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Majorana Neutrinoless Double-Beta Decay Experiment

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

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Majorana Neutrinoless Double-Beta Decay Experiment

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  1. 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

  2. Veto Shield Sliding Monolith LN Dewar Inner Shield 57 Detector Module The Majorana 76Ge 0nbb-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

  3. Vacuum jacket Cold Plate Cold Finger 1.1 kg Crystal Thermal Shroud Bottom Closure 1 of 19 Towers 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 Cap Tube (0.007” wall thickness) Ge (62mm x 70 mm) Tray (Plastic, Si, etc)

  4. Shield Design • Allows modular deployment, early results • 40 cm bulk Pb, 10 cm ULB shielding • 4p veto shield • Sliding 5 ton doors (prototype under ME test)

  5. 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

  6. 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 Shipping Concept: 2m cube Storage Concept: 4m cube

  7. Granularitydetector-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

  8. 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

  9. 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

  10. g (“High” Energy) 0nbb g g 60Co g (“Low” Energy) 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

  11. Segmentation Study Experiment and Simulation 60Co on the side of the detector Simple multiplicity cuts – No PSD Experiment Crystal Counts / keV / 106 decays Crystal GEANT 1x8 1x8 4x8 4x8

  12. Electroforming copper C C A A B B 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 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 30 cm x 30 cm Cryostat

  13. Small Parts: Low-background Front-end Electronics Package LFEP ORTEC LFEP3 (IGEX) LFEP4

  14. 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 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

  15. 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

  16. 212Bi1620.6 keV DEP of 208Tl1592.5 keV 228Ac1587.9 keV An old demonstrated result with 12 bit 40 MHz digitization rate Keeps 80% of the single-site DEP (double escape peak) Experimental Data Rejects 74% of the multi-site backgrounds (use 212Bi peak as conservative indicator) Original spectrum Scaled PSD result

  17. Detector type Rise-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 Previous Front-End Results 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

  18. Disasters Do Happen • We didn’t really like that FET anyway… Punishment for yielding 120 ns 10% - 90% performance

  19. Current LFEP Module Performance(2N4356 FET w/92cm leads) 40 ns 10-90% output pulse input power output power input pulse 25 MHz

  20. Background Goals Dominated by 232Th in Cu At this level, we might not get a count in a 3 year run!

  21. Cuts vs. Background Estimates

  22. Construction vs. Operations 68Ge build up and decay Ops Begins 80% of total 68Ge has decayed

  23. 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)

  24. 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)

  25. 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 R&D Module Construction Enriched Ge Module 1 Testing Module 2 Testing Module 3 Testing Operations Reference Schedule

  26. Majorana Sensitivity: Realistic runtime

  27. 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

  28. 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

  29. 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, OlegKochetov, 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

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