Office of Nuclear Physics
THE MAJORANA DEMONSTRATOR
AN OVERVIEW
Chang-Hong Yu
Oak Ridge National Laboratory
For the MAJORANA Collaboration
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
1
MAJORANA – Searching for 0nbb Decay
Using a mixed array of enriched and natural
Ge as both the source and the detectors,
MAJORANA Demonstrator is an experiment
searching for the 0nbb decay, with a goal of
leading to a possible future tonne-scale
experiment.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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MAJORANA DEMONSTRATOR GOALS
• Demonstrate an achievable background rate of 1
count/tonne/year in the 4 keV ROI at 2039 keV (76Ge 0nbb
decay) required by a tonne-scale experiment
• Establish feasibility of modular array of Ge detectors
• Test the Klapdoe-Kleingrothaus claim
• Search for low-energy dark matter (light WIMPs)
To achieve background ~100 times lower than previous
Ge experiments, MAJORANA strives to
• Minimize the mass of construction materials
• Aggressive reduction of radioactive impurities in
materials
• Minimize the exposure to cosmic rays.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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Majorana Organization and Funding
• ~100 collaborators from ~25 institutions
• ORNL is the lead Laboratory
• Total project funding by U.S. Dept. of Energy and
National Science Foundation: ~$24 million.
• Additional contributions from collaborating
institutions.
• Additional DOE and NSF program re-direct
efforts
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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MAJORANA Demonstrator Scope
• Background Goal in the 0νββ peak region of interest (4 keV at
2039 keV) 3 counts/ROI/t/y (after analysis cuts)
– scales to 1 count/ROI/t/y for a tonne experiment
• 40-kg of Ge detectors – 30-kg of 86% enriched 76Ge crystals &
10-kg of natGe
– Detector Technology: P-type, point-contact (PPC) detectors.
• 2 independent cryostats
– ultra-clean, electroformed Cu
– 20 kg of detectors per cryostat
– naturally scalable
• Compact Shield
– low-background passive Cu and Pb shield with active muon veto
• Aim to collect 100 kg-years of enrGe data to demonstrate
background.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
6
MJD – from raw material to detectors
and experiment
76GeO
2
Zone refine
Det. Unit
Det. String
Cryostat
Cu E-forming
Shield
Shield assembly
UG Lab
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
7
76Ge
Procurement and Processing
• Produced by ECP in Russia
• Total procurement: 40 kg 76Ge enriched to 86% or higher.
– 1st 20 kg arrived in Oak Ridge in Sep. 2011.
– 2nd 20 kg to arrive in Aug. 2012
• Additional 5-10 kg contribution from Russian collaborators
76Ge
Steel shielding container
•
•
•
Weight: 15 tons. Outer : ∅140 cm х 126.5 сm
(H), Cavity: ∅54 сm х 40 сm (H).
Suppression of activation in 76Ge: factors for
68Ge and 60Co are 10 and 15, respectively.
Effective irradiation time: 15% of real
transportation time
6/30/2016
Changn-Hong Yu,
Sample Tests:
70Ge: 0.016 (3) %
76Ge:
88 (1)%
Specifications:
70Ge: ≤ 0.07 %
76Ge: ≥ 86 %
SNOLab Opening Workshop, May, 2012
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Underground Storage in Oak Ridge –
The Cherokee Caverns
• A natural cave that has sufficient
overburden (130 ft) of Dolomite
rocks to block cosmic rays (~ 80
m.w.e.). Measured muon
attenuation is a factor 15 vs.
surface.
• Easy access from Oak Ridge (<
15 min. drive)
• Cave has a large space and
adequate entrance passage for
storage.
• Security measures implemented to
assure material safety.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
9
76Ge
Processing
• Electrochemical Systems, Inc (ESI) in Oak Ridge is contracted by
MJD to process and zone refine 76Ge.
• ESI had no prior experience. Retired Ge processing experts were
hired to consult ESI.
• First results: 20 kg 76Ge reduced and zone-refined in 3 months time.
19.5 kg detector grade metal ready to be delivered
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
10
Detector Design
• Several detector types were evaluated: standard coaxial (p- and
n-type), segmented coaxial, and p-type PPC.
• PPC was chosen for its exceptional resolution, low threshold,
and powerful multi-site rejection via PSD (as good as highly
segmented coaxial detector).
• Many PPC prototype detectors operating successfully
• Detector mass: 0.6-1 kg
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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Detector Unit
•
PPC detectors have been
produced
by multiple vendors.
HV ring:
MJ80-02•033 FWHM <1 keV at 60 keV, <
HV nut: MJ80-02-001
4.0 keV at 2039 keV.
natGe detectors in hand (33
• Hollow
Hex Rod: MJ80-02-020
UG).
Insulator:
MJ80-02-032
• Crystal
ORTEC
selected
to produce
enriched detectors.
Cable Guide: MJ80-02-002
• Excellent projected yield.
• Detector fabrication starts in
Reduced
ID HV
ring: MJ80-02June
2012.
124
• Hollow
Low-mass,
Long
Hex Rod:ultra-low
MJ80-02background front end
123
OPPI Insulator: MJ80-02-127
electronics
~0.6 kg
~1.0 kg
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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Detector String Assembly
•
•
•
•
6/30/2016
Changn-Hong Yu,
Detectors working in
strings with full set of lowbackground components.
All Cu parts e-formed UG
Clean plastics as insulators
Training a crew of experts
to assemble strings.
SNOLab Opening Workshop, May, 2012
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Cryostat
Top Lid:
Cold Plate w/
Connectors
• Detector
strings fitted
into cryostats
MJD string
assembly
• Cryostat made
from UG eformed Cu
IR Shield:
• Cooling by
Thermosypho
n
Bottom Lid
• Cryostat size:
35cmX35cm
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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Status of Cryostat & Vacuum System
• Prototype cryostat
being fabricated
• Thermosyphon is
fabricated and tested.
• Prototype vacuum
system designed,
reviewed, assembled,
is being tested.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
15
Electroformed Cu for ultra-low background
• Electroformed Cu will be used for detector parts, cryostat & inner 5 cm
of passive shield.
• Start with the cleanest stock copper available and electroform
underground -- orders-of-magnitude lower background compared to
commercial Cu.
• 16 baths working: 10 at SURF (4850L), 6 at PNNL shallow UG lab
• Mandrels pulled from baths at PNNL and TCR. Cu machined, removed,
and flattened. Properties look good. Small parts fabricated from eformed Cu.
• ~ 18 months of e-forming remain for cryo 1 & 2 parts, inner shield,
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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Shield Structure
Scintillating Acrylic
Veto Panels:
Radon Exclusion
Box:
Poly shield
Lead: 45 cm clean bricks
Inner Cu Shield:
5 cm e-formed
Outer Cu Shield: 5 cm
clean commercial
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Feb 2012
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
17
The Monolith
Lead Stack top plate:
Cryostat Assembly
Monolith Bearing Table:
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Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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Shield structure: Monolith moving on HOVAIR
into shield
Poly Shield:
Monolith:
Overfloor:
Guide Rails:
Hovair
Transport:
19
MJD Engineering Design Status
• Conceptual Design & Review – Complete
Summer 2010
• Preliminary Design & Review – Complete Feb
2011
• Final Design & Review:
– Prototype cryostat - 95% (250 engineering drawings
released, 90% fabricated);
– Cryostat 1 & 2 - design is essentially the same as
prototype cryostat
– Shield - 80% (100 released)
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
20
Underground Lab
• Sanford Underground Research Facility (SURF) at Homestake
in SD,
• Main Lab at 4850 level Davis Campus.
• Operating Temporary Clean Room (TCR) at 4850L for eforming at Ross Campus since spring of 2011.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
21
Current Status at SURF
• Temporary Clean Room at Ross Campus
operational since April 2011.
• MJD Davis Lab at SURF: Davis Campus
outfitting nearly complete. Initial MJD occupancy
in April. Clean operations in June 2012
• Above ground machine shop (AGMS)
implemented January 2012, operational since
Feb. 2012.
• Major procurements - all issued, most received.
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
22
MAJORANA Demonstrator Implementation
Implementation
Commissioning
Dates
Prototype Cryostat* (2 strings, natGe)
Cryostat 1 (3 strings enrGe & 4 strings natGe)
Cryostat 2 (7 strings enrGe)
December 2012
October 2013
August 2014
* Same design as Cryostat 1 & 2, but fabricated
using commercial Cu components
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
23
Future Tonne-Scale Ge Experiment
• Utilizes and builds on major R&D activities related to
GERDA and MAJORANA Collaborations.
• Pursuing a range of shield designs between the compact
and the GERDA like. Ultimate design will be based on
results from GERDA Phases I & II and the MAJORANA
DEMONSTRATOR.
• Preliminary info should be available in 2014 from both
GERDA Phase II and MJD Cryo 1. Aim to reach
agreement on the down select process during FY14.
• Potential UG site options:
– SNOLAB 6800L
– China Jinping Underground Laboratory (中国锦屏地下
实验室）8240L
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
24
Summary
• MJD design based on 30 kg enrGe + 10 natGe option
complete and on budget.
• Backgrounds projected to meet cleanliness goals
• E-formed Cu being produced UG at SURF TCR & PNNL
• Cryostat final design complete. Fabrication and assembly
underway on prototype cryostat.
• Final shield design nearing completion. Initial UG
assembly starts in June, 2012.
• Successful reduction and refinement of first 20kg of enrGe
with 97.46% yield.
• Contract with the detector vendor is being awarded now
with favorable schedule and cost.
• Projected commissioning schedule:
– prototype cryostat – Dec. 2012
– cryostat 1 – Oct. 2013
– cryostat 2 – Aug. 2014
6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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6/30/2016
Changn-Hong Yu,
SNOLab Opening Workshop, May, 2012
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