The Sanford Underground Research Facility at Homestake

5 MB·

by  J. Heise

The Sanford Underground Research Facility at Homestake
J. Heise
SanfordUndergroundResearchFacility,630EastSummitStreet,Lead,SD57754
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Abstract. The former Homestake gold mine in Lead, South Dakota is being transformed into a dedicated laboratory to
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pursueundergroundresearchinrare-processphysics,aswellasofferingresearchopportunitiesinotherdisciplinessuchas
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biology, geology and engineering. A key component of the Sanford Underground Research Facility (SURF) is the Davis

n Campus,whichisinoperationatthe4850-footlevel(4300m.w.e)andcurrentlyhoststhreeprojects:theLUXdarkmatter
a experiment,theMAJORANADEMONSTRATORneutrinolessdouble-betadecayexperimentandtheCUBEDlow-background
J counter. Plans for possible future experiments at SURF are well underway and include long baseline neutrino oscillation

5 experiments,futuredarkmatterexperimentsaswellasnuclearastrophysicsaccelerators.Facilityupgradestoaccommodate
someofthesefutureprojectshavealreadystarted.SURFisadedicatedfacilitywithsignificantexpansioncapability.

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Keywords: Undergroundlaboratory,darkmatter,neutrino,double-beta,nuclearastrophysics
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e PACS: 14.60.Pq,23.40.-s,26.00,95.35.+d
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n INTRODUCTION
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s Many disciplines benefit from access to an undergroundfacility dedicated to scientific research, including physics,
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i biology,geology,engineering,and a well-established science programis currently underwayat the Sanford Under-
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groundResearchFacility(SURF).TheuniqueundergroundenvironmentatSURFallowsresearcherstoexploreahost
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h of important questions regarding the origin of life and its diversity, mechanisms associated with earthquakesand a
p numberofengineeringtopics.Adeepundergroundlaboratoryisalsowheresomeofthemostfundamentaltopicsin
[ physicscanalsobeinvestigated,includingthenatureofdarkmatter,thepropertiesofneutrinosandthesynthesisof

atomicelementswithinstars.
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SURF is being developed in the former Homestake gold mine, in Lead, South Dakota [1, 2]. Barrick Gold
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1 Corporation donated the site to the State of South Dakota in 2006, following over 125 years of mining [3], during
6 whichtime over600km oftunnelsandshaftswere createdin the facility, extendingfromthe surface to over8,000
8 feetbelowground.TheLaboratorypropertycomprises186acresonthesurfaceand7,700acresunderground,andthe
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SurfaceCampusincludesapproximately253,000grosssquarefeetofexistingstructures.TheSouthDakotaScience
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1 and TechnologyAuthority (SDSTA) operates and maintainsthe SanfordLaboratoryat the Homestake site in Lead,
0 SouthDakotawithmanagementoversightbyLawrenceBerkeleyNationalLaboratory(LBNL).
4 In 2006,SouthDakota philanthropist,T. DennySanford,gifted $70Mto convertthe formermine into a research
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laboratoryanddevelopascienceeducationfacility.WiththesefundsandastrongcommitmentfromtheStateofSouth
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v Dakota(appropriationsof$42.2Mtodate),safeaccesstotheundergroundhasbeenreestablished.
i TheinitialconceptsforSURFweredevelopedwiththesupportoftheUSNationalScienceFoundation(NSF)asthe
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primarysitefortheNSF’sDeepUndergroundScienceandEngineeringLaboratory(DUSEL)[4].WiththeNational
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a ScienceBoard’sdecisiontohaltdevelopmentofaNSF-fundedundergroundlaboratory,theUSDepartmentofEnergy
(DOE)nowsupportsthemajorityoftheoperationofthefacility.SupportforexperimentsatSURFcomesfromboth
the NSF and DOE as well as other agencies such as the USGS and NASA. Elements of the Homestake DUSEL
PreliminaryDesignReport[5]continuetobeusefulasthefeasibilityforportionsoftheoriginalplanareinvestigated.
FACILITYOPERATIONSINFRASTRUCTURE
Maintenanceandoperationofkeyelementsoffacilityinfrastructureenablessafeaccessunderground.Transportation
ofpersonnelandmaterialsundergroundis accomplishedusingthe two primaryshafts,the RossShaftandtheYates
Shaft.PairsofhoistsnearboththeRossandYatesshaftsmovepersonnelandrockconveyancesthroughtherespective
shafts. Pumpingstations in the Ross Shaftallow groundwater to be pumpedto surface.Undergroundventilationis
FIGURE1. ThelongsectionoftheformerHomestakeGoldMine.Thisfigureillustratesthe60undergroundlevelsextendingto
greaterthan8,000feetbelowground.ThelocationofcrosssectionisindicatedintheinsetalongaNWtoSEplane.Theprojection
extendsfor5.2kmalongthisplane.
providedby the Oro Hondo fan as well as the fan at #5 Shaft, which bring fresh air undergroundvia the Ross and
YatesShafts.
A key feature of the SanfordLaboratoryis the capacity for redundancy.Redundantpower,fiber optics cable and
ventilationarebroughtundergroundviatheRossandYatesShafts.Aswell,thetwoshaftsaswellasnumerousramp
systemsprovidemultipleoptionsforemergencyegress.
InitialrehabilitationofthesurfaceandundergroundinfrastructurefocusedontheRossshaftthatprovidesaccessto
themajorityofundergroundutilities,includingthepumpingsystemusedtoremovewaterfromthemine.Contractor
workintheRossshaftstartedJuly2008andwascompletedbyOctober2008,afterwhichSDSTApersonnelcontinued
withmaintenanceandrenovations,includingtheremovalofunusedlegacypiping(12km)andpower/communication
cables(2km).StartedinNovember2008,theYatesshaftrenovationwascompletedinMay2012withtheinstallation
ofanewpersonnelconveyanceandemergencybrakingsystem.TheRossShaftprovidedprimaryundergroundaccess
fromthestartofre-entryin2007untiltheYatesshaftwasreadyinMay2012.Personnelandmaterialsaretransported
undergroundmainly using the Yates cage, which has dimensions 1.4 m wide × 2.7 m tall × 3.8 m long and has a
maximum load capacity of 10,000 lbs (4,536 kg). The Yates cage schedule accommodates three shifts per day for
sciencepersonnel,providing24-houraccessasneeded.
Theaveragegroundwaterinflowintotheundergroundworkingsisapproximately730gpm.Afterpumpingceased
inJune2003[6,7],theminefilledwithwateruntilahigh-watermarkof1381meters(4530feet)belowsurfacewas
reachedinAugust2008.SustainedpumpingresumedinJune2008,droppingthewaterlevelbelowthe4850Levelby
May2009.SinceApril2012thewaterlevelisbeingmaintainedaroundthe6000-footlevelbelowsurface.Whilethe
potentialfor accommodatingdeeperaccess exists, withouta fundedmandateto developlaboratoryspace below the
4850-footlevel,thereisbenefitintermsofcostandsafetyformaintainingthewaterlevelaroundthecurrentlevel.
Adeep-wellpumpwasinstalledJuly2010andiscurrentlylocatedabout6424feetbelowsurfacein#6Winze,which
extendsfromthe4850Leveltothedeepestareasofthefacility.Permanentstationsemploying700-horsepowerpumps
are located on the 1250, 2450, 3650 and 5000 Levels in the Ross shaft. Water received at the surface Waste Water
Treatment Plant (WWTP) is combined with Homestake-Barrick water and treated to remove iron that has leached
fromthemineworkingsandtraceamountsofammonia.ThedischargecapacityfromtheWWTPisroughly2000gpm
usingbiologicalandsand-filtertechnologies.
Single-mode fiber optics cable is deployed throughout the facility and current network hardware provides inter-
campuscommunicationat100–1000Mbps.Redundantconnectionsexisttotheoutsideworld,includingcommodity
internet(“Internet1”)at1Gbpsandresearchinternet(“Internet2”viathestateResearch,EducationandEconomic
Development(REED)network)at1Gbps,whichcanbeexpandedto100Gbpswithappropriatehardwareupgrades.
Redundantfiberconnectionsconnectthesurfacetothe4850LviatheRossandYatesShafts,andworkinunderway
toensurethatthecorenetworkequipmentisprotectedbyuninterruptiblepowersuppliesandinmostcasesgenerator
power.
In order to provide increased capacity to support the construction and operation of future experiments, state and
private funds have been allocated to perform extensive renovations in the Ross Shaft. Refurbishment of the Ross
ShaftbeganinAugust2012,andover1100feetofnewsteelandassociatedgroundsupporthasbeeninstalledasof
December2013.Atotalof5159feetofnewsteelsetswillbeinstalledaspartoftheRossshaftupgradeproject,which
isexpectedtobecompletedbymid-2017.OncetheRossshaftiscompleted,aplannedrenovationoftheYatesShaft
willcommence.
SCIENCE FACILITIES
In addition to the considerable underground extent, several dedicated facilities exist at SURF to support science
activities.Onthesurface,anumberofspacesarebeingusedforstorage(includingdrillcore)andlimitedconstruction
activities.Threemainphysicslaboratoryspacesareavailable:theSurfaceLaboratoryandtwocampusesonthe4850
Level–theRossCampusandtheDavisCampus.
Surface Facilities
Key surface facilities at SURF supportscience activities at both the Yates and Ross surface campuses, including
administrativeactivities, educationand public outreachfunctions,the Waste Water TreatmentPlant (WWTP) and a
warehouseforshipping/receiving.Figure2showstheextentofthesurfaceproperty.
Whiletherearemanypossibilitiesofsurfacebuildingsthatcouldberenovatedtodirectlysupportscienceactivities,
twofacilitiescurrentlyfunctioninthatcapacity:theCoreArchiveandtheSurfaceLaboratory.
CoreArchive
Donated by Homestake-Barrick,SURF is the steward of 39,760boxesof drill core, which correspondsto a total
length of 91 km. Homestake core holes extend to 10,800feet below surface. An additional5,400feet of core were
addedtothecollectionaspartofthegeotechnicalinvestigationsonthe4850LforDUSEL.
The SD GeologicalSurvey has assisted with the developmentof an online database that so far includes 58,000+
entries,representing1,740drillholes.
SurfaceLaboratory
Renovationswereundertakenin2009inordertotransformaformerwarehouseintoalaboratory.Constructionwas
completedinearly2010,resultinginapproximately190m2oflabspaceinthetop-mostlevelofafour-storeybuilding
asshowninFigure3.Thefacilityincludesacleanroom(5.6m×6.6mwitha2.7mceilingheight)andcorresponding
dedicated air handling and filtration system as well as a tank that can be used as a water shield (2.8 m diameter ×
4mhigh).Thetankisinstalledinarecessedshaftinthecenterofthelaboratoryspace.Thelaboratorywasinitially
designedtomeettheneedsoftheLUXexperiment,butisnowusedtosupportmultipleresearchgroups.
FIGURE2. AplanviewofthesurfacecampusatSURF,whichcomprises186acres.
Underground Facilities
Anumberoflevelsrequiredtosupportfacilityoperationsinfrastructurecanalsoaccommodateresearchactivities.
However,the main infrastructurefor the supportof science activitieshas beendevelopedon the 4850Lwith formal
campuseslocatednearboththeRossandYatesshafts.
4850LRossCampus
The4850LRossCampusincludestheRossShaftand#6Winzeandencompassesasetoffourexistingexcavations
that were used as maintenance shops during mining activities. These former shops afford an economical means to
implementexperimentsorotherequipmentinatimelymanner.ThelayoutisshowninFigure4,includingthelocation
ofthecurrentelectricalsubstationandgenerators.
Two of the shop areas are currently in use. The SW area has been convertedinto a safety Refuge Chamber that
canaccommodate72peopleforup to96 hours.Itincludescompressedair,CO scrubbers,air conditioners,rations
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andcommunications.TheNWareaiscurrentlybeingusedbytheMAJORANAcollaborationtoelectroformcopperas
showninFigure5.
The NE shop will house the CASPAR acceleratorand a cleanroomis proposedfor the SE area to host a suite of
low-backgroundcountersandpossiblysupportotherresearchactivities,too.
FIGURE 3. Surface Laboratory. The recessed area with the tank isunder the grating in the foreground and the cleanroom is
locatedinthebackground.AhoistcanbeinstalledontheblueI-beamstructure.
TABLE 1. Footprint areas and volumes for the 4850L
RossCampus spaces. Thevolume fortheNE areaisde-
rivedfromlaser-scandata.
RossCampusLocation Area Volume
(m2) (m3)
NW(MAJORANAElectroforming) 184 504
NE 297 707
SE 137 376
SW(RefugeChamber) 121 332
FIGURE4. 4850LRossCampus.Fourexistingexcavationsarelabeled:NW,NE,SE,SW.
FIGURE5. TheMAJORANAelectroforminglaboratoryatthe4850LRossCampus.Thecleanroomislocatedontheright-hand
side.
4850LDavisCampus
A state-of-the-artlaboratorycomplexcalled the Davis Campushas been constructedat the 4850Lnear the Yates
Shaft.The Davis Campusrepresentsa $15.2MSouthDakotacommitmentusing state and privatefunds.New exca-
vation for the Davis Campus took place during September 2009 – January 2011, during which time 16,632 tonnes
(18,334tons)ofrockwasremoved.Ratherthanbeingtransportedtothesurface,areaswereidentifiedonthe5000L
(viathe4850L)forrockstorage.ShotcretewasappliedinboththeDavisCavern(averagethickness12.7cm)andthe
Transitionspace(averagethickness8.9cm).LaboratoryoutfittingbeganinJune2011andwassubstantiallycomplete
inMay2012;picturesareshowninFigure7.A finaloccupancycertificatewasissuedinJuly2012,whichspecifies
themaximumnumberofoccupantstobe62persons.
Thetwomainexperimentsareasarethe MAJORANA Lab/Transitionspace(43mL×16mW×4mH;3,648m3)
andtheDavisCavern(17mL×10mW×12mH;2,089m3),asshowninFigure6.Quoteddimensionsareaverage
values based on post-shotcrete laser-scan data. The total Davis Campus footprint consists of 927 m2 of laboratory
spaceand2,732m2 totalspace.
An array of extensometers is installed to monitor ground motion and convergence at the Davis Campus – data
collectedso farindicatenothingunexpected.Geotechnicalinterpretationswereperformedusingdrillcoreandother
rockmechanicsstudies[8].
Services provided within the Davis Campus include fire sprinklers and alarms throughout the area, potable and
non-potable(industrial)water,lighting,emergencylighting,ventilationandairconditioning.Abuildingmanagement
system providescontrolsthroughoutthe Campus. Cooling is providedwith two redundant50-ton(633MJ) chillers
supplyingchilledwatertothreeairhandlingunitsthatprovideventilationtoseparateCampusspaces.Chilledwater
isalsoavailableforexperimentstoconnectequipmentdirectly.Adedicated1500kVAsubstationprovidessufficient
capacity for the experiment and facility needs, with margin for future expansion. Emergency power for lighting is
providedwith batteriesin the lighting system to provideimmediate light, while a standby diesel generatornear the
campusprovidesupto24hoursofpowertoallsafetysystemsinthecampus.Thisincludeswaterpumpsinthenearby
Yatesshafttopreventwaterfromrisingintothecampusspaces.
While space is at a premium at the Davis Campus, two cutouts exist outside the clean space offering footprints
of33–50m2, withan averageceilingheightof3.7m.Thesespacescouldbe madeavailableto groupswithmodest
equipmentneeds.
FIGURE6. 4850LDavisCampusshowingthetwomainlaboratoryspacesandtheproximitytotheYatesShaft.
FIGURE7. PicturesoftheDavisCampusinMay2012afteroutfittinghadfinished:(upper)MAJORANADetectorRoom,(lower)
watershieldingtankinLowerDavisfortheLUXdetector.Aconsiderableamountofequipmenthassincebeeninstalledbyboth
collaborations.
RockOverburden
Whenconsideringthemuonfluxatkeylaboratoryspacesonthe4850L,sixgeologicalformationsareimportantto
consider:Grizzly,Flagrock,Northwestern,Ellison,HomestakeandPoorman.TheYatesMember(Unit)isthelowest
stratigraphic unit of the Poorman Formation and is important for developments on the 4850L. In addition, tertiary
Rhyolitedikesoccurthroughouttherockmass.
Thesurfacetopologyvariessignificantlythroughoutthe laboratorypropertyasshownin Figure8.Using average
rockdensitiesandpreliminarygeologicalmodeldatainadditiontorecenttopologicalsurveys,anestimateoftherock
overburdencan be determined as shown in Table 2. Overburdenuncertaintieswill be quantitativelyevaluated in an
upcomingpublication.Geochemicalcompositiondata for variousformationsare also being compiled from sources
suchastheUSGS[9]andothers.
FIGURE8. Topologicalcontoursoverlaidontopofanoutlineofthe4850L(showninblue).Variouscardinalcoordinatesare
indicatedwithredlines.TheOpenCutisaprominentfeatureonthesurfacetowardthewest.Contourlinesindicate20-footelevation
changes.
TABLE 2. Rock overburden estimates for different under-
ground laboratory locations at SURF, reflecting considerable
variationsinsurfacetopologyaswellasgeology.Uncertainties
ontherawoverburdenvaluesareontheorderofafewpercent.
4850LLaboratory RockOverburden
Location (m) (m.w.e)
DavisCampus–LUX 1464 4200
DavisCampus–MJD 1478 4300
DavisCampus–EntranceCutout 1561 4400
RossCampus–MJDElectroforming 1503 4300
RossCampus–LBNE 1386 3900
Cleanliness
CleanlinessattheDavisCampusismaintainedthroughacombinationoftransitionzonesandprotocolsaswellas
dedicatedcleaningstaff. When suppliesand equipmentare broughtfrom the dirty space into the clean space, items
eitherneedto be suitablyenclosedor cleanedinthe facility entranceCart Wash. Personneltypicallyenterthougha
seriesofroomswhereoutercoverallsanddirty-sidegearisremovedinfavorofcorrespondingcleanitems.Laundry
servicesarealsoavailableinthecleanspace.
When the laboratory is occupied, particle counts in all common areas are below 10,000/ft3. The MAJORANA
collaborationfollowsadditionalgowningprotocolstoachieveultra-lowcleanlinesslevelsintheirlaboratoryspaces.
AsummaryofcleanlinessstatesthroughoutvariousareasispresentedinTable3.Thefacilitydesignincludestwosets
ofshowers,butsofartheyhavenotbenecessary.
TABLE3. Medianparticlecountlevelsinvariouslaboratory
locationsduringoccupiedperiods.
DavisCampusLocation ParticleCount
(0.5m m/ft3)
Transition,LaundryArea 1290–8200
Transition,CommonCorridor 3160
DavisCavern,Lower 3400
DavisCavern,LowerCountingRoom 710
DavisCavern,Upper 450
Transition,MAJORANADetectorRoom 100–400
RadioactivityandRadon
SURF strives to providethe lowest possible radioactivityenvironmentfor experimentshosted within the facility.
Thiscommitmenthadbeenintegratedintothesitepreparationprocessfromtheearlydaysofthefacilitydesign,and
carriedovertotherealizationofthe4850LDavisCampuslaboratories.Theseeffortsincludesiteandenvironmental
characterizationincludingrockradioactivemeasurements,useoflow-radioactivityconstructionmaterials,andregular
monitoringofenvironmentalfactors,includingairborneradon.
ThenaturalabundanceofU/Th/KinHomestakerockisgenerallylow,especiallyincertaingeologicalformations
such as the Yates Amphibolite,which have been measured to contain sub-ppmlevels of U/Th. Samples from other
formationssuchastheRhyoliteintrusionscanbe30–40xhigherasillustratedinTable4.Whilenotaslowasthehost
Amphiboliterock,thelowest-activityconstructionmaterialsfortheDavisCampuswereselectedfromalargenumber
ofsamples [10,11,12].
TABLE4. PartialU/Th/KassayresultsforHomestakerocksamples
aswellaskeyconstructionmaterialsusedattheDavisCampus[10,
11,12].
Uranium Thorium Potassium
(ppm) (ppm) (%)
Amphibolite 0.22 0.33 0.96
RhyoliteDike 8.75 10.86 4.17
Shotcrete–LowActivity 1.52 2.17 0.55
Shotcrete–Standard 2.00 3.35 1.23
Shotcrete–FinishCoat 1.62 3.08 0.79
MasonryBlocks 2.16 3.20 1.23
Long-termundergroundradondatahavebeencollectedsince2009andattheDavisCampussinceJuly2012,shortly
afteroutfittingwascompleted.AsidefromthenormalfacilityventilationthatbringsfreshairviatheRossandYates
shafts, no extraordinarysteps have been taken to mitigate undergroundradon levels. Some research groupsemploy
a type of purging system to reduce radon locally for their equipment. As seen at other undergroundlaboratories, a
seasonaldependenceisbecomingapparentintheDavisCampustrends,withhigherradonlevelsobservedduringthe
summermonthsMaythroughSeptember.ThetotalaverageradonconcentrationforallperiodsattheDavisCampusis
approximately340Bq/m3withalowbaselineof150Bq/m3duringthewintermonths.
Othereffortstocharacterizephysicsbackgrounds(eg.,muons,neutrons,gammarays)invariousundergroundareas
were carriedoutbyresearchgroupsoverseveralyears[13, 14, 15]. Resultsfromrecentneutronflux measurements
collectedonthe4850Lareexpectedinanupcomingpublication.
CURRENTSCIENCE PROGRAM
Scienceeffortsthatstartedin2007duringre-entryintothefacilityhavegrownsteadilyovertheyears.Buildingonthe
legacyoftheRayDavischlorinesolar-neutrinoexperiment[16]thatbeganin1965attheHomestakeMine,morethan
a dozen research groupshave established undergroundresearch programsat SURF. Measurementshave been made
and samples collected from elevations ranging from surface to the 5000-footlevel, investigating topics in physics,
geology,biologyandengineering.ResearchprogramsthatareconsideredtobecurrentlyactivearelistedinTable5as
welltheirrespectivelocations.ThreemainphysicseffortsareunderwayatSURF.
LargeUnderground Xenon(LUX)
TheLUXexperimentisconductingadirectsearchforweaklyinteractingmassiveparticles(WIMPs)using350kg
ofpurifiedxenoninsideanultra-puretitaniumcryostatthatisimmersedinawatertankwith272,550liters(72,000gal-
lons)ofpurifiedwater.Followingcollisionsintheliquidxenonvolume,astrongelectricfieldmovesionizationelec-
tronsintothegasspaceatthetopofthedetector,andatotalof122PMTscollectscintillationlightfrominteractions
inbothxenonvolumes.
Members of the LUX collaboration have been active onsite at SURF since December 2009, when preparations
beganfordetectorassemblyattheSurfaceLaboratory.Aftercompletingdetectorassemblyandoperationaltestingon
surface,LUXbegantheirtransitionundergroundtotheDavisCampusinMay2012.WithstrongsupportfromSURF
personnel,thefully-assembledLUXdetectorwassuccessfullytransportedundergroundfromtheSurfaceLaboratory
in the Yatescage andinto theDavis Cavern– stringentlimits onaccelerationandtilt were notexceeded.TheLUX
spaceattheDavisCampusincludesacleanroomandacontrolroom,whichisseparatefromthemainlabspace.The
SURFwaterpurificationsystemandastorageareaforliquidnitrogenarelocatedneartheLUXequipmentbutoutside
thecleanspace.
TheLUXcollaborationrecentlypublishedresultsfromtheirfirstundergrounddatarun[17].
Majorana Demonstrator(MJD)
TheMAJORANAcollaborationisinvestigatingneutrinolessdouble-betadecayusingadetectorcalledtheDEMON-
STRATORconsisting40kgofgermaniumintwoultra-purecoppercryostatsandacompactleadshield. MAJORANA
expectstouseupto30kgofenriched76Ge.ThemaintechnicalgoaloftheDEMONSTRATORistoconfirmthattheam-
bitiouspurityrequirementsforatonne-scaledetectorareachievable[18].Thegroupalsohopestotestacontroversial
claimforthedetectionofneutrinolessdouble-betadecay.
Inordertosatisfytheverylowbackgroundrequirements,the MAJORANA collaborationhassetupalaboratoryat
the4850LRossCampustoproducetheworld’spurestelectroformedcopper,whichisthenmachinedatadedicated
machineshopattheDavisCampus.
The MAJORANA collaboration began work onsite starting in November 2010 with deliveries of equipment (in-
cluding the first germanium detectors) and then with preparations for the electroformingcleanroom. Production of
electroformedcopperbeganinJuly2011andabouteightmonthslaterthegroupstartedtomoveequipmentintothe
DavisCampus.
Center forUltra-lowBackground Experiments inthe Dakotas(CUBED)
CUBEDisaSouthDakotaGovernor’sResearchCenterthatisadministeredthroughtheUniversityofSouthDakota
andinvolvesphysicsresearchersandothersfromthemajorityofuniversitiesinthestate.Inadditiontoincreasingthe
SouthDakotaacademicinvolvementinSURFresearch,thecenterismaintainingafocusonareasofinterestcongruent
withplannedSURFexperiments,suchascrystalgrowth,low-backgroundcountingandisotopeseparation.
Alow-backgroundcountinglaboratoryhasbeensetupinadedicatedroomintheLowerDavisCavern.Thesystem
allowsdirect-gammacountingusinga1.2-kghigh-puritygermaniumcrystal,resultingin0.01–0.1ppbsensitivitiesto
U/Th.Initialoperationhasbegun,andproductioncountingisexpectedtostartinearly2014oncetheoutershielding
iscomplete.
AnotherCUBED projectthatproposestoinvestigateisotopicseparationandultra-purificationtechniquesisbeing
consideredfortheSurfaceLaboratory.Fundingisbeingsoughttodevelopalaboratorytosupportundergroundcrystal
growth.