Assay and Acquisition of Radiopure Materials

Priscilla Cushman University of Minnesota

LRT 2010, Sudbury Canada August 28-29

Principle InvestigatorsPriscilla Cushman (University of Minnesota)Dongming Mei (University of South Dakota)Kara Keeter (Black Hills State University) Richard Schnee (Syracuse University)

Assay and Acquisition of Radiopure Materials

• Characterize radon, neutron, gamma, and alpha/beta backgrounds at Homestake • Develop a conceptual design for a common, dedicated facility (FAARM) for low background counting and other assay techniques• Assist where appropriate in the creation of common infrastructure required to perform low background experiments.• Perform targeted R&D for ultra-sensitive screening and water shielding

Engineering ConsortiumCNA Consulting Engineers (Lee Petersen)Dunham Associates Miller Dunwiddie Architecture, Inc

An NSF S4 (~ $1M) was awarded for these specific tasks

Assay and Acquisition of Radiopure Materials

AARM is the Collaboration which includes members from many different experiments

AARM seeks to organize cross-experimental identification, assay, and storage of radiopure materials for shielding and construction of detectors and shared nuclear and materials database

Priority (S4) has been on designing the DUSEL FAARM = Facility for Assay and Acquisition of Radiopure Materials

Organization of early screening and integration of multiple sites is focusof our next collaboration meeting: November 12-13 @ Sanford Lab

LRT Discussion on same topic: Sunday at 4:20

Broader Collaboration – open enrollment !(http://zzz.physics.umn.edu/lowrad/collab) Scientific Collaboration

Craig AalsethHenning BackTim ClassenJodi CooleyDarren Grant

Yuri EfremenkoBrian FujikawaReyco HenningJeff MartoffRobert McTaggart

Esther MintzerAndreas PiepkeAndrew SonnensheinJohn Wilkerson Tullis Onstott

International Scientific Advisory PanelLaura Baudis (Zurich University)Richard Ford (Queen’s University, SNOLab)Gilles Gerbier (CEA Saclay)Gerd Heusser (Max Planck Institute, Heidelberg) Andrea Giuliani (University of Insubria (Como), Coordinator of ILIAS Continuation)Mikael Hult (European Commission: JRC Inst. for Reference materials and Measurements)Vitaly Kudryavtsev (University of Sheffield)Pia Loaiza (Laboratoire Souterrain de Modane)Matthias Laubenstein (INFN, Gran Sasso Laboratory)Neil Spooner (University of Sheffield)

Design and Location of FAARM

Design Principles

Surface/Shallow Infrastructure• Easy access for less sensitive screening

E&O projects, NAA HPGe, radiochemistry lab• New labs as needed (not in our “plan” – we will send samples out)

ICPMS, surface characterization, atom trace analysisDepends on the infrastructure in the surface campus

4850-ft level FAARM• deep enough for ultra sensitive screening and dark matter prototype testing• close to experiments for easy access (drive in large items) • share water purification and cryogen infrastructure• unite functions under a dedicated staff• Need new approach to multi-user shielding:

individual lead shields too expensive and not radiopureneutron shielding required for DM prototypes and Immersion tankmuon capture, activation, a-n/fission become important

Elements of FAARM

Entire facility is class 10,000 clean room, < 20 Bq/m3

Several class 1000 clean roomsAteko (NEMO facility provided 0.01 Bq/m3 breathable air at 150 m3/h)Radon-mitigated zones (<1 Bq/m3) and assembly areas (<0.1 Bq/m3)Radon-free storage and unified LN system Wet benches, clean machining, hoods, etc

Instrumented Water Shield with toroidal interior acrylic room

Houses ultra-sensitive screeners (GeMPI style, BetaCages) Reduce cost of individual lead shielding ($2M savings)Active Muon veto, Neutron & Gamma shieldingOuter shield of Immersion Tank, Space for Experiments & R&D Prototypes

Top-loading Immersion TankModeled on the Borexino CTF Whole body counting with 0.1 counts/day, E > 250 keVU/Th at .01/.04 ppt, surface at < 1 count/m2/day (unsealed)6 x 10-6 cts/kg/keV/day from Compton continuumOPTION: Could be replaced by highly segmented germanium

Elements of FAARM

Served by a trained technical staff

Develop staff in the Early Screening Program (DULBCF)Scheduling tools to optimize efficient use of screenersIntegrate with worldwide screeningIn-house analysis tools and databaseTransition the screening in a phased manner

Less sensitive screeners benefit from common facility

outside shield but inside clean area

Radon emanation, XIA alpha screeners, conventional HPGe

Areas for bio/geo/physics assembly

Intellectual center for a new field of low background studies

FAARM Elevation

FAARM First Floor

FAARM Second Floor

FAARM Rendering

FAARM Rendering

FAARM Rendering

Water Shield Simulations

Optimize shield thickness

Rock (Homestake 4850’)238U 0.55 ppm 232Th 0.3 ppm 40K 2.21%

Attenuation through Water + Stainless Steel

X

radiogenic neutronscosmogenic neutrons

(tagged)

Cavern radioactivityafter 2.3 m thick wall

7.974×10-5 /cm2/sn 4.817×10-10 /cm2/s

Contam Stainless Steel Acrylic

238U 0.1 ppb 9.5x10-6 24 ppt

232Th 0.1 ppb 2.3x10-6 14 ppt

40K 0.028 ppb 1.2x10-6 2.4x10-4 ppb

60Co 4.6x10-10 ppb 6.4x10-5

Total: 7.7x10-5 Total: ~10-5

vs

gamma’s from rock

Detailed Geant4 studies will determine

background levels

design optimization

materials choice support structures water purity PMT and QUPID placement active rejection light yield rejection efficiency

Upgrade options: Gd-loading or LS shield

A. Villano (Minnesota)

• 4 tonnes of scintillator (PC + 1.5 g/L PPO)

• 1m radius 500μm Nylon vessel for scintillator

• 2 m radius “shroud” vessel to shield Rn

• 3.6 p.e./PMT for 1 MeV electron

• Muon veto PMTs on floor

• 100 PMTs (Optical coverage: 21%)

• Buffer of water – 2.3m vessel to PMT

• Energy saturation: 6 MeV

Borexino Counting Test Facility

CTF-like Immersion Tank for Screening

Water shield becomes outer shroud and vetoLow radioactivity QUPIDs can be placed closer to LS Bigger 2 m diam. nylon bag filled with LAB Liq. Scint.Established purification methods (10-16 g/g U/Th andd 10-14 g/g K)

• Distillation (also removes Rn)• Water extraction• N2 stripping• Solid-column adsorption

Sensitive to • bulk gammas • betas and alphas from surface• betas inside 50 m nylon sample bag

Moderate energy resolution & Efficiency

Distinguish • via event reconstruction• via pulse shape

50%

Schedule for FAARMProcurement and Assembly

Before Module is ready, but money is allocated

• Detailed engineering-level design • Obtain bids, contracts and permits and hire contractor• Assemble and test water purification system• Procure radon system from Ateko (year lead time)• Choose photodetectors, screening and testing, bids• Purchase photodetectors, calibration and QA, electronics• Procure nylon and build dedicated clean room• Build nylon vessel in clean room

Once module is ready (Jan 2017) and radon < 100 Bq/m3 (ventilation, rock coating)

• Install Ateko in module, operate temporary radon-free room for sensitive materials• Water tank assembly incl torus + civil + radon under direction of contractor• Ateko moved to final location inside FAARM• Beneficial occupancy one year later.

Schedule for FAARMInstallation and Commissioning

After Beneficial Occupancy

Establish moderate cleanliness protocols immediately after heavy constructionClean entire lab as soon as possibleClean and coat interior of shield, Install cables, plumbing, air, cryogen systemInitial water fill and test plumbing – drain and cleanInstall Water Shield PMTs – fill shield, operate and calibrate PMTsComission DAQ and shield – long muon run - drain

Establish tight cleanliness protocol, including showers and radon mitigationMeasure particulate level and radon to confirm – commission monitoringAt least one sensitive HPGe moved to FAARM as bkgd monitor Install nylon vessel and QUPIDs (test and calibrate)Fill Immersion Tank with LSInstall nitrogen blanket, clean room – Purity studies with QUIPIDsFill shield – Combined Water + LS test and bkgd runMove other screeners in parallel with Immersion Tank commissioning

FAARM Installation & Commissioning

Created a Resource-loaded Cost & Schedule in Project.

MREFC $$ Jan ‘14

DUSEL readyJan ‘17

Civil FinishedJan ‘18

Start of schedule

Big Gap: 2010 – 2018

Need a Rational Plan until 2018 and how to transition to FAARM

Sanford Lab does NOT have enough room in Davis, nor funds to purchase screeners

Utilize existing underground sites and screeners until FAARM is readyThen - move the most sensitive screeners into FAARM shield collect less sensitive screeners as needed under one roof.

Most important aspect of FAARM is the active SHIELD Shield transforms sensitive screeners into ultra-sensitiveCentral pool can house a 3rd generation screenerShield has been optimized for COST:

~ $200k per Screener + Shield for prototype experiments

Move from model of dedicated screeners to a centrally managed systemDetermine needs for next decadeBegin to build a coherent team and staffMore efficient scheduling and new shared purchase schemesFind new sources of funding: EPSCOR, Sanford, University infrastructure …

• All screeners already bought, tested, and in operation from Early Screening era• Screening must continue with as few interruptions as possible• Staff is already in charge of all screeners, regardless of location• Each sensitive screener is commissioned at FAARM before the next one dismantled• Decommissioning effort (FTE) is flat over the year long transition

MILESTONE

1/18 Beneficial Occupancy

7/18 First GeMPI operational (Background Monitor)10/18 First Beta cage is screening at FAARM

Interleaved transfer schedule continues through the year

1/19 All XIA alpha screening now at FAARM2/19 All GeMPIs, BetaCages now at FAARM *** Decommission Soudan LBCF3/19 All gamma screening at FAARM *** Release Davis cavern6/19 Whole body screening in Immersion Tank *** Fully operational FAARM

“Early Screening” to FAARM Transition

Transitioning of Screening from multiple sites to FAARM Commissioning (detail)