majorana neutrinoless double-beta decay experiment gerda collaboration meeting june 28, 2005 dubna,...
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Majorana Neutrinoless Double-Beta Decay Experiment
GERDA Collaboration Meeting
June 28, 2005
Dubna, Russia
Brown University, Providence, Rhode IslandInstitute for Theoretical and Experimental Physics, Moscow, RussiaJoint Institute for Nuclear Research, Dubna, RussiaLawrence Berkeley National Laboratory, Berkeley, CaliforniaLawrence Livermore National Laboratory, Livermore, CaliforniaLos Alamos National Laboratory, Los Alamos, New MexicoOak Ridge National Laboratory, Oak Ridge, TennesseeOsaka University, Osaka, Japan
Pacific Northwest National Laboratory, Richland, WashingtonQueen's University, Kingston, OntarioTriangle Universities Nuclear Laboratory, Durham, North Carolina and Physics Departments at Duke University and North Carolina State UniversityUniversity of Chicago, Chicago, IllinoisUniversity of South Carolina, Columbia, South CarolinaUniversity of Tennessee, Knoxville, TennesseeUniversity of Washington, Seattle, Washington
The Majorana 76Ge 0-Decay Experiment
• Based on Ge crystals– 180 kg 86% 76Ge– Enriched via centrifugation
• 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
57 Detector Module
Veto Shield
Sliding Monolith
LN Dewar
Inner Shield
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
CapCap
Tube (0.007” wall thickness)Tube (0.007” wall thickness)
Ge(62mm x 70 mm)Ge(62mm x 70 mm)
Tray(Plastic, Si, etc)Tray(Plastic, Si, etc)
Cold PlateCold Plate
1.1 kg Crystal 1.1 kg Crystal
Thermal Shroud
Vacuum jacketVacuum jacket
Cold Finger
Bottom Closure1 of 19 Towers
40 cm x 40 cm Cryostat
Shield Design
• Allows modular deployment, early results• 40 cm bulk Pb, 10 cm ULB shielding• 4 veto shield• Sliding 5 ton doors (prototype under ME test)
Veto Detector
Sliding Monolith
LN Dewar
Inner Shield
57 Detector Module
Veto Detector
Sliding Monolith
LN Dewar
Inner Shield
57 Detector Module
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
BkgLocation
Purity IssueActivation
RateTarget
ExposureRef.
Ge Crystals 68Ge & 60Co1
atom/kg/day100 d [Avi92]
Target Mass
Target PurityAchieved
Assay
Inner Mount
232Th
2 kg
1 Bq/kg 2-4 Bq/kg
[Arp02]&
more recentwork
Cryostat 38 kg
Cu Shield 310 kg
Small Parts 1 g/crystal 1 mBq/kg 1 mBq/kg [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 rateProcess Step Minimum
EstimatedTime
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
Total 161 days 44.2 days
Shipping Concept: 2m cube
Storage Concept: 4m cube
Granularitydetector-to-detector rejection
• Simultaneous signals in two detectors cannot be 0
• 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
~ 40 cm
Pulse Shape Discrimination
• 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
Central contact (radial) PSD
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 spectrum substantially
• Independent of other cuts
No cut
3 , 5 t1/2 cut
QEC = 2921.1
Crystal Segmentation
• Segmentation– Multiple conductive contacts– Additional electronics and
small parts– Rejection greater for more
segments• Background mitigation
– Multi-site energy deposition• Simple two-segment rejection• Sophisticated multi-segment
signal processing
• Demonstrated with– GEANT4 (MaGe) calculations– MSU experiment
60Co
(“Low” Energy)
(“High” Energy)
Segmentation Study Experiment and Simulation
60Co on the side of the detector
Simple multiplicity cuts – No PSD
Experiment
GEANT
Crystal
1x8
4x8
Cou
nts
/ ke
V /
106
deca
ys
Crystal
1x84x8
Ultra-Pure Electroformed Cu
• Th chain purity is key– Ra and Th must be eliminated– Successful Ra ion exchange [C]– Th ion exchange under
development
• Demonstrated >8000 Th rejection via electroplating from A->B
• Starting stock [A] <9 Bq/kg 232Th
• Intensive development of assay to achieve 1 Bq/kg 232Th of A, B, and C, and, possibly much less– Based on ICPMS of nitric etch soln– Would allow QA of each part
Electroforming copper
A B
C
A B
C
30 cm x 30 cm Cryostat30 cm x 30 cm Cryostat
Small Parts: Low-background Front-end Electronics Package
LFEP
Material Mass (grams)
Circuit Board (PTFE, Cu, Au)
0.32974
JFET 1.5E-4
RhO2 Resistor 5.9E-4
Al wirebond wire
~2E-5
Silver-Loaded Epoxy
~1E-4
ORTEC LFEP3 (IGEX)
LFEP4
Design DriversAnalog 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 (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
228Ac1587.9 keV
DEP of 208Tl
1592.5 keV
212Bi1620.6 keV
Keeps 80% of the single-site DEP (double escape peak)Rejects 74% of the multi-site backgrounds (use 212Bi peak as conservative indicator)
Experimental Data
Original spectrum
Scaled PSD
result
Previous Front-End Results
Detector typeRise-time with pulser input (10%-90%)
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 and cryostat with original cooled FET assembly and internal wiring.
70 ns
IGEX low-background detector and cryostat with final IGEX cooled FET assembly and Beldin type 8700 coaxial cable for signal connections.
32.5 ns
Rise-times for various experimental configurations. The pulser rise-time for these tests was ~15 ns.
All tests used PGT RG-11 as preamp back-end
Disasters Do Happen
• We didn’t really like that FET anyway…
Punishment for yielding 120 ns 10% - 90% performance
Current LFEP Module Performance(2N4356 FET w/92cm leads)
input powe
r
output
power
input pulse
output
pulse
25 MHz
40 ns 10-
90%
Background Goals
Gross and Net Rates for Important Isotopes
Total Est. Background
(per t-y)
Background Source
Counts in ROI per t-y Counts in ROI 68Ge 60Co Germanium Gross 2.54 1.22
Net 0.01 0.02 0.03 208Tl 214Bi 60Co
Gross 0.12 0.03 0.26 Inner Mount Net 0.01 0.00 0.00 0.01
Gross 0.77 0.16 0.58 Cryostat Net 0.22 0.04 0.00 0.26
Gross 2.28 0.30 0.02 Copper Shield Net 0.64 0.06 0.00 0.70
Gross 0.18 0.04 0.34 Small Parts Net 0.02 0.01 0.00 0.03
muons
cosmic activity
(,n)
Gross 0.03 1.33 0.003
External Sources
Net 0.003 0.18 0.003 0.18 2-decay < 0.01
TOTAL SUM 1.21
Dominated by 232Th in Cu
At this level, we might not get a count in a 3 year run!
Cuts vs. Background Estimates
0
2
4
6
8
10
12
14
16
Raw 0vbb Final 0vbb Raw Granularity PSD SSTC Segmentation
Co
un
ts /
RO
I /
ty
0vbb
External
Small parts
Cu Shield
Cryostat
Inner Mount
Crystals
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
RawConstruction
Raw Granularity Segmentation PSD TimeCorrelation
External
Small parts
Cu Shield
Cryostat
Inner Mount
Crystals
Construction vs. Operations
0
2000
4000
6000
8000
10000
12000
0 365 730 1095 1460 1825 2190 2555 2920
kg/quarter
atoms 68
68Ge build up and decay
Ops Begins
80% of total 68Ge has decayed
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: Ideal1 cts/ROI/ty: target8 cts/ROI/ty: certain(IGEX levels with new data cuts applied)
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 y0.24 < mv < 0.58 eV (3 sigma)
A Recent Claim
Background level depends on intensity fit to other peaks.
Klapdor-Kleingrothaus H V, Krivosheina I V, Dietz A and Chkvorets O, Phys. Lett. B 586 198 (2004).
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)
Year 0 Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 7 Year 8 Year 9 Year 10 Year 11
Proposal/CD-0 Package
CD-0/Approve Mission Need
R&D module
Conceptual Design
Site Selection
CD-1/Approve Preliminary Baseline Range
Preliminary Design (PED)
CD-2/3a/Approve Baseline/Long-Lead Procurement
3a: Prepare and Ship Ge
Site Preparation
CD-3 Start Construction
Receive Ge
Fabricate Detectors
Electroforming Production Cryostats
Assemble Experimental Apparatus/Shielding
Assemble Detectors into Cryostat/Shield
Pre-Operational Testing
CD-4/Start of Operations
Full Detector Operations
Decommissioning
Reference Schedule
R&D Module
EnrichedGe
Module 1Testing
Module 2Testing
Module 3Testing
Operations
Construction
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016
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
Majorana 180 kg
Joint experiment ~1000 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
Brown University, Providence, Rhode IslandMichael 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, RussiaViktor 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, CaliforniaYuen-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, CaliforniaDave Campbell, Kai Vetter
Los Alamos National Laboratory, Los Alamos, New MexicoMark 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, TennesseeCyrus Baktash, Jim Beene, Fred Bertrand, Thomas V. Cianciolo,
David Radford, Krzysztof Rykaczewski
Osaka University, Osaka, JapanHiroyasu Ejiri, Ryuta Hazama, Masaharu Nomachi
Pacific Northwest National Laboratory, Richland, WashingtonCraig 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, OntarioMarie Di Marco, Aksel Hallin, Art McDonald
Triangle Universities Nuclear Laboratory, Durham, North Carolina and Physics Departments at Duke University and
North Carolina State UniversityHenning Back, James Esterline, Mary Kidd, Werner Tornow,
Albert Young
University of Chicago, Chicago, IllinoisJuan Collar
University of South Carolina, Columbia, South CarolinaFrank Avignone, Richard Creswick, Horatio A. Farach, Todd
Hossbach, George King
University of Tennessee, Knoxville, TennesseeWilliam Bugg, Yuri Efremenko
University of Washington, Seattle, WashingtonJohn 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
The Majorana Collaboration