The Majorana Demonstrator An Overview - SNOLAB · 1 Office of Nuclear Physics The Majorana...

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Office of Nuclear Physics

The Majorana DemonstratorAn Overview

Chang-Hong Yu

Oak Ridge National Laboratory

For the Majorana Collaboration

23/05/12 Changn-Hong Yu, SNOLab Opening Workshop, May, 2012


Majorana – Searching for 0νββ 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 0νββ δεχαψ, ωιτη α γοαλ οφ

λεαδινγ το α ποσσιβλε φυτυρε τοννε−σχαλε

εξπεριµεντ.

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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 0νββ δεχαψ) ρεθυιρεδ βψ α τοννε−σχαλε εξπεριµεντ

Εσταβλιση φεασιβιλιτψ οφ µοδυλαρ αρραψ οφ Γε δετεχτορσ

Τεστ τηε Κλαπδοε−Κλεινγροτηαυσ χλαιµ

Σεαρχη φορ λοω−ενεργψ δαρκ µαττερ (λιγητ ΩΙΜΠσ)


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.

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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


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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.


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MJD – from raw material to detectors and experiment


76GeO2

Zone refineDet. Unit

Det. String

Cryostat

Cu E-forming

ShieldShield assembly

UG Lab

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76Ge Procurement and ProcessingProduced 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


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

76Ge Sample Tests: 70Ge: 0.016 (3) %

76Ge: 88 (1)%

Specifications:70Ge: ≤ 0.07 %76Ge: ≥ 86 %

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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.



• 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

76Ge Processing

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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


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Detector Unit


Reduced ID HV ring: MJ80-02-124

Long Hollow Hex Rod: MJ80-02-123

OPPI Insulator: MJ80-02-127

HV ring: MJ80-02-033

HV nut: MJ80-02-001

Hollow Hex Rod: MJ80-02-020

Cable Guide: MJ80-02-002

Crystal Insulator: MJ80-02-032

• PPC detectors have been produced by multiple vendors.

• FWHM <1 keV at 60 keV, < 4.0 keV at 2039 keV.

• natGe detectors in hand (33 UG).

• ORTEC selected to produce enriched detectors.

• Excellent projected yield.• Detector fabrication starts in

June 2012.• Low-mass, ultra-low

background front end electronics

~0.6 kg

~1.0 kg

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Detector String Assembly


• Detectors working in strings with full set of low-background components.

• All Cu parts e-formed UG• Clean plastics as insulators• Training a crew of experts

to assemble strings.

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Cryostat

Changn-Hong Yu, SNOLab Opening Workshop, May, 2012

Top Lid:

Bottom Lid

Cold Plate w/ Connectors

MJD string assembly

IR Shield:

Detector strings fitted into cryostats

Cryostat made from UG e-formed Cu

Cooling by Thermosyphon

Cryostat size: 35cmX35cm

23/05/12

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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.

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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 e-formed Cu.

~ 18 months of e-forming remain for cryo 1 & 2 parts, inner shield,



Shield Structure

22 Feb 2012

Inner Cu Shield: 5 cm e-formed

Outer Cu Shield: 5 cm clean commercial

Lead: 45 cm clean bricks

Radon Exclusion Box:

Poly shieldScintillating Acrylic Veto Panels:

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The Monolith


Cryostat Assembly

Lead Stack top plate:

Monolith Bearing Table:

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Shield structure: Monolith moving on HOVAIR into shield

Monolith:

Hovair Transport:

Poly Shield:

Overfloor: Guide Rails:

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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)


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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 e-forming at Ross Campus since spring of 2011.


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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.


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Majorana Demonstrator Implementation


* Same design as Cryostat 1 & 2, but fabricated using commercial Cu components

Implementation Commissioning Dates

Prototype Cryostat* (2 strings, natGe) December 2012

Cryostat 1 (3 strings enrGe & 4 strings natGe)

October 2013

Cryostat 2 (7 strings enrGe) August 2014

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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


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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


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