal use of copper
electroformed underground
• Background rejection methods
–
–
–
–
Granularity
Pulse Shape Discrimination
Single Site Time Correlation
Detector Segmentation
• Underground Lab
– 6000 mwe
– Class 1000
Sliding Monolith
LN Dewar
Inner Shield
57 Detector Module
Conceptual Design of
57 Crystal Module
•
•
•
•
Conventional vacuum cryostat made with electroformed Cu
Three-crystal tower is a module within a module
Allows simplified detector installation & maintenance
Low mass of Cu and other structural materials per kg Ge
40 cm x 40 cm Cryostat
Vacuum jacket
Cap
Cold Plate
Tube
(0.007” wall thickness)
Cold Finger
Ge
(62mm x 70 mm)
1.1 kg Crystal
Tray
(Plastic, Si, etc)
Thermal Shroud
Bottom Closure
1 of 19 Towers
Shield Design
Veto Detector
Sliding Monolith
LN Dewar
Inner Shield
57 Detector Module
•
•
•
•
Allows modular deployment, early results
40 cm bulk Pb, 10 cm ULB shielding
4p veto shield
Sliding 5 ton doors (prototype under ME test)
Background Goals and
Demonstrated Levels
• Simulation connects activity to expected count rate
• Background target: ~1 count/ROI/ton-year
• Three years’ run time with this level (~0.5 ton-year) ~5 x 1026 y
Bkg
Location
Ge Crystals
Purity Issue
68Ge
& 60Co
Activation
Rate
Target
Exposure
Ref.
1
atom/kg/day
100 d
[Avi92]
Target
Mass
Target Purity
Inner Mount
2 kg
Cryostat
38 kg
Achieved
Assay
1 mBq/kg
2-4 mBq/kg
1 mBq/kg
1 mBq/kg
232Th
Cu Shield
310 kg
Small Parts
1 g/crystal
[Arp02]
&
more
recent
work
[Mil92]
Ge Exposure Timeline
• Conservative estimate of 100 days exposure taken
• Doubling this or spallation rate (1 atom/kg/day @
surface) adds only 3% to total rate
Process Step
Minimum
Estimated
Time
Effective Time
(with shield)
Enrichment: (ECP Zelenogorsk)
~90 days
~1 day
Shipping: Zelenogorsk to Oak
Ridge
32 days
3.2 days
Production of metal and initial
refinement:
11 days
11 days
Manufacturer’s zone refinement
14 days
14 days
Crystal growth:
4 days
4 days
Mechanical preparation
3 days
3 days
Detector Fabrication
7 days
7 days
161 days
44.2 days
Shipping Concept: 2m cube
Storage Concept: 4m cube
Total
Granularity
detector-to-detector rejection
~ 40 cm
• Simultaneous signals in two
detectors cannot be 0nbb
• Requires tightly packed Ge
• Successful against:
–
208Tl
and 214Bi
• Supports/small parts (~5x)
• Cryostat/shield (~2x)
– Some neutrons
– Muons (~10x)
• Simulation and validation
with Clover
Pulse Shape Discrimination
Central contact (radial) PSD
• Excellent rejection for
internal 68Ge and 60Co (x4)
• Moderate rejection of
external 2615 keV (x0.8)
• Shown to work well with
segmentation
• Demonstrated capability
– Central contact
– External contacts
• Requires ~25 MHz BW
Time Correlations
•
68Ge
–
–
is worst initial raw background
68Ge
-> 10.367 keV x-ray, 95% eff
68Ga -> 2.9 MeV beta
• Cut for 3-5 half-lives after signals in
the 11 keV X-ray window reduces
68Ga b spectrum substantially
• Independent of other cuts
QEC = 2921.1
3 , 5 t1/2 cut
No cut
Crystal Segmentation
g (“High” Energy)
• Segmentation
– Multiple conductive contacts
– Additional electronics and
small parts
– Rejection greater for more
segments
0nbb
• Background mitigation
– Multi-site energy deposition
• Simple two-segment rejection
• Sophisticated multi-segment
signal processing
• Demonstrated with
– GEANT4 (MaGe) calculations
– MSU experiment
g
60Co
g
g (“Low” Energy)
Segmentation Study
Experiment and Simulation
60Co on the side of the detector
Crystal
Experiment
Crystal
GEANT
1x8
4x8
1x8
4x8
Counts / keV / 106 decays
Simple multiplicity cuts – No PSD
Ultra-Pure Electroformed Cu
• Th chain purity is key
Electroforming copper
– Ra and Th must be eliminated
– Successful Ra ion exchange [C]
– Th ion exchange under
development
C
A
B
• Demonstrated >8000 Th rejection
via electroplating from A->B
30 cm x 30 cm Cryostat
• Starting stock [A] <9 mBq/kg 232Th
• Intensive development of assay to
achieve 1 mBq/kg 232Th of A, B, and
C, and, possibly much less
– Based on ICPMS of nitric etch soln
– Would allow QA of each part
Small Parts: Low-background
Front-end Electronics Package
LFEP
ORTEC
LFEP3
(IGEX)
LFEP4
Material
Circuit Board
(PTFE, Cu, Au)
Mass (grams)
0.32974
JFET
1.5E-4
RhO2 Resistor
5.9E-4
Al wirebond
wire
~2E-5
Silver-Loaded
Epoxy
~1E-4
Design Drivers
Analog Performance Needed for PSD
• Commercial digital spectroscopy
hardware used for current PNNL
PSD has 40 MHz, 14-bit digitization
• Sampling rate is good match with
“easily-achievable” HPGe preamp
bandwidth
Full-energy 1621-keV g (top) and 1592-keV DEP
(bottom) reconstructed current pulses from 120% P-type
Ortec HPGe detector (experimental data)
Response of Ortec HPGe 237P preamplifier
Multi-Parametric
Pulse-Shape Discriminator





Extracts key parameters from each preamplifier output pulse
Sensitive to radial location of interactions and interaction multiplicity
Self-calibrating – allows optimal discrimination for each detector
Discriminator can be recalibrated for changing bias voltage or other variables
Method is computationally cheap, requiring no computed libraries-of-pulses
An old demonstrated result with
12 bit 40 MHz digitization rate
212Bi
DEP of
208Tl
1592.5 keV
1620.6 keV
Experimental Data
228Ac
1587.9 keV
Original
spectrum
Scaled
PSD result
Keeps 80% of the
single-site DEP
(double escape
peak)
Rejects 74% of the
multi-site
backgrounds
(use 212Bi peak as
conservative indicator)
Previous Front-End Results
Rise-times for various experimental
configurations. The pulser rise-time for
these tests was ~15 ns.
Rise-time with
pulser input
(10%-90%)
Detector type
Commercial HPGe detector, 30% relative
efficiency, Princeton Gamma-Tech.
30.0 ns
Low-background detector and cryostat
with original IGEX cooled FET assembly,
30% relative efficiency.
43.0 ns
Low-background detector and cryostat
with final IGEX cooled FET assembly,
30% relative efficiency.
37.5 ns
IGEX low-background detector
cryostat with original cooled
assembly and internal wiring.
and
FET
IGEX low-background detector and
cryostat with final IGEX cooled FET
assembly and Beldin type 8700 coaxial
cable for signal connections.
70 ns
32.5 ns
All tests used PGT RG-11 as preamp
back-end
Disasters Do Happen
Punishment for yielding 120 ns
10% - 90% performance
• We didn’t really like that FET anyway…
Current LFEP Module Performance
(2N4356 FET w/92cm leads)
40 ns
1090%
outpu
t
pulse
input
powe
r
outpu
t
powe
r
input
pulse
25
MHz
Background Goals
Gross and Net Rates for
Important Isotopes
Background
Source
Counts in ROI per t-y
60
Ge
Co
2.54
1.22
0.01
0.02
208
214
60
Tl
Bi
Co
0.12
0.03
0.26
0.01
0.00
0.00
0.77
0.16
0.58
0.22
0.04
0.00
2.28
0.30
0.02
0.64
0.06
0.00
0.18
0.04
0.34
0.02
0.01
0.00
cosmic
muons
activity
(,n)
0.03
1.33
0.003
0.003
0.18
0.003
Total Est.
Background
(per t-y)
Counts in ROI
68
Germanium
Inner Mount
Cryostat
Copper
Shield
Small Parts
Gross
Net
Gross
Net
Gross
Net
Gross
Net
Gross
Net
External
Sources
Gross
Net
2n bb-decay
TOTAL SUM
0.03
0.01
0.26
0.70
Dominated by
232Th in Cu
0.03
0.18
< 0.01
1.21
At this level,
we might not
get a count in
a 3 year run!
Cuts vs. Background Estimates
16
0vbb
14
External
Small parts
12
Cu Shield
Counts / ROI / ty
Cryostat
10
Inner Mount
Crystals
8
6
4
2
0
Raw 0vbb
Final 0vbb
Raw
Granularity
PSD
SSTC
Segmentation
Construction vs. Operations
45.00
68Ge
12000
build up and decay
40.00
10000
35.00
External
Small parts
Cu Shield
Cryostat
Inner Mount
Crystals
30.00
25.00
8000
kg/quarter
atoms 68
6000
4000
20.00
2000
15.00
0
80% of total 68Ge
has decayed
0
365
730
1095 1460 1825 2190 2555 2920
10.00
5.00
0.00
Raw
Construction
Raw
Granularity
Segmentation
PSD
Time
Correlation
Majorana Sensitivity vs. Time
• 180 kg 86% 76Ge operated for 3 years
• 0.46 t-y of 76Ge or 0.54 t-y total Ge
Effect of background
0 cts/ROI/ty: Ideal
1 cts/ROI/ty: target
8 cts/ROI/ty: certain
(IGEX levels with new
data cuts applied)
A Recent Claim
Klapdor-Kleingrothaus H V, Krivosheina I V, Dietz A and
Chkvorets O, Phys. Lett. B 586 198 (2004).
Used five 76Ge crystals, with a total of
10.96 kg of mass, and 71 kg-years of data.
1/2 = 1.2 x 1025 y
0.24 < mv < 0.58 eV (3 sigma)
Background level depends on
intensity fit to other peaks.
Expected signal in Majorana
(for 0.456 t-y)
135 counts
With a background
Goal: < 1 cnt in the ROI
(Demonstrated < 8 cnts in the ROI)
Reference Schedule
Year
20050
Year
20061
Year
20072
Year
20083
Year
20094
Year
20105
Year
20116
Year
20127
Year
20138
Year
20149 Year
201510 Year
201611
Proposal/CD-0 Package
CD-0/Approve Mission Need
R&D Module
R&D module
Conceptual Design
Site Selection
CD-1/Approve Preliminary Baseline Range
Construction
Preliminary Design (PED)
CD-2/3a/Approve Baseline/Long-Lead Procurement
3a: Prepare and Ship Ge
Enriched
GeSite Preparation
CD-3 Start Construction
Module
1
Receive Ge
Testing
Fabricate Detectors
Electroforming
Production Cryostats
Module
2
Testing
Assemble
Experimental Apparatus/Shielding
Assemble Detectors into Cryostat/Shield
Module 3
Testing
Full Detector Operations
Pre-Operational Testing
CD-4/Start of Operations
Operations
Decommissioning
Majorana Sensitivity: Realistic runtime
GERDA Relationship
• GERDA Collaboration using 20 kg of existing (IGEX+HM) 76Ge
crystals (Phase 1) and ~35kg new Ge (Phase 2) to achieve
sensitivity past KKDC
• New approach for Phase 1 & 2
– Ge immersed in cryogen in large tank in LNGS
• Signed MOU to cooperate in early years and merge for unified
ultimate thrust, using most effective technologies and concepts
• Continued careful cooperation and coordination very important!
GERDA P1 20 kg
GERDA P2 35 kg
Joint experiment ~1000 kg
Majorana 180 kg
Majorana Summary
• As in Gerda, backgrounds are key
• We have begun proposing a modular plan
for intermediate (180 kg) scale with
potential for expansion to ton scale
• The NuSAG Committee is expected to
recommend a double-beta decay research
plan by mid to late July
The Majorana Collaboration
Brown University, Providence, Rhode Island
Michael Attisha, Rick Gaitskell, John-Paul Thompson
Institute for Theoretical and Experimental Physics, Moscow, Russia
Alexander Barabash, Sergey Konovalov, Igor Vanushin, Vladimir
Yumatov
Joint Institute for Nuclear Research, Dubna, Russia
Viktor Brudanin, Slava Egorov, K. Gusey, S. Katulina, Oleg Kochetov,
M. Shirchenko, Yu. Shitov, V. Timkin, T. Vvlov, E. Yakushev, Yu.
Yurkowski
Lawrence Berkeley National Laboratory, Berkeley, California
Yuen-Dat Chan, Mario Cromaz, Martina Descovich, Paul Fallon, Brian
Fujikawa, Bill Goward, Reyco Henning, Donna Hurley, Kevin Lesko,
Paul Luke, Augusto O. Macchiavelli, Akbar Mokhtarani, Alan Poon,
Gersende Prior, Al Smith, Craig Tull
Lawrence Livermore National Laboratory, Livermore, California
Dave Campbell, Kai Vetter
Los Alamos National Laboratory, Los Alamos, New Mexico
Mark Boulay, Steven Elliott, Gerry Garvey, Victor M. Gehman,
Andrew Green, Andrew Hime, Bill Louis, Gordon McGregor,
Dongming Mei, Geoffrey Mills, Larry Rodriguez, Richard
Schirato, Richard Van de Water, Hywel White, Jan Wouters
Oak Ridge National Laboratory, Oak Ridge, Tennessee
Cyrus Baktash, Jim Beene, Fred Bertrand, Thomas V. Cianciolo, David
Radford, Krzysztof Rykaczewski
Osaka University, Osaka, Japan
Hiroyasu Ejiri, Ryuta Hazama, Masaharu Nomachi
Pacific Northwest National Laboratory, Richland, Washington
Craig Aalseth, Dale Anderson, Richard Arthur, Ronald Brodzinski, Glen
Dunham, James Ely, Tom Farmer, Eric Hoppe, David Jordan, Jeremy
Kephart, Richard T. Kouzes, Harry Miley, John Orrell, Jim Reeves,
Robert Runkle, Bob Schenter, Ray Warner, Glen Warren
Queen's University, Kingston, Ontario
Marie Di Marco, Aksel Hallin, Art McDonald
Triangle Universities Nuclear Laboratory, Durham, North Carolina and
Physics Departments at Duke University and North Carolina State
University
Henning Back, James Esterline, Mary Kidd, Werner Tornow, Albert
Young
University of Chicago, Chicago, Illinois
Juan Collar
University of South Carolina, Columbia, South Carolina
Frank Avignone, Richard Creswick, Horatio A. Farach, Todd Hossbach,
George King
University of Tennessee, Knoxville, Tennessee
William Bugg, Yuri Efremenko
University of Washington, Seattle, Washington
John Amsbaugh, Tom Burritt, Jason Detwiler, Peter J. Doe, Joe
Formaggio, Mark Howe, Rob Johnson, Kareem Kazkaz, Michael Marino,
Sean McGee, Dejan Nilic, R. G. Hamish Robertson, Alexis Schubert,
John F. Wilkerson