Majorana Status and Overview
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Majorana Status and Perspectives Kai Vetter Lawrence Livermore National Laboratory UC Berkeley Majorana Status and Perspectives 1 INPAC Meeting, Berkeley May 5, 2007 The Majorana Collaboration Institute for Theoretical and Experimental Physics, Moscow, Russia Pacific Northwest National Laboratory, Richland, Washington Alexander Barabash, Sergey Konovalov, Igor Vanushin, Vladimir Yumatov Craig Aalseth, James Ely, Tom Farmer, Jim Fast, Eric Hoppe, Brian Hyronimus, David Jordan, Jeremy Kephart, Richard T. Kouzes, Harry Miley, John Orrell, Jim Reeves, Robert Runkle, Bob Schenter, John Smart, Bob Thompson, Ray Warner, Glen Warren 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 Queen's University, Kingston, Ontario Fraser Duncan, Aksel Hallin, Art McDonald Triangle Universities Nuclear Laboratory, Durham, North Carolina and Physics Departments at Duke University ,North Carolina State University, and the University of North Carolina Lawrence Berkeley National Laboratory, Berkeley, California and the University of California - Berkeley Yuen-Dat Chan, Mario Cromaz, Brian Fujikawa,, Donna Hurley, Kevin Lesko, Paul Luke, Akbar Mokhtarani, Alan Poon, Gersende Prior, Nikolai Tolich, Craig Tull Henning Back, James Esterline, Reyco Henning, Mary Kidd, Werner Tornow, Albert Young University of Chicago, Chicago, Illinois Lawrence Livermore National Laboratory, Livermore, California Dave Campbell, Kai Vetter Phil Barbeau, Juan Collar, Keith Crum, Smritri Mishra, Brian Odom, Nathan Riley Los Alamos National Laboratory, Los Alamos, New Mexico University of South Carolina, Columbia, South Carolina Steven Elliott, Gerry Garvey, Victor M. Gehman, Vincente Guiseppe, Andrew Hime, Bill Louis, Geoffrey Mills, Kieth Rielage, Larry Rodriguez, Richard Schirato, Laura Stonehill, Richard Van de Water, Hywel White, Jan Wouters Frank Avignone, Richard Creswick, Horatio A. Farach, Todd Hossbach, George King University of South Dakolta, Vermillion, South Dakota Tina Keller, Dongming Mei Oak Ridge National Laboratory, Oak Ridge, Tennessee University of Tennessee, Knoxville, Tennessee Cyrus Baktash, Jim Beene, Fred Bertrand, Thomas V. Cianciolo, David Radford, Krzysztof Rykaczewski, Chang-Hong Yu William Bugg, Tom Handler, Yuri Efremenko, Brandon White University of Washington, Seattle, Washington Osaka University, Osaka, Japan John Amsbaugh, Tom Burritt, Jason Detwiler, Peter J. Doe, Alejandro Garcia, Mark Howe, Rob Johnson, Michael Marino, Sean McGee,R. G. Hamish Robertson, Alexis Schubert, Brent VanDevender, John F. Wilkerson Hiroyasu Ejiri, Ryuta Hazama, Masaharu Nomachi, Shima Tatsuji Note: Red text indicates students Majorana Status and Perspectives 2 INPAC Meeting, Berkeley May 5, 2007 Neutrinoless Double Beta Decay • Immediate Implications of Discovery: – Neutrino is Majorana (own antiparticle) – Total Lepton Number is not conserved – Neutrino has mass (known) • • Z A A 2e Z 2 Well-studied example: Exchange of virtual neutrino. Could probe absolute Mass-scale of Neutrino: T 0 1 1/ 2 (Matrix Element) (Phase Space) m Majorana Status and Perspectives 3 INPAC Meeting, Berkeley May 5, 2007 0bb Decay Sensitivity to <mbb> Majorana Status and Perspectives 4 INPAC Meeting, Berkeley May 5, 2007 Experimental Considerations • Measure extremely rare decay rates : T1/2 ~ 1026 -1027 years (~1013x age of universe!) • • Large, highly efficient source mass. Extremely low (near-zero) backgrounds in the 0bb peak region-of-interest (ROI) (1 count/t-y) 1. 2. High Q value Best possible energy resolution – – Minimize 0bb peak ROI to maximize S/B Separate 2bb/0bb Majorana Status and Perspectives 5 INPAC Meeting, Berkeley May 5, 2007 Experimental Program in 0bb Search Majorana Status and Perspectives 6 INPAC Meeting, Berkeley May 5, 2007 Ge Detection Principle • Majorana uses 76Ge n • Enriched HPGe Diodes -Detector is Source. electrons • Excess at Q = 2039 keV p Ionizing radiation interaction site • Demonstrated in IGEX, Heidelberg Moscow. • Intrinsically clean holes HPGe Detectors have excellent energy resolution 0.16% at ROI for Majorana Majorana Status and Perspectives 7 INPAC Meeting, Berkeley May 5, 2007 We don’t want to repeat that … • The Klapdor-Kleingrothaus Result Klapdor-Kleingrothaus H V, Krivosheina I V, Dietz A and Chkvorets O, Phys. Lett. B 586 198 (2004). Best result - 5 76Ge crystals, 10.96 kg of mass, 71 kg-years of data. 1/2 = (1.19 +2.99/-0.5 ) x 1025 y 0.24 < mv < 0.58 eV (3 ) Plotted a subset of the data for four of five crystals, 51.4 kg-years of data. 1/2 = (1.25 +6.05/-0.57) x 1025 y • • • Pulse shape selected spectrum (single site events) Much smaller background More (efficient) tools to identify and suppress background Better systematic handles on data Majorana Status and Perspectives 8 INPAC Meeting, Berkeley May 5, 2007 76Ge Sensitivity & Background Dependence T1/2 ln(2) ff atoms time 1 decays m 2 Limiting ln(2) ff atoms time T 1/2 case of no Bi (t) dt obs. decays <m> of 100 meV [Rod06] Majorana Status and Perspectives 9 INPAC Meeting, Berkeley May 5, 2007 Background Identification • Majorana is background limited. • Goal: 1 event / ton-year in 4 keV ROI • Backgrounds: – Natural isotope chains: 232Th, 235U, 238U, Rn – Cosmic Rays: • Activation at surface creates 68Ge, 60Co. • Hard neutrons from cosmic rays in rock and shield. – 2bb-decays. • Need factor ~100 reduction over what has been demonstrated. • Monte Carlo estimates of acceptable levels • Most backgrounds are multi-site. Signal is single-site Majorana Status and Perspectives 10 INPAC Meeting, Berkeley May 5, 2007 The Majorana Modular Approach 1 Concept: 57 crystal modules – Conventional vacuum cryostat made with electroformed Cu. – Scalable to 1-tonne Vacuum jacket Cap Cold Plate Tube (0.007” wall) Cold Finger Ge (62mm x 70 mm) Crystal Tray (Plastic, Si, etc) Thermal Shroud Bottom Closure Majorana Status and Perspectives 1 of 19 crystal stacks 11 INPAC Meeting, Berkeley May 5, 2007 Materials and Shielding – – – – Ultra-radiopure materials Deep underground: >5000’ Modular deployment. 40 cm bulk Pb, 10 cm ultralow background shield – Active 4 veto detector Top view Veto Shield Sliding Monolith LN Dewar Inner Shield 57 Detector Module Majorana Status and Perspectives 12 INPAC Meeting, Berkeley May 5, 2007 Concepts for background suppression Segmentation Pulse-shape discrimination 0bb g(“High” Energy) 0bb g(“High” Energy) g 60Co g g(“Low” Energy) Majorana Status and Perspectives 13 INPAC Meeting, Berkeley May 5, 2007 Advanced Concepts in Detector and Data Processing Technologies • Ge-drift/ modified electrode/ point contact detector • Highly segmented coaxial HPGe detectors – N-type (e.g. GRETA, LLNL Coaxial Imager) – P-type (?) • Low mass/ high resolution FE electronics (FET, preamplifiers) • Digital acquisition and processing system – 1D-3D signal and data processing Majorana Status and Perspectives 14 INPAC Meeting, Berkeley May 5, 2007 Highly Segmented N-Type Detectors • Approach: Highly 2-D segmented n-type 6x6 9-detector module HPGe detector with 3D PSA of segments • Advantage: – Best background rejection – Best event characterization in 3D with interaction separation and gamma-ray reconstruction (w/ accuracy of the size of 0bb event - 1 to 2 mm) – Significant R&D effort completed (GRETINA, AGATA, LLNL Compton imager) – Direct connection to NP projects Suppression by segmentation and 3D PSA • Drawback: 60Co suppression w/ 32fold segmented MSU detector” Red: single segment Blue: with PSA – Slower detector production rate – Most additional components (contacts, readout) – Most complicated acceptance, characterization, and assembly – Requires design modifications (electronics, mechanically) LLNL Coaxial Imager Measured with 40-fold segmented LLNL detector q GRETA 4 detector module prototype Full 3D event reconstruction and Compton imaging with LLNL detector Majorana Status and Perspectives 15 Compton image of 137Cs source f INPAC Meeting, Berkeley May 5, 2007 Ge-drift/ modified electrode/ point contact detector Conventional, closedended coaxial detector • Approach: Non-segmented p-type HPGe Modified electrode coaxial detector detectors employing pulse-shape analysis in modified electrode or Ge-drift configuration • Advantage: – High background rejection due to PSA sensitivity – Low energy threshold (~300 eV) – P-type material for potentially high fabrication rate and low cost – Minimum number of readout components – Simple configuration in terms of design, production, and operation of cryostat, mounts, readout, and cooling. – Easy acceptance, characterization, and assembly. – “Thick” outside contact attenuating potential surface a - contamination Highly sensitive background suppression by PSA • Drawback: – Only one detector fabricated – Production rate, sensitivity to Ge material requirements (e.g. impurity concentration) uncertain. – No 3D reconstruction possible Majorana Status and Perspectives 16 INPAC Meeting, Berkeley May 5, 2007 Anticipated background rates Counts per Region of interest per Ton-Year Counts per Region of Interest per Ton-Year 1.80 1.60 Non-segmented P-type Modified Electrode P-type 2x3 segmented N-type 6x6 segmented N-type 1.40 1.20 Surfaces External Small parts Pb Cu Outer Cu Shield Cryostat Inner Mount Ge 1.01.00 0.80 0.60 0.40 0.20 0.00 Unsegmented p-type Modified electrode n-type 2x3 n-type 6x6 3D Background rates are comparable ! Background suppression compensates the increased background level for segmented and more complex implementations Majorana Status and Perspectives 17 INPAC Meeting, Berkeley May 5, 2007 Majorana R&D Towards a 1-ton experiment • Phase I: Construct 30-60 kg R&D Module • Mixed detectors, enrichment levels • Goals: – Selection of optimal detector design: • Highly/modestly segmented • Modified electrode • Unsegmented p-type – Verification of background simulation. – Materials, in particular cable and copper shielding. • Continued cooperation with GERDA collaboration (MaGe, materials, Liquid Ar Shield) Majorana Status and Perspectives 18 INPAC Meeting, Berkeley May 5, 2007 Majorana R&D Module Majorana Status and Perspectives 19 INPAC Meeting, Berkeley May 5, 2007 1-ton 76Ge Sensitivity vs. Background Majorana Status and Perspectives 20 INPAC Meeting, Berkeley May 5, 2007 Schedule • Submit R&D proposal this summer for demonstration prototype for 1-ton. • Construction in FY09. • Collect data FY11. 30-60 kg. of enriched material. Majorana Status and Perspectives 21 INPAC Meeting, Berkeley May 5, 2007 Opportunities for UC • What does it take to build a 1-ton 0bb 76Ge experiment? – Fabrication challenges: Cost & schedule … – Do we have the best technology? • Can we enlarge our vision: 76Ge 0bb-in general fundamental physics – Instrumentation as common link? – Institute for NPAC Instrumentation? Center of Excellence? – Instrumentation technologies • Detector • Data processing – Material processing with emphasis on (radio) purity • Ties to – DUSEL – Homeland Security/ Nuclear Nonproliferation Majorana Status and Perspectives 22 INPAC Meeting, Berkeley May 5, 2007 Majorana & GERDA Majorana Status and Perspectives 23 INPAC Meeting, Berkeley May 5, 2007
