Majorana Neutrinoless Double- Beta Decay Experiment GERDA Collaboration Meeting June 28, 2005 Dubna, Russia 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
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Majorana Neutrinoless Double-Beta Decay Experiment GERDA Collaboration Meeting June 28, 2005 Dubna, Russia Brown University, Providence, Rhode Island Institute.
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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
• 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
• 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%)
• 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,
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