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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

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

the majorana 76 ge 0 nbb decay experiment

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
conceptual design of 57 crystal module

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)

shield design
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)
background goals and demonstrated levels
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
ge exposure timeline
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

granularity detector to detector rejection
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
pulse shape discrimination
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
time correlations
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

crystal segmentation

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
segmentation study experiment and simulation
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

ultra pure electroformed cu

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

design drivers analog performance needed for psd
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

multi parametric pulse shape discriminator
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

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

previous front end results

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

disasters do happen
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
Current LFEP Module Performance(2N4356 FET w/92cm leads)

40 ns 10-90%

output pulse

input power

output power

input pulse

25 MHz

background goals
Background Goals

Dominated by 232Th in Cu

At this level, we might not get a count in a 3 year run!

construction vs operations
Construction vs. Operations

68Ge build up and decay

Ops Begins

80% of total 68Ge has decayed

majorana sensitivity vs time
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)

a recent claim
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)

reference schedule

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
gerda relationship
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

majorana summary
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
slide29

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