INPAC Meeting, Berkeley May 5, 2007 Majorana Status and Perspectives1 Kai Vetter Lawrence Livermore...
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Transcript of INPAC Meeting, Berkeley May 5, 2007 Majorana Status and Perspectives1 Kai Vetter Lawrence Livermore...
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 1
Majorana Status and Perspectives
Kai VetterLawrence Livermore National Laboratory
UC Berkeley
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 2
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, California and
the University of California - BerkeleyYuen-Dat Chan, Mario Cromaz, Brian Fujikawa,,
Donna Hurley, Kevin Lesko, Paul Luke, Akbar Mokhtarani,Alan Poon, Gersende Prior, Nikolai Tolich, Craig Tull
Lawrence Livermore National Laboratory, Livermore, CaliforniaDave Campbell, Kai Vetter
Los Alamos National Laboratory, Los Alamos, New MexicoSteven 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
Oak Ridge National Laboratory, Oak Ridge, TennesseeCyrus Baktash, Jim Beene, Fred Bertrand, Thomas V. Cianciolo,
David Radford, Krzysztof Rykaczewski, Chang-Hong Yu
Osaka University, Osaka, JapanHiroyasu Ejiri, Ryuta Hazama, Masaharu Nomachi, Shima
Tatsuji
Pacific Northwest National Laboratory, Richland, WashingtonCraig 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
Queen's University, Kingston, OntarioFraser 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 CarolinaHenning Back, James Esterline, Reyco Henning,
Mary Kidd, Werner Tornow, Albert Young
University of Chicago, Chicago, IllinoisPhil Barbeau, Juan Collar, Keith Crum, Smritri Mishra,
Brian Odom, Nathan Riley
University of South Carolina, Columbia, South CarolinaFrank Avignone, Richard Creswick, Horatio
A. Farach, Todd Hossbach, George King
University of South Dakolta, Vermillion, South DakotaTina Keller, Dongming Mei
University of Tennessee, Knoxville, TennesseeWilliam Bugg, Tom Handler, Yuri Efremenko, Brandon White
University of Washington, Seattle, WashingtonJohn 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
The Majorana Collaboration
Note: Red text indicates students
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 3
Neutrinoless Double Beta Decay
• Immediate Implications of Discovery:– Neutrino is Majorana (own antiparticle)– Total Lepton Number is not conserved– Neutrino has mass (known)
• Well-studied example: Exchange of virtual neutrino.
• Could probe absolute Mass-scale of Neutrino:
ZA Z2A 2e
T1/ 20 1
(Matrix Element) (Phase Space) m
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 4
Decay Sensitivity to <m>
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 5
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 0 peak
region-of-interest (ROI) (1 count/t-y)
• High Q value• Best possible energy
resolution– Minimize 0 peak ROI
to maximize S/B– Separate 2/0
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 6
Experimental Program in Search
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 7
Ge Detection Principle
• Majorana uses 76Ge
• Enriched HPGe Diodes -- Detector is Source.
• Excess at Q = 2039 keV
• Demonstrated in IGEX, Heidelberg Moscow.
• Intrinsically clean
electrons
holes
Ionizing radiation interaction site
n
p
HPGe Detectors have excellent energy resolution
0.16% at ROI for Majorana
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 8
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 y0.24 < 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
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 9
76Ge Sensitivity & Background Dependence
T1/2 ln(2) ff atoms time
decays
1
m 2T1/2
ln(2) ff atoms time
Bi (t)dtLimiting case of no obs. decays
<m> of
100 meV[Rod06]
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 10
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.
– -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
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 11
The Majorana Modular Approach1 Concept: 57 crystal modules
– Conventional vacuum cryostat made with electroformed Cu.– Scalable to 1-tonne
Cold Plate
Crystal
ThermalShroud
Vacuum jacket
Cold Finger
Bottom Closure 1 of 19 crystal stacks
CapCap
Tube (0.007” wall)
Tube (0.007” wall)
Ge(62mm x 70 mm)
Ge(62mm x 70 mm)
Tray(Plastic, Si, etc)
Tray(Plastic, Si, etc)
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 12
– Ultra-radiopure materials– Deep underground: >5000’– Modular deployment.– 40 cm bulk Pb, 10 cm ultra-
low background shield– Active 4 veto detector
Materials and Shielding
Top view
57 Detector Module
Veto Shield
Sliding Monolith
LN Dewar
Inner Shield
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 13
Concepts for background suppression
60Co
(“Low” Energy)
(“High” Energy)
(“High” Energy)
Pulse-shape discrimination
Segmentation
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 14
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
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 15
Highly Segmented N-Type Detectors
• Approach: Highly 2-D segmented n-type 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 0 event - 1 to 2 mm)
– Significant R&D effort completed (GRETINA, AGATA, LLNL Compton imager)
– Direct connection to NP projects
• Drawback:– Slower detector production rate– Most additional components (contacts, readout)– Most complicated acceptance, characterization,
and assembly– Requires design modifications (electronics,
mechanically)
6x6 9-detector module
60Co suppression w/ 32-fold segmented MSU detector”Red: single segmentBlue: with PSA
Suppression by segmentation and 3D PSA
Measured with 40-fold segmented LLNL detector
Full 3D event reconstruction and Compton imaging with
LLNL detectorCompton image of 137Cs source
GRETA 4 detector module prototype LLNL
Coaxial Imager
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 16
Ge-drift/ modified electrode/ point contact detectorConventional, closed-ended coaxial detector
Modified electrode coaxial detector
Highly sensitive background suppression by PSA
• Approach: Non-segmented p-type HPGe 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 - contamination
• Drawback:– Only one detector fabricated– Production rate, sensitivity to Ge material
requirements (e.g. impurity concentration) uncertain.– No 3D reconstruction possible
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 17
Counts per Region of interest per Ton-Year
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
Unsegmented p-type Modified electrode n-type 2x3 n-type 6x6 3D
SurfacesExternal
Small partsPb
Cu OuterCu ShieldCryostat
Inner MountGe
Anticipated background rates
Background rates are comparable !Background suppression compensates the increased background
level for segmented and more complex implementations
Counts per Region of Interest per Ton-Year
Non-segmentedP-type
ModifiedElectrode
P-type
2x3 segmentedN-type
6x6 segmentedN-type
1.0
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 18
Majorana R&DTowards 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)
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 19
Majorana R&D Module
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 20
1-ton 76Ge Sensitivity vs. Background
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 21
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.
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 22
Opportunities for UC
• What does it take to build a 1-ton 76Ge experiment?– Fabrication challenges: Cost & schedule …– Do we have the best technology?
• Can we enlarge our vision: 76Ge -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
INPAC Meeting, BerkeleyMay 5, 2007
Majorana Status and Perspectives 23
Majorana & GERDA