Onthecover:TheLosAlamosNeutronScienceCenteratLosAlamosNationalLaboratory.

A Strategy for LANSCE Futures

Onthecover:TheLosAlamosNeutronScienceCenteratLosAlamosNationalLaboratory.

TABLEOFCONTENTS

Vision......................................................................................................................................1Background....................................................................................................................................2StrategyGoalsandPriorityActions(1-5years)...................................................................3StrategyGoals(>4years)...........................................................................................................4

StrategyDeepDive..............................................................................................................6ProtonRadiography.....................................................................................................................6NeutronRadiography................................................................................................................10NuclearScience...........................................................................................................................13MaterialScience..........................................................................................................................18IsotopeProductionatLANSCE................................................................................................21EstablishaMaterialsSurvivabilityLaboratory..................................................................24UltracoldNeutronFacility........................................................................................................27AcceleratorImprovements......................................................................................................30

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VISION

TheprimarymissionoftheLosAlamosNeutronScienceCenter(LANSCE)istomeasuredynamicmaterialperformanceandcharacterizethestructuralandnuclearpropertiesofmaterialsinsupportofLosAlamosNationalLaboratory’s(LANL)nationalsecuritysciencemission.

Amajorchallengeforstockpilestewardshipoverthenextdecadeswillbeunderstandingtheperformanceofagedandreplacementmaterialsthroughouttheentirestockpile-to-targetsequence(STS).CapabilitiesatLANSCEprovideanopportunitytoprepare;tocharacterizeandqualify;andtomeasurethedynamicresponseofmaterials,includingplutonium(Pu)andhighexplosives,atasinglesite.Additionally,LANSCEplaysfundamentalrolessupportingnuclearphysicsanddataunderlyingstockpileassessmentandcertificationandinproducingmedicalisotopes.

OurstrategicgoalsatLANSCEare:toenableadynamicPucapabilitywithimprovedresolutionattheProtonRadiographyFacility;toimproveourabilitytomeasureneutroncapturereactionsonradioactiveisotopes;toestablishaPuagingresearchcapabilityinAreaA;andtoimproveourabilitytocharacterizematerialsusingneutrondiffractionattheLujanCenter.AlltheseactionsareconsistentwiththeLaboratorystrategicgoalofbringingaMatter-RadiationInteractionsinExtremes(MaRIE)facilitytothesitetomeettheestablishedmissionneed.

Keypriorityactionsarethefollowing.

1. EnableandperformdynamicplutoniumexperimentsattheProtonRadiographyFacility.

2. InstallanewneutronspallationtargetattheLujanCenterin2020.ThenewtargetwillyieldsignificantimprovementsinthefluxandresolutionofkeVtoMeVneutrons.Thiswillenablenewnuclearphysicsopportunitiestoaddressoutstandingradiochemicalandnuclearforensicsissuesandnuclearphysicsmeasurementsinsupportoftheplannedneutrondiagnosedsubcriticalexperiments(NDSEs)attheNevadaNationalSecuritySite(NNSS),whilemaintainingtheLujanCenter’smaterialsciencecapabilities.

3. EstablishaMaterialsSurvivabilityLaboratoryinAreaA.Thisfacilitywillenablethescientificstudyofplutoniumagingandthecharacterizationandqualificationofspace-borneelectronicstoradiationinsults.High-powerprotonbeamoperationsinAreaAwouldalsosupporttheproductionofclinicallyrelevantlevelsofAc-225andasecondprotonradiographystation.

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4. Improvethehigh-energyneutronradiographystationwithalargerbeamdiameter,aturnkeyclassifiedcapability(withtheabilityforopenstorageofclassifiedparts),andadedicatedimagingsystem.

5. Continueinvestmentinthe45-year-old,800-MeVprotonacceleratortoensurereliableoperationswithhighavailabilityandenhancedperformancetosupportfuturemissions.SuchinvestmentswillbuilduponthesubstantialNNSAinfrastructureinvestmentsintheLANSCEacceleratoroverthepastfiveyears.

6. ContinuetocosteffectivelysupportaNationalNuclearSecurityAdministration-(NNSA)sponsorednationaluserprogramandotherimportantnationalmissionssuchasenhancedsurveillance,nuclearenergy,theproductionofmedicalisotopesfordiagnosisandtreatment,anindustrialelectronicsirradiationprogram,andfundamentalresearchinnuclearphysics.

BACKGROUND

LANSCEhasbeendeliveringcriticaldatainsupportofLANL’snationalsecuritysciencemissionsince1972.Thelong-termsuccessofLANSCEcanbeattributedtothecombinationofoneofthehighestpowerlinearprotonacceleratorsintheworldwithdiagnosticandexperimentalcapabilitiesthatarefocusedonnationalsecuritychallenges.LANSCEprovidesmaterialscharacterizationandtestingcapabilitynotavailableelsewhere.Thesecapabilitiesinclude:dynamicprotonradiography,materialcharacterizationusingneutronscatteringanddiffraction,nuclearcross-sectionmeasurements,andenergyresolvedandhigh-energyneutronradiography.

ThreeoftheLANSCEtargetstationsareNNSA-designatednationaluserfacilities(theProtonRadiographyFacility[pRad],WeaponsNeutronResearchFacility[WNR],andtheLujanCenter).TheLANSCEuserprogramhostedmorethan500usersfrom89institutions(and10countries)inthelatestruncycle(seeAppendix1).LANLscientistscollaboratewithmanyoftheexternalusersonprojectsofinteresttoNNSA,eitherthroughinter-Laboratoryagreements(LawrenceLivermoreNationalLaboratory,SandiaNationalLaboratories,AtomicWeaponsEstablishment[AWE],theFrenchAtomicEnergyCommission[CEA],etc.)oruniversitiesfundedthroughtheStockpileStewardshipAcademicAllianceProgram.

LANSCEmustcontinuetosupporttheongoingneedsofthenationwhilealsopreparingfortheMatter-RadiationInteractionsinExtremes(MaRIE)project,expectedtobecomeoperationalsometimeafter2030.ThisdocumentlaysoutastrategicvisionforLANSCEthatisresponsivetothecurrentandanticipatedneedsoftheNNSAforthenextdecade.

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STRATEGYGOALSANDPRIORITYACTIONS(1-5YEARS)

ENABLEADYNAMICPLUTONIUMCAPABILITYATTHEPROTONRADIOGRAPHYFACILITY

ThecurrentauthorizationbasisatpRadallowsfordynamicPuexperimentswithalimitof11gofPuand30gofhighexplosives(TNTequivalent).Suchexperimentswerelastconductedin2007.Heightenedsafetyconcernshavepausedsuchoperations.Wearecurrentlyworkingonthedesignofcontainmentsystems,removalofunneededlegacyequipment,andtheexpansionofourconductofoperationstoincludesafelyperformingdynamicPuexperimentswithinthecurrentauthorizationbasis.Firstexperimentsarescheduledtobeconductedin2020andwilladdresskeyquestionsintheweaponsprogram.Fieldingplutoniumexperimentsisexpectedtorequiresignificantlymoretimethanexperimentsusingonlyconventionalmaterials.ThiscouldsignificantlyimpactthenumberofexperimentsthatcanbeexecutedatthepRadfacility.GiventhedemandonthecurrentpRadfacilitywewouldestablishasecondfiringsiteforprotonradiographywithinAreaAifthedemandwarrantedsuchaninvestment.

REPLACETHELUJANNEUTRONSPALLATIONTARGET

RadiationdamagetothebeamentrancewindowrequiresthattheneutronspallationtargetattheLujanCenter(hereafterthe1Ltarget)bereplacedin~2020.Thisprovidesanopportunitytosignificantlyimprovethetargetperformanceforneutronswithenergiesbetween1keVand1MeV.Adesignthatimprovesourfigureofmerit(flux/resolutionsquared)byupto2ordersofmagnitude,withoutsignificantlyimpactingthefluxofthermalandepithermalneutrons,hasbeencompleted.WiththenewtargettheLujanCenterwillhavebest-in-classperformanceovertheseenergies,enablingmeasurementsofcaptureandscatteringreactionsonactinidesandotherisotopesandtotalneutroncrosssectionsonshort-livedisotopes.Thesemeasurementsareneededtounderstandradiochemicaltracersandneutrontransportandtoperformnuclearforensics.

IMPROVEHIGH-ENERGYNEUTRONRADIOGRAPHYCAPABILITY

LANSCEcurrentlyhastwofacilitiesforneutronradiography.ThermalandepithermalneutronsattheLujanCenterareusedtoperformenergyselectiveneutronimaging,whichenablesisotopespecifictomographyofmaterials.AtWNR,high-energyneutronsareusedtoradiographthickobjects,mostlytoinvestigatenondestructivesurveillancemethods.Thetoppriorityistoimprovethehigh-energystation.Theabilitytoaccuratelymeasureandselectneutronenergyenablesustoserveasatest-bedfornewradiographicconceptsandtechniques.Alargerbeamdiameter,aturnkeyclassifiedcapability(withtheabilityforopen

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storageofclassifiedparts),andadedicatedimagingsystemareallneededtoefficientlyfulfillcurrentandfuturemissions.

IMPROVEACCELERATORRELIABILITY

Acceleratorreliabilityimprovementsareneededtoensurethedeliveryofhigh-reliabilitybeamtoallareasofLANSCE.SignificantinvestmentsintheLANSCEacceleratorhaveenabledthemachinetooperateatthe120-Hzdesignfrequencyforthefirsttimesince2004.FundingforLANSCERiskMitigationactivitiesendedbeforeamoderndiagnosticsandamoderncontrolsystemcouldbefullyimplemented.Recentexperiencehasdemonstratedthatthesearetheprimarylimitationstoimprovingacceleratorperformanceandreducingmachinedowntimeandarethereforethehighestpriority.TheperformanceofthecesiatedsourceusedtogeneratetheH-beam(usedatWNR,Lujan,pRad,andtheUltracoldNeutronFacility[UCN])islimitingtheamountofavailablecurrenttoWNRandtheLujanCenter.Restoringthesourceperformancetopreviouslevelswouldenablethedeliveryof120micro-amps,whichwouldcompensatefortheapproximately25%reductioninthermalneutronfluxduetothenewLujantargetdesign.

STRATEGYGOALS(>4YEARS)

PHASE1AREAADEVELOPMENT

TheWNRfacilityhasprovidedavenueforelectronicsmanufacturerstotestcomponentresiliencytoneutronupsets.Whileneutronupsetsarethemajorconcernofground-basedandavionicselectronics,space-basedelectronicsareexposedtocosmicrays,whicharepredominantlycomposedofhigh-energyprotons.Themaintestingfacility(IndianaUniversityCyclotronFacility)forspace-electronicscomponentmanufacturersclosedin2014.Thedeliveryoflow-power(100nA)beamtoAreaAwouldenableLANSCEtofillthisnationalneed.LANLGlobalSecuritysponsors,theNationalAeronauticsandSpaceAdministration(NASA),andindustrialusershaveexpressedinterestinsuchafacility.ThiswouldbearequiredfirststepinthedevelopmentofaPuagingfacilityatLANSCE.

IMPROVEDNEUTRONDIFFRACTIONCAPABILITY

Asexistingpartsageandreplacementcomponentsareintroducedintothestockpile(potentiallymadethroughadvancedmanufacturingmethods),weneedtofullycharacterizetheirmicrostructuretoenableapredictivemanufacturingcapability.Weproposethedevelopmentofaflightpathdedicatedtothefullythree-dimensionalmeasurementoftexturethroughoutagivencomponentormaterial.Suchacapabilityisnotavailableanywhereelseintheworld.

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IMPROVEDDYNAMICRADIOGRAPHY

TheProtonRadiographyFacilityhasbecomeamajorfiringsiteforNNSAprograms.Themulti-framecapabilityiswellsuitedtomeasuringthedetonationandburningofhighexplosivesandtheresponseofmaterialsunderhighexplosiveloading.Twopotentialadvancementsthatwouldbenefitallprogramsarethedevelopmentofanachromaticlens,whichwouldimprovethespatialresolutionwithoutaffectingthefieldofviewandtheconstructionofasecondradiographicaxistoinvestigatethree-dimensionaleffects.Thesetwocapabilitiesarenotmutuallyexclusive.Oneorbothoftheradiographicaxescouldbecomposedofachromaticfocusingsystems.Replacingthecurrent3-framecameraswithnewlydeveloped10-framecameraswouldincreasethenumberofimageframesfrom31to70.

PHASE2AREAADEVELOPMENT

AsPuages,radiationdamagehasthepotentialtoalterthemicrostructureandaffectdynamicmaterialproperties.AsthesecondphaseofthedevelopmentofAreaA,anintenseneutronsource,drivenbya100-μAprotonbeam,wouldenableacceleratedagingofPu.Theradiationdamageinducedbyrecoilingfissionfragmentsmimicsthatofthenaturalalpha-decayprocess,whichcreatesU-235recoils.Thebeamlinewouldincluderudimentaryinsitumeasurementcapability.WithsuchacapabilityLANSCEwouldbeabletoacceleratetheagingofmaterial,characterizeitsmicrostructureattheLujanCenter,andinvestigateitsdynamicperformanceatpRad.Scopingstudiesareunderwaytoassessthevalueofsuchacapability,withitscomplementarybenefitscomparedtoAnnularCoreResearchReactorexposuresatSandia.

LANSCEACCELERATORUPGRADES

Thelong-termacceleratorupgradesarefocusedonsupportingthecapabilityimprovementslistedabove.IfthedevelopmentofAreaAproceeds,theIsotopeProductionFacility(IPF)kickermagnetmustbeusedtoenablesharingofthebeambetweenIPFandAreaA.Theprotonirradiationstationwouldrequire100nAofH+beam,energytunablebetween200and800MeV,whichwouldrequirereconfigurationoftheswitchyard.HighercurrenttoAreaAfortheMaterialsSurvivabilityLaboratorywillrequireimprovedtuningoftheacceleratorandreconfigurationofthebeamsharingbetweenIPFandAreaA.TosupportpotentialpRadcapabilities,theacceleratorwillneedtoincreasethenumberofprotonsperpulsetopRad.Asecondradiographicaxiswillrequireadoublingofthecurrenttomaintainthecurrentsingleaxiscapability.Anachromaticlenswouldrequiresubstantiallymorecurrent(studiesarebeingperformedtoevaluaterequirements)toachievethepotentialresolutiongainsoverthelargefieldofview.

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STRATEGYDEEPDIVE

Thefollowingsectionsdiscussthecapabilitydevelopmentsforeachtargetstationingreaterdetail.

PROTONRADIOGRAPHY

ThepRadtargetstationatLANSCEprovidesauniquecapabilitytotheNNSA’sStockpileStewardshipProgram:theabilitytogeneratemultiple-frameradiographicmoviesofdynamicexperimentsdrivenbyhighexplosivesorotherdrivers.TheLANSCEacceleratorcandeliveraneffectivelyunlimitednumberofradiographicpulsesof800-MeVprotonsattherelevantframerates(~1-μsinterframespacing).Thenumberofframesinanexperimentislimitedonlybytheabilitytoacquireandstorethedata.ThepRadfacilitycurrentlyincludesthecapabilitytorecordupto31framesofradiographicdataoneachdynamicexperimentincombinationwithotherdiagnosticssuchaslaser-basedvelocimetry.Thenumberofframescouldbeincreasedto70withthedeploymentofrecentlydeveloped10-framecameras.ThefacilityacceptsproposalsfromaroundtheLaboratory,theNNSAcomplex,andtheworldandfiresapproximately35dynamicexperimentsperannualLANSCEruncycle,mostinsupportoftheweaponsprogram.

TwoquestionscentraltotheStockpileStewardshipProgramareaddressedbythepRadexperimentalcapability.Tounderstandtheperformanceofanuclearweapon,onemustunderstandtheinitiationofdetonationinhighexplosivesandtheprogressofdetonationfrontsthroughexplosivesafterinitiation.Theseprocessesaredifficulttomodelnumericallyandmustbestudiedexperimentally,especiallyfortheinsensitivehighexplosivesusedinthenation’snuclearweaponstockpile.Thisisespeciallytrueatthetemperatureextremesencounteredthroughouttheentirestockpile-to-targetsequence.

Nuclearweaponperformancealsodependsonthereactionofmetalsandothermaterialstoshockedandunshockedhighexplosivedrive.CurrentareasofstudyincludenonlineareffectssuchasRichtmyer-MeshkovandRaleigh-TaylorInstabilitygrowth,failureofshockedmetalscausedbyshearorstrain,measurementoftheshockedequationofstateofrelevantmetals,andtheeffectofageandnewmanufacturingtechniquesonmaterialresponses.Theseissuesarecomplicatedbythepresenceofinherentlythree-dimensionaleffectsthataredifficulttostudythroughsimulationandexperiment.

ThepRadtargetstationatLANSCEwasconstructedin1998andconsistsofmultipleprotonimaginglensesinExperimentalAreaCcombinedwithhighexplosivehandlinganddiagnosticinstruments.(Apowdergunandapulsedpowersystemareavailableasadditionaldrivers.)Thefundamentalcomponentsofaprotonradiographysystemaretheprotondeliverysystem,thedynamicdriveandconfinementsystem,theprotonfocusing

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lens,theimagerecordingsystem,anysecondarydiagnostics,andthedataacquisitionsystemsusedtorecordtheradiographicandsecondarydata.

TheprotondeliverysystemconsistsoftheLANSCEaccelerator,aseriesofbeamsteeringandfocusingmagnets,andupstreamdiagnosticstomeasuretheincidentbeam.Theacceleratordeliversprotonsinmicropulses~100pslongseparatedby5nsoveranapproximately1-ms-longmacropulse.Anysetofthesemicropulses,eachcontainingabout3x108protons,canbeselectedfordeliverytoapRadexperiment.Typically,20micropulseswillbegroupedtogethertoformasingle100-ns-long,6x109protonradiographicframe,withupto31oftheseframesdeliveredtoeachdynamicexperiment—againwithanyspacingbetweeneachpairofframesin5-nsincrements.Upstreamdiagnosticsmeasureandcounttheprotonsdelivered.

Threedrivesystemsareavailablefordynamicexperiments:machinedhighexplosivesconfinedina6-foot-diametersteelconfinementvesselusedfor~60%ofthedynamicexperiments,a40-mmsmoothborepowdergun(30%),andthePrecisionHighEnergyDensityLinerImplosioneXperiment(PHELIX)pulsedpowercylindricalimplosionsystem(10%).Eachaccessesdifferentphysicsregimes:highexplosivescanreachthehighestpressures,thepowderguncansupplyasupportedshockinsteadofthehighexplosiveTaylorwave,andthePHELIXcansupplyasupportedshockinaconverginggeometry.Typicalexplosiveloadsareupto3poundsofTNT-equivalenthighexplosive:anabsolutelimitof10poundsTNT-equivalentisenforced.Thepresentconfinementsystemisqualifiedforhazardousorradioactivematerialssuchasvanadiumoruranium,butnotforthemorehazardousplutoniumorberyllium(Be).(NotethattheAcceleratorSafetyEnvelopeallowsfordynamicPuandBeexperiments.)

Threelenssystemsareavailableforradiographicexperiments:aone-to-onemagnification“identity”lens;athreetimes(x3)magnifyingmicroscope;andaseventimes(x7)magnifier.Eachlenshasadifferenttradeoffbetweenimageresolutionandfieldofview:120-mm-squarefieldofviewand250-micronimageresolutionfortheidentitylens,andproportionallysmallerfieldofviewandfinerresolutionforthex3andx7magnifiers.Eachlenscanbetunedfortheradiographicthicknessofagivenexperimentbyinstallingtheoptimal“collimator”tomaximizethecontrastandsensitivity.Onelimitationisthattheselensescanbesetforonlyasingleradiographicthicknessperexperiment;iftheexperimentchangesthicknessduringthedynamicevent,asalmostallhighexplosivelydrivenexperimentsdo,thenonlyasingleframeoftheradiographicmoviewillbeideallyfocused;theotherframeswillbe“chromaticallyblurred”bytheeffectofthechangingobjectthickness—byanamountproportionaltothedifferenceinthicknessbetweentheobjectinagivenframeandthesinglelenssetting.

Theprotonfocusingsystemgeneratesaprotonimagethatmustbeconvertedintodigitalradiographicdata.Thecurrentimagingsystemusesatwo-stagesysteminwhichascintillatingplateconvertstheprotonimageintoanopticalimagethatisrecordedbyanarrayoffastdigitalcameras.Thesecameraseachrecordmultipleimageson

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sub-microsecondtimescalesatnear-unityquantumefficiency.Thepresentsystemincludes7cameraseachcapableofrecording3framesandasinglesecond-generationcameracapableofrecording10frames,foratotalof31framesavailableforeachdynamicexperiment.Thenaturaltimescaleoftheimagingsystemisdrivenbythe50-nsdecaytimeofthescintillatingplastic,whichiswellmatchedtothefewmm/μsspeedofexplosivelydrivenexperimentsandthetenstohundredsofmicronspRadresolution.

Secondarydiagnosticsarespeciallytailoredtoeachdynamicexperiment.AbouthalfoftheexperimentsusephotonDopplervelocimetrytocontinuouslymeasurethevelocityofdiscretepointsonthesurfaceofanexperiment,whichcomplementstheabilityofprotonradiographytomeasurelocationsofthecontinuousinteriorfeaturesofanexperimentatdiscretetimes.Othersecondarydiagnosticsincludeperpendicularx-rayradiography,opticalandvoltagepins,andotherlight-baseddiagnostics.

ThepRadcapabilityincludestheabilitytofieldandrecordbothunclassifiedandclassifiedexperimentsuptotheSecretlevel,evenwithrestrictedneedtoknow.Approximatelyhalfoftheexperimentsconductedinrecentyearshavebeenclassified.Theexperimentalareacanbeconvertedintoalimitedsecurityareaforeachexperimentseriesasneeded,andapermanentlyinstalledclassifiedworkanddatastorageareaallowsprotectionoftheclassifiedinformation.

TheLANSCEProtonRadiographyFacilityistheonlyoperationalmany-framedynamicradiographicfacilityintheUnitedStates.TheclosestsimilarcapabilityisatLANL’sDual-AxisRadiographicHydrodynamic(DARHT)x-rayfacility,whichcangenerateuptofiveradiographicpulsesperexperiment(withtheadvantagethatitcanradiographsignificantlythickerobjectsthanispossibleatpRad).TheCygnusx-raymachineattheNevadaNationalSecuritySitecanradiographthinplutoniumexperimentsbutislimitedtotwopulses.Russiahasahigherenergyprotonradiographyfacility,withtheabilitytoradiographthickerobjectsathigherresolutionthanLANSCEorDARHT,butwithalimitednumberofframes.ChinaisconstructingorhasconstructedafacilitysimilartotheLANSCEpRadfacility.

POSSIBLEUPGRADESTOMEETFUTUREMISSION

TherearethreecategoriesofidentifiedmissionneedsthatthepresentpRadfacilitycannotmeet:1)theabilitytostudyveryhazardousmaterialssuchasplutoniumorberyllium;2)theabilitytoeitherfocusonverysmallobjectssuchasdetonatorsormaintainthebestfocusoverthedurationofanexperimentwithdrasticallychangingthickness;and3)theabilitytomeasurethree-dimensionaleffectsinasingleexperiment.

Potentialfacilityupgradescanaddresseachofthesemissionneeds.

ImplementadynamicplutoniumexperimentalcapabilityatpRad.ThiscapabilityiscurrentlybeingdevelopedwiththesupportofLANL’sweaponsprogram.Initially,thecapabilitywill

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belimitedto11plutonium-equivalent-gramsofmaterialdrivenbyupto30TNT-equivalent-gramsofhighexplosive(perexperiment).Toenablethecontainmentofveryhazardousmaterials,adouble-walledcontainmentsystemisbeingdesignedtocomplementtheexistingsingle-walledconfinementsystem.Theinnervesselisdesignedtofullyconfinethedynamicexperimentandhazardousshotdebrisandwillbedisposedofintactaftereachexperiment.Theoutervesselwillprovidesecondarycontainmentandwillbereusedformultipleexperiments.ThefirstPuexperimentswillinvestigatethereactionofPutoshockloadsandarenowbeingdesigned.Thecurrentschedulecallsforfieldingin2020.Asmentionedabove,fieldingtheseexperimentswillrequiresignificantlymoretimethanconventionalexperiments.Ifthereisaneedformorethan1-2suchexperimentsperruncycle,itislikelythatasecondprotonradiographicstationwouldneedtobeestablishedinAreaAtomeetthedemandforthefacility.

Improveradiographicresolution.ThedevelopmentofahigherresolutionsystemwithfasterdetectorsiscloselytiedtothedevelopmentofaprotontransportanddetectorsystemforexperimentsattheMaRIEfacility’sMultiProbeDiagnosticHall,whichisexpectedtofieldexperimentsthataretypicallyafewmillimeterorsmallerinsize.

Twonewsystemsarebeingstudiedtoimprovetheresolutionoftheprotonradiographs.

1. Thefirstisax21magnifyinglensthattradesofffieldofviewforenhancedresolution.Thissystemwillhaveafieldofview5x5mmandanimageresolutionof10μm.Combinedwithafasterprotondetectorandimagingsystems,itwillpermitexperimentsonasmallerscalethanpossiblewiththeexistinglenses.ThetotalcostofdevelopingsuchalensanddetectorsystemisdominatedbytheR&Dcostsforthedetectorsbutisexpectedtobelessthan$1M.

2. Thesecondnewlenssystemnowunderdevelopmentisan“achromatic”protonlens,whichwillhaveanoptimalresolutionsimilartotheexistingidentitylensbutwillbefarlesssensitivetochangesinthicknessofthedynamicobject.Insteadofthechromaticblurmentionedabovebeingproportionaltothechangeinthethickness,itwillbemuchmoreweaklycoupled.Theexistenceofsuchalenswouldenableaclassofexperimentswithvariablethickness,witheithertemporalorspatialthicknessgradients.Anexampleofthelatterisadetonationfrontpassingthroughhighexplosive(radiographicallythin)thendrivingashockwaveinametalplate(radiographicallythick).WiththeexistingpRadlenses,suchanexperimentistechnicallychallengingorevenoutofreach;withanachromaticlens,itwouldberelativelystraightforward.Thecostofsuchalensisdrivenbytheacquisitioncostofhigh-powerelectromagnetsandisexpectedtobe$5-10M.

Enableexplorationofthree-dimensionaleffects.Asecondprotonbeamlineintheexperimentalareaatanangletothefirstwouldenabletheexplorationofthree-dimensionaleffects,withmanyimageframesinbothaxes.Experimentsneedingthiscapabilitywouldbeinvestigationsofthree-dimensionaleffectsinhighexplosiveinitiationandnonlinearmaterialfailureeffects.Theseareknowntoexistandbeimportantbutareextremely

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difficulttoaccessexperimentally.ThebestthecurrentpRadfacilitycandoistofieldtheexactsameexperimenttwiceandradiographitfromdifferentangles.Thisisnotsufficientforstudyingstochasticandnonlineareffects.Atwo-axiscapabilitycouldbeimplementedbytakingadvantageoftheH-ionstosplittheincomingbeamintotwosecondarybeamswithidenticaltimestructuresthatareseparatelytransportedtothesameexperimentfromdifferentangles.Figure1showsaconceptualdesignofsuchamagnetsystemthatwouldfitwithintheexistingAreaCfootprint.Thecostofsuchacapabilityisdrivenbytheacquisitionofthemagnetsandcorrespondingpowersuppliesandisexpectedtofallintothe$5-10Mrange.

Anyoftheseupgradestothefacilitycouldbecompletedinafive-yeartimespanandcouldbelocatedeitherintheexistingExperimentalAreaCfacilityorinanewprotonradiographyfacilityinExperimentalAreaA.

Figure1.Conceptualdesignofadual-axiscapabilityforprotonradiographyinAreaC.

NEUTRONRADIOGRAPHY

ManyaspectsoftheLANLmission,includingstockpilestewardship,fundamentalresearch,globalsecurity,andnuclearenergy,requireimagingwithpenetratingradiation.Thisneediscurrentlysupportedbybroadx-rayimagingcapabilities,protonradiography,andalimitedsetofneutronimagingcapabilities.Theabilitytocombinedatafrommultipleneutron

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energyrangeswithx-rayandprotonimagingdataatthesamelaboratoryisonlyavailableatLANLandwouldaddpowerfulnewinsightforcomplexobjects.

Inspiteoftheseexistingcapabilities,thereremainkeyareaswherenoexistingimagingcapabilityexists.Thisleadstoexpensivedestructivetesting,theinabilitytoreuseparts,andalackofunderstandingofimportantphenomenon.Investmentinneutronimagingcapabilitiescouldrealizesignificantgainsintheseareas.Theseinclude

• imagingofthick,highZweaponspartsandassemblies;• imagingoflowZmaterialsshieldedbyhighZmaterialsincludingliquidsandgases;• imagingofnuclearfuels;• imagingtheisotopicdistributionincomponents;and• quantitativeimagingofindividualmaterialsandcombinationsofmaterials(e.g.,

polymeronmetalinterfaces).

Aclassifiedaddendumonspecificareasofinterestforimagingisavailable.LANSCEpossessesacombinationofneutronimagingcapabilities.Theavailabilityofcold(4to13A),thermal(25meV),epithermal(1eVto10keV),andhigh-energy(0.1to400MeV)neutronsoffercomplementarycapabilitiesandimagingtechniquesthatspanapplicationsfromcharacterizingtheisotopichomogeneityinnuclearfueltothetomographicimagingofadinosaurskull.ThecurrentcapabilityhasgrownwithsupportofaPrincipalAssociateDirectorateforScience,Technology,andEngineering(PADSTE)smallequipmentgrantandinvestmentfromafewprograms(primarilyEnhancedSurveillanceandNuclearEnergy).LANSCEprioritiestoenhancethiscapabilityareto

1. developthehigh-energyneutronradiographycapabilityintoaturnkeyoperationwiththebeamdiameterneededtoimagemission-relevantassemblies,includingclassifiedoperations,and

2. developandinstrumentadedicatedthermalimagingbeamlineintheLujanCenter.

Thecurrentcapabilitiesandfutureenhancementsarediscussedbelow.

FASTNEUTRONRADIOGRAPHY

Fastneutronimaging(100keV-400MeV)workcurrentlyusesflightpath60RatWNR.Theenergy-integratedneutronfluxisapproximately106ncm–2s–1andthebeamareais30cmx20cm.Theradiographicimagingsystemreliesonborrowedcomponentssuchasalens-coupledcamerasystemfromtheUnitedKingdomandfast-gated(1-20ns)camerasonloanfromtheIntelligenceandSpaceResearch(ISR)Division.Tomographyofthicksystemscantake24hoursormoreofbeamexposure,requiring24/7attendanceforclassifiedcomponents.Thecurrentflightpathisintheegresspathforflightpath30R,usedbyindustrialusersandforeignnationals.

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Tofulfillthismission,thefollowingimprovementsareneeded:

• Theareaoftheneutronbeamenlargedandmadeuniform.A40cmx40cmorlargerbeamareaat~20miscriticaltoenabletheimagingoflargerparts.(Notethataninherentstrengthoffastneutronsistheabilitytopenetratelargeparts).Thisrequiresshutter,collimation,andshieldingmodification.Thecollimationandshieldingshouldhavetriplecollimationaftertheshutterandsubstantialshieldingneedstobeplacedaroundthecollimators.

• Installationofapermanentstructurethatwillenableafasttransitionbetweenunclassifiedandclassifiedoperations.Theabilitytohaveopen,unattendedstorageofclassifiedcomponentsisasecond-levelpriority.Thiswouldsubstantiallyreducethecostandrisksofthecurrentoperations.Ifbuiltthiswouldsupportasmanyotherclassifiedexperimentsaspossible(notjustradiography).

• Investmentinadedicatedtomographiccapability.Thisincludesmotionstages,imagingsystems,dataacquisitionsystem,andcomputersthatarededicatedtotheradiographicflightpath.Adedicatedtime-of-flightimagingsystemisthemostcriticalneed.

Giventheaboverequirements,implementingthisinfrastructureonflightpath15Rwouldbethemosteconomicaloption.

THERMALANDEPITHERMALNEUTRONIMAGING

Thermalandepithermalneutronimagingusesflightpath5attheLujanCenter.Neutrontime-of-flightinformationcanbeusedtomakeisotope-specificimagesofobjects.ThiscapabilityatLANSCEisaresultoftheshortneutronpulsewidthandaspeciallydevelopedmicro-channelplate(MCP)detector1.Thermalimagingisperformedonlargerobjects(8cmto1mdiameter)andenergyresolvedimagingwiththetime-of-flightdetectorispossibleforsmallerobjects(3cmx3cm),witharesolutionofapproximately50μm.Toadvancethiscapabilityweneedtodothefollowing.

1. Developadedicatedflightpathforthermalneutronimaging.Currentlythiscapabilitysharesflightpath5withtheenergyresolvedimaging.Thisinhibitsthedevelopmentofthermalneutronradiography,whichhassubstantialpotentialapplicationsinawidevarietyofLaboratorymissionareasincludingforDefenseProgramsandGlobalSecuritysponsors.

2. DeployalargerMCPdetectorforenergy-selectivenuclear-resonanceimaging.Thiswillenableincreasedthroughputforlargerobjectsandisessentialforcomputedtomographyoflargerobjects.

1A.S.Tremsin,etal.,J.Nucl.Mater.440633-646(2013).

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NUCLEARSCIENCE

Theperformanceofanuclearweaponoranuclearreactorcannotbeunderstoodwithoutaccurateknowledgeofthefundamentalnuclearprocessesresponsibleforenergyreleaseinadevice.Fissioncrosssections,neutroncapturereactions,neutronscattering,andnuclearfusionreactionsallcontributetoaweapon’sperformance.Inaddition,isotopicsignaturesmaybeusedasdiagnosticstounderstandboththeU.S.stockpileandforeignthreats.RecentnuclearscienceworkatLANSCEhasconcentratedonpreciselymeasuringnuclearfissionproperties(fissioncrosssections,neutronoutputspectra,fissionfragmentyields,andkineticenergies)andneutroncapturereactionsatweapons-relevantenergies.Inthenextseveralyearsthis“precisionfission”programwillbecompleted,deliveringthefissionreactiondataneededtounderstandandpredictweaponperformance.Goingforward,thenuclearsciencemissionatLANSCEwillfocusonmeasurementstosupportradiochemicalanalysisofpastnucleartests,providephysicaldataforthetechnicalnuclearforensicsprogram,andsupporttheneutrondiagnosedsubcriticalexperiments(NDSE).Tosupportthesefuturemissions,LANSCEproposesto

1. exploitthehigh-energy(WNR)andkeV(LujanCenter)neutronspectrafornationalsecurityscience;

2. developflightpath13toenabletheaccuratecalculationofneutroncapturecrosssectionsonshort-livedisotopes;and

3. advanceandevolveexistingdetectorsystemstosupportfutureprogramsincludingNDSE.

ThesuccessofthisprogramreliesonthecapabilitythatwillbeprovidedbytheredesignedLujanspallationtarget,whichwillyieldupto2ordersofmagnitudeimprovementincapabilityintheenergyrangebetween1keVand2MeV.Thetargetisscheduledtobereplacedin2020.ThenewdesignfortheLujantargetisdiscussedbelow,followedbytheproposednewcapabilities.

THELUJANTARGETREDESIGN2

AmajorfocusoftheLujanCentertargetredesignwastoenhancetherangeofnuclearsciencequestionsthatcouldbeaddressed,whilemaintainingthematerialssciencecapabilities.Theprimarylimitationoftheexistingtargetisthepoorneutronenergyresolutionandlowfluxabove1keV.Theenergyrangeofhighestimpactforneutroncapturemeasurementsisfrom500eVupto2MeV.Theresolutionisdrivenbythemoderatorresponsefunctionandtheprotonpulsewidth.Thelowfluxisaresultofapriordesigndecisiontooptimizethethermalneutronflux.Whileitisnotpossibletoderiveasingle“figure-of-merit”(FOM)thatcanbeappliedtoallexperiments,acommonlyusedfigureistheneutronfluxdividedbythesquareoftheenergyresolution,f/DE2.(Theenergy2Theredesignwasrequiredbecauseoftheapproachingend-of-lifeofthecurrentLujantarget.

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resolutionisdirectlyproportionaltotheprotonpulsewidth.)Figure2showstheimprovementinthisFOMrelativetothecurrenttargetfortwocases:oneinwhichtheflightpathsareleftastheyare(“current”)andanotherwheretheflightpathsarerealignedsothedetectorsandsampleshaveadirectline-of-sighttothemoderator(“centered”).

Therecent239Pu(n,g)measurementwiththeDetectorforAdvancedNeutronCaptureExperiments(DANCE)illustrateshowtheimprovedtargetwillimprovequalityandreliabilityofthemeasurementsthatcanbeperformed.Figure3showsthemeasuredcrosssectionwithstatisticalandsystematicuncertainties.Theuncertaintiesabove200keVaredrivenbyacombinationofinstantaneouscountrate,energyuncertainty,andfissionandscatteringbackgrounds.Theenergyuncertaintycomesdirectlyfromthebroadprotonpulsewidthandthemoderatorresponsefunction,bothofwhichareimprovedinthenewtargetdesign.

Figure2.TheimprovementintheFOMfortheredesignedtargetunderarangeofpulsestructures.Notethatforisotopeslike88Y,pulsedeliveryflexibilityiscriticalformaximizingthetargetredesignimpact.

DEVELOPMENTOFFLIGHTPATH13

TheDeviceforIndirectCaptureExperimentsonRadionuclides(DICER),currentlyunderdevelopmentonflightpath13,willoffertheopportunitytodirectlymeasurenuclearpropertiesonextremelyradioactivesamples.Thiscapabilityisbeingdevelopedtoaddressfuturemissionneeds:thedeterminationofdiagnosticquantities(particularlythosethatareneededforboththeradiochemistrydetectorandtracerprograms)andnuclearforensicsefforts.TherearesignificantgapsintheknowledgeofthecrosssectionsrelevanttoradiochemicaldetectorsthatDICERcanfill.Thiscapability,whencoupledwiththenewtarget,willprovidethenucleardataneededtoopenanewwindowintoradiochemistrydiagnosticsandnuclearforensics.

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TheconceptbehindDICERrequiresthemeasurementofatleast50well-resolvedresonanceswithsufficientstatistics3.Whilethisisstraightforwardforwell-deformedrare-earthandactinideisotopes(TmandU,forexample),itpresentsanexperimentalchallengeforisotopeswithlowerleveldensities.

Figure3.Theneutroncapturecrosssectionfor239Pu(n,g)measuredwithDANCEcomparedtopastmeasurements,evaluations,andreactiontheorycalculations.Astheneutronenergygrowsabove200keV,theuncertaintiesgrowrapidly,limitingtheabilityofthemeasurementtodistinguishbetweentheoreticalmodels.

ADVANCINGEXISTINGINSTRUMENTSANDDEVELOPINGFUTUREMISSION

AstheChi-Nueffortcompletestheneededmeasurementsneededforthepromptfissionneutronspectra(PFNS)of239Puand235U,anopportunityexistsforotherprogramstotakeadvantageofthepreviouslymadesignificanthardwareandsoftwareinvestments.BeyondsimplymeasuringthePFNSofminoractinides,thedetectorcouldberepurposedtomeasureinelasticneutronscatteringcrosssections.Thelackofsuchdatacurrentlyallowssignificantfreedomintheevaluationprocess,makingtheintegralmeasurementsfromexperimentslikeJezebelandFlatToplessstringentthantheycouldbe.TheexistingChi-Nuscintillatoranddataacquisitioninstrumentationwouldbeanidealstartingpointforsuchaprogram.AconcepttomeasuretheinelasticcrosssectionhasbeendevelopedincollaborationwiththeUniversityofCalifornia,Berkeleyandisbeingdisseminatedthroughtheinter-agencynucleardatacall.ThesecapabilitieswilldirectlysupporttheinterpretationoftheNDSEdiagnostic.

TheLow-EnergyNZ(LENZ)detectorbeingdevelopedatWNRmeasureschargedparticlereactions(neutronin,chargedparticleout).WhileexisitingprogramsarelimitedtoWNRduetolimitationsofthecurrenttargetattheLujanCenter,thenewtargetwillenablemeasurementswithLENZ,thatcanaddressarangeofissuesfromdevicediagnosticsto

3P.E.KoehlerLA-UR-14-21466(2014).

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yielddeterminations.Asasimpleexample,arsenic-73andarsenic-74areshort-livedisotopeswithpositiveQ-valuesfor(n,p)and(n,α).Thechargedparticlereactionchannelschangethedetectedproductsfromarsenictootherelements,complicatingtheradiochemicalinterpretation.Withthenewtarget,LENZwillbeabletoperformthemeasurementinthekeVregime,wherenomeasurementscurrentlyexist.

Currenttransportandsimulationtoolshavewell-knowndeficienciesing-rayproductionfromneutroncapture.Forapplicationsfromradiationsafetytoradiationeffectsthatdependonthespectralinformation,suchdeficienciesproducepoorlyquantifiedsystematicuncertainties.DANCEhasbegunacampaignofneutroncapturemeasurementsfocusedonstudyingg-emissionfollowingneutroncapture.Thereisanopportunitytousethisexperimentalinformationtodevelopthenecessaryunderlyingsimulationtoolsformodelingandbenchmarkingkeyg-raychannelstoexperimentaldata.ThesetypesofmeasurementsoffertheopportunitytoexpandthefundingprofilefornuclearsciencebeyondDefenseProgramsinNNSA’sNA-10.

TARGETEDINVESTMENTSINTHENEXTFIVEYEARS

ThehighestpriorityinvestmentfortheLANSCEnuclearscienceprogramisthereplacementoftheLujanspallationtargettoensurecontinuedoperationbeyond2020.Theproposedredesign,withtheenhancementsfornuclearscience,willallownext-generationmeasurements.Thisneedhasbeenrecognizedandthespallationtargetreplacementisontrack.Successofthenuclearscienceprogramdependsonavailabilityofwell-characterizedactinideandradioisotopesamplesfromIPF,whichwillrequireactinidehotcellsforprocessing.Theseco-locatedLANSCEcapabilitieswillbevitaltothesuccessofDICER,radioisotopemeasurementswithLENZ,andfullexploitationofDANCEcapabilities.

Prioritized,near-termneedsfornewinvestmentintheLANSCEnuclearscienceprogramarethefollowing.

1. Stabilization(withsmallgrowth)ofthescientificandtechnicalstaff.2. IncreasedinvestmentintheDICERcapabilitytoexpeditetransitionfrom

developmenttofirstsciencemeasurements.3. RealignmentofnuclearphysicsflightpathsatLujantooptimizefluxonsample.4. Detectordevelopmentfornext-generationexperiments.

ALONG-TERMOPPORTUNITYFORENHANCEDIMPACT

ThecurrentsuiteofmeasurementsatLANSCEfacesafundamentallimitation:atsomepoint,theisotopesofinterestsimplybecometooshortlivedtomakeintoasampleanddelivertotheexperimentalsite.Anotherapproachhasbeenexploredintheliteraturewheretheisotopeofinterestiscreatedandmeasuredessentiallysimultaneously.Thiswouldentailusingaspallationneutronsourceasacontinuallyrefreshedneutrontarget.Thebasicideais

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tohave~1mballofthermalneutronsinequilibrium.AtthekeVtoMeVenergiesofinterestforreactionmeasurements,thermalneutronsareeffectivelyatrest.Ifabeamofradioisotopespassesthroughtheneutronball,reactionstakeplace,butkinematicsmoveallofthereactionproductsthroughtheneutronballandouttheotherside.TheEuropeannuclearphysicscommunityhasbeenconsideringthephysicsofionstoragerings,withcyclefrequenciesontheorderofMHz.Combininganionstorageringwithaspallation-generatedneutrontargetcouldprovidesixordersofmagnitudeincreaseinradioactivebeamluminosity.SuchafacilitywouldenablemeasurementsnotpossibleevenattheFacilityforRareIsotopeBeams(FRIB).Astorageringcanperformverysensitivemassmeasurements,easilyidentifyingreactionproductsinmass-changingreactionslike(n,g)and(n,2n).ThisconceptwassetforwardbyReifarth4.Ifimplemented,thiscapabilitywoulddirectlyaddressneutron-inducedcross-sections.Existing,underconstruction,andplannedradioactivebeamfacilities,includingFRIB,arealldesignedtodeliverintensebeamsofradioisotopes,butarenotdesignedtomeasureneutronreactioncrosssections.Atbest,theywilloffertheabilitytomeasureunderlyingnuclearstructurepropertiesusedbytheoreticalmodelstopredictreactioncrosssections.Thisconceptisparticularlywell-suitedtoaddressquestionsofinteresttoNNSA

Thisconceptwouldrevolutionizeneutroncross-sectionmeasurements.Itwouldprovidedirect,complete(n,xn)and(n,g)reactioncrosssections.Experimentalbackgroundslimitingneutroncapturemeasurementsfrom10keVupto2MeVwouldbeeliminatedbecauseofthenewapproach.Newmeasurementsof(n,2n)wouldbeaccessibleinthefastneutronenergyregimeforisotopeswithhalf-livesdowntominutes.Thequestionsthispossibilityraisesareastantalizingasthemeasurementrevolutionitoffers.Whatnewweapondesignissuescanwecontemplatewhenallrelevantcrosssectionsareexperimentallymeasuredtobetterthan10%?Doesthisofferthepossibilityofdeterminingallcross-sectionuncertaintiesforweaponsandotherapplications?Ifahugeswathofmarginiseliminatedindesign,howdoesthatchangehowweperformourmission?

Theconceptrequiresthreetechnicalcapabilities:ahigh-intensityprotonspallationsource,anisotope-separationOnLine(ISOL)rareisotopeproductiontarget(thesearetypicallydrivenbyanintenseprotonaccelerator),andanionstoragering.Independently,thesethreepiecesareunderstood.LANSCEprovidestheprotonpieceofthefirsttwo.

Giventhesweepingscaleofthenewmeasurementsthiscouldoffer,investigatingwhattheimpactofsuchacapabilitywouldbeforLANLmissionseemsprudent.Furtherstudyisneededtounderstandhowsuchaneutronballtraversedbyionsmightwork.Suchafacilitywouldbedecadalbynature,butsmallinvestmentsareneededtounderstandthechallengeandpossibilitiesofthisconcept.

4R.ReifarthandY.A.Litvinov,Phys.Rev.AB,17,014701(2014),R.Reifarth,etal.,Phys.Rev.AB,20,044701(2017).

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MATERIALSCIENCE

Thesuccessofthescience-basedStockpileStewardshipProgramdependsuponhavingconfidenceintheperformanceofagedmaterialsandcomponentsmanufacturedusingdifferentprocesses.While“admiraltests,”suchassubcriticalexperimentsattheNNSS,willbeacriticalpartofthisprogram,anunderstandingoftheunderlyingmanufacturingscienceisneededtomakethemostefficientuseoftheseexpensiveresources.ThematerialsscienceprogramatLANSCEisdedicatedtothecharacterizationofmaterialmicrostructure,residualstress,andtextureincomponentsmadewithnewmanufacturingmethodsandinagingmaterials.ThefollowingtwoprioritiesforadvancesinmaterialcharacterizationcapabilityatLANSCEwillenablethesemeasurements.

1. Turnkeyclassifiedresidualstressandtexturemeasurements.2. Adedicatedlong-termaging-effectsinstrument.

TURNKEYCLASSIFIEDRESIDUALSTRESSANDTEXTUREMEASUREMENTS

Weproposeaninstrumentinoneoftheexistingflightpathsbededicatedtospatiallyresolvedmeasurementsofresidualstressandtextureinclassifiedcomponents.Overthelast15years,roughlytworesidualstressmeasurementsonclassifiedpartshavebeenrequiredperyear,includingmeasurementsonberylliumwelds,uraniumshellsforthehydroprogram,gasbottles,andmostrecently,foradditivelymanufacturedcomponents.Giventheupcominglifeextensionprograms,thejointtechnologydemonstrator,andpotentialnewsystems,webelievethatthedemandforresidualstressmeasurementswillcontinuetogrow.Texturemeasurementsincomponentsmadefromanisotropicmaterialssuchasberyllium,uranium,anduraniumalloysareespeciallyimportantasistheabilitytomeasuretheresidualstressandtextureundertherangeofenvironmentsthatspanstheSTSenvironment.

WhilethecurrentSpectrometerforMaterialsResearchatTemperatureandStress(SMARTS)instrumentprovidesworld-classresidualstressmeasurements,adedicatedinstrumentwouldenablesignificantimprovements.TheSMARTSdesignwascompromisedtoallowforbothinsitumeasurementsunderextremeenvironmentsandresidualstressmeasurements.Theopenhutch,builttoaccommodatethecomplexandlargesampleenvironments,resultsinelevatedbackgroundlevels,whichincreasethetimerequiredtoperformanygivenexperiment.Switchingbetweenspatiallyresolvedmodesrequiresthattheradialcollimatorsbereconfigured,atime-consumingprocessthatrequiresrecalibratingtheinstrument.

Thereisnocapabilityworldwidetoperformspatiallyresolvedtexturemeasurementsatdepthincomponentsmorecomplicatedthanaplate.Destructivetesting(componentsectioning)mustbeperformedtomakesuchmeasurements,whichpreventsanysubsequentperformancetestingofthecomponent.Sincemanyofthecomponentsof

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interesttoNNSAareclassified,theabilitytoeasilyperformclassifiedexperimentswithouttheneedfor24/7attendancewouldprovideasignificantbenefit.Figure4showsamapofthethermalexpansionofahydro-formeduraniumhemispherethatwascalculatedforspatiallyresolvedtexturemeasurementsonHIPPO.Onecanseethatthethermalexpansionvariesby~30%,whichwillcauselargedistortionsandevenplasticdeformationwithrelativelysmallchangesintemperature.

Amodestequipmentinvestmentwouldbenecessarytoimplementtheproposedcapability.Theleastexpensiveoptionwouldbetodevelopthecurrentflightpath2(SMARTS)beamlineasitalreadyhasthedetectorsandneutronguide.Thiscomes,however,atthecostoflosingthecapabilityforinsitumeasurementsattemperatureandstress,etc.Boththedormantflightpath1(NeutronPowderDiffractometer,NPDF)andflightpath16(High-resolutionSpectrometer,PHAROS)offerspaceforadedicatedspatiallyresolvedinstrumentwithoutimpactingcurrentcapabilities.Weestimatethecostofsuchaninstrumentat~$3Mplusthecostofaclassifiedenvironment.Useoftheseflightpathsdependsuponleavingtheexistingmercuryshuttersystemsintact.

ADEDICATEDLONG-TERMAGING-EFFECTSINSTRUMENT

Aninstrumentdedicatedtounderstandingtheeffectoflong-termagingonmaterialssuchasPuGaalloyswouldbeofgreatbenefittotheweaponsprogram.Thiscapabilitywouldbewellsuitedtotheflightpath1(NPDF)beamlineandcouldberealizedintwosteps.Measurementsinrelativelysimpleenvironmentscouldbeginalmostimmediately,withmulti-modalmeasurementsincomplicatedsampleenvironmentsbeingrealizedwithmodestinvestment.

Figure5showsaWilliamson-Hall(W-H)plotmadeusinghighresolutiondiffractiondatacollectedonSMARTSonasampleofaged(4monthsbelow50K)Pu-2wt%Gaandonthesamesampleafterannealingfor48hoursat673K.TheW-Hplotsallowonetomakeasemi-quantitativedeterminationofthedislocationdensity,whichinthiscaseis~5xgreaterintheagedmaterialthaninthesamesampleafterannealing.Adedicatedaginginstrumentwouldenableinsitumonitoringoftheevolutionofdamageduringtheextendedagingtime(months)andlongannealingperiod.

Figure4.Coefficientofthermalexpansionasafunctionofpositiononaformeduraniumhemisphere.

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Continuedconfidenceintheagingstockpilerequiresunderstandinghowmaterialsrespondtotimeinserviceindifferentenvironments.Environmentscouldincludecyclingbetweennon-ambienttemperatures(aboveandbelowroomtemperature),chemicalenvironments,ionizingradiation,orstress.MaterialssuchasPualloys,highexplosives,uranium,anduraniumalloysareofconcern.ProgramareasoutsideoftheNNSAmissionspacehavesimilarmeasurementneeds.Recentemphasisonmaterialsin“harshenvironments”suggestslong-timeagingmeasurementsonhightemperaturesuperalloysinsupercriticalsteamareimportant,forinstanceforlifetimeassessmentofheatexchangersinpowerplants.Additivemanufacturingofmetalresultsinmaterialswithmetastable(highenergy)microstructuresthatwillevolveatelevatedtemperature.TheserepresentareasofpotentialprogramdevelopmentforLANLasawhole.

Agingmeasurementsarecurrentlyperformedbyrepeatedlyplacingandremovingthesampleinthesampleenvironment,inthebeamposition,overthedesiredagingperiod.Thisintroducesbothriskanduncertainty.Thesampleisoftenrequiredtobeheldatanextremetemperature.Movingsuchsampleenvironmentisdifficult,anddisturbingtheenvironmentriskstheintegrityoftheexperiment,potentiallyaftermonthsofintermittentdatacollection.Latticeparametermeasurementswithsufficientaccuracytomonitorchangesinstressand/orsolutechemistryrequirethesampletobepositionedwithsub-mmaccuracy,whichisverydifficultinsideanenvironmentalchamber.Thiscanbemitigatedbyattachingacalibranttothesampleintheenvironment,butthecalibrantmustbefirmlyattachedtothesampleandthecalibrantwillbeexposedtotheenvironment.Theseissuesaddconsiderableuncertaintytomeasurementsattemptingtoaccesschangesinmicrostructure—forinstance,changesinlatticeparameterof100ppm—thatmayoccurovertimeinextremeenvironments.

Theidealsolutionistoleavetheenvironmentalchamberintactatthemeasurementpositionforthedurationofaging.Thiswouldremoveboththeriskofmovingtheequipmentandofchangingtheinstrumentcalibration.Thisrequiresthattheinstrumentbededicatedtothesemeasurements.

Flightpath1(NPDF)iscurrentlydormantandcouldbeoperatedinthismodewithnolossofcapacity,andinitially,verylittleinvestment.Theabilitytocarryoutlong-termneutronscatteringmeasurementsovermanyweekswouldbeuniqueintheworld.Thiswouldrequireasmallinvestmenttoincreasetheoperatingbudgetsfor

Figure5.Williamson-HallplotfromaPu-2wt%Gasampleafteragingat<50Kforfourmonths(green)andsubsequentannealing(pink)at673Kfor48hours.Thereducedslopeindicated5xreductionofthedislocationdensityinthematerial.

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PhysicsandMaterialsScienceandTechnologydivisions,byabout0.3FTEeachtoprovidetechnicalandscientificsupport.ThiswouldallowmeasurementsonPuorU6Nbattemperature.

Significantadvancesinscopecouldberealizedbydevelopingmulti-modalmeasurementcapabilitiesunderrelevantenvironmentsforabout$1.5M.Thisinvestmentincludesextremetemperature(10K-1200K)andchemicalexposuresampleenvironments,small-anglescatteringcapability,andapositioningsystem.Furtherimprovementintimeresolutioncouldberealizedwiththeinstallationofaneutronguidesystemonflightpath1(NPDF),whichwouldleadtoa5-foldincreaseintheneutronflux.

ISOTOPEPRODUCTIONATLANSCE

TheIsotopeProductionProgramhasbeenproducingradioisotopesatLANSCEformorethanfourdecadestomeetdomesticandinternationalneedfortheseproducts.Historicalproductionactivitiesusedthe800-MeVprotonbeamatthebeamstopatAreaA,butthisactivitywasdiscontinuedinthelate1990s.WhiledispensingofisotopeinventoryandprocessingofirradiatedtargetscontinuedatLANL,therewasaclearneedtoreestablishadedicatedirradiationfacilitytoproduceisotopesthatwereotherwisecommerciallyunavailableordifficulttoproduceintherequiredquantities.Amulti-yeareffortwasundertakentoconstructtheIsotopeProductionFacility,whichwascommissionedin2004.IPFwasbuilttoaccept100-MeVprotonbeam,whichisdivertedfromthemainaxisatthetransitionregionafterthe201linac,takingadvantageofthehigherpurityofisotopesthatcanbeproducedatthisintermediateenergy.

Theisotopeprogram’smainfocustodayistoproduceisotopesformedicaluse,primarilystrontium-82forcardiacimagingandgermanium-68forcancerandotherdiseaseimaging.IsotopesproducedatLANLimpacttensofthousandsofpatientseachmonth.Theprogrammakesavarietyofotherisotopesformedical,industrial,andenvironmentalapplicationsandnuclearphysicsresearch,currentlyaveragingmorethan200shipmentsayeartocustomersaroundtheworld.In2009,theisotopeprogrammovedintotheU.S.DepartmentofEnergy,OfficeofScience,OfficeofNuclearPhysics(NP).Thesponsordirectsarobustproductionandresearchmissiontomeettheneedsoftheisotopeusercommunity.WhileIPFisnotauserfacility,researchisveryimportanttothesponsorandcanbeconductedatIPFaslongasithasnonegativeimpacttotheproductionmission.

TomaintainLANL’spositionofleadershipindomesticaccelerator-basedisotopeproduction,tomeetclinicalneedsforemergingmedicalisotopes,andtocontinueastrongresearchprogramintodevelopingnewisotopeproductsforthefuture,theIsotopeProductionProgramhasseveralprioritiesforinvestment.

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PROCESSINGCAPABILITYFORALPHA-EMITTINGISOTOPES

LANL’sIsotopeProductionProgramhasbeguntoexploreaccelerator-basedproductionofactinium-225,anisotopeshowinggreatpromiseforcancertherapy.Whilesmallclinicaltrialsindicategreatpotential,broadclinicaluseofthisisotopewillnotbecomearealitywithoutasignificantincreaseinavailableandreliablesupply.Toaddressthisneed,NPinitiatedaprojectin2015betweenLANL,BrookhavenNationalLaboratory,andOakRidgeNationalLaboratorytopursuereliableproduction.LANLhasdemonstratedcapabilitytoproduce>100mCiamountsthroughirradiationofthoriumtargetsatIPF.Althoughsometechnicalhurdlesremain,furtherscale-upoftheirradiationtogenerate>1CurieamountsinasingletargetatIPFisfeasible.ProcessingthesetargetstoisolatetheAc-225productremainsasignificantchallenge.LANLhasnofacilitywithappropriateinfrastructurecapableofconductingtheseparationoftheAc-225fromtheirradiatedThtarget.Thehigh-levelrequirementisarobusthotcellbank,withsubstantialshieldingaswellasappropriatecontainmentforalphaemitters,locatedinafacilitywithauthorizationbasistoworkwith>hazardcategory3levelsofradioactivematerials.Thefacilitymusthaveassociatedradiologicallaboratoryspacetosupportanalyticalandshippingwork.ThefacilitymustmeetthequalityrequirementsoftheU.S.FoodandDrugAdministrationfortheproductionofaproductintendedforeventualuseinhumans.

TheAreaAhotcellsaretheonlycurrentlyavailableoptiontopursuethisradiochemicalprocessingatLANL.Theexistinghotcellbankhasbeenoutofserviceforovertwodecades,butthegeneralinfrastructurewouldbesufficient.EstablishingprocessingcapabilityatLANL,coupledincloseproximitytotherobustirradiationcapabilityofIPF,wouldestablishLANLasaworldleaderfortheproductionofAc-225.Preliminaryestimatestoreturnthehotcellstoserviceareontheorderof$20M.AproposalwillshortlybesubmittedtoNPtobeginengineeringdesignoftheventilationandotherinfrastructureupgradesthatwillberequiredfortheAreaAhotcells,witharefinedcostestimateforthework.

TheageoftheAreaAhotcellsandtheircurrentconditionmayindicatethatanewhotcellcapabilitymaybeamorecost-effectivesolutionthantherefurbishmentoftheexistinghotcells.Therefore,theestablishmentofastand-alonehotcellcapabilitywillalsobeexplored.Afollow-onproposaltobeginrefurbishmentornewconstructionworkwillbesubmittedafterthecostsarebetterdefinedandonatimelinematchingcustomerdemand.ThehighestpriorityneedfortheIsotopeProductionProgramistoobtainhotcellspaceappropriatefortheprocessingofirradiatedthoriumtargetsfromIPFfortheisolationofCuriescalequantitiesofAc-225.

INCREASEDCURRENTFORENHANCEDPRODUCTION

ThesecondprioritywouldbetoincreasethecurrentthatIPFcanacceptforroutineandresearchirradiations.Highercurrentenablesincreasedproductioncapacity.Atthistime,IPFoperatesat230 µAforroutineirradiations,whichisdrivenprimarilybylimitationson

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thetargetdesignforastandardRbCltargetirradiatedtoproduceSr-82.TherecentlycompletedAcceleratorImprovementProjectatIPFhasaddedtheabilitytochangetheaperturesizeofthebeamstrikeareaandenabledmorecomplexrasterpatternsthatareanticipatedtoallowthesetargetstowithstandmuchhighercurrents.ArecentdemonstrationexperimentsuccessfullyexposedRbCltargetsto320μAofbeam,withacorresponding40%increaseinproduction.

Intheshortterm,thefocuswillbeonremovingadministrativelimitstoincreasethemaximumpossiblebeamcurrentfrom360to450 µA.Thisrequiresachangetothecurrentlimitersettingsthatshouldberelativelystraightforwardtoaccomplishwithminimuminvestment.Inthelongerterm,theprogramrequires~1mAcurrenttoIPF.Thiswouldrequireanassessmentoftheadequacyofthetargetcoolingsystem.ArequesthasbeensubmittedtoDOENPtosupportapreliminaryanalysisofthecoolingwatersystemtodeterminethelimitationsofthecurrentframework.Modelingwillberequiredtounderstandifboilingisoccurringinthecoolingwaterchannelsandtoinformanimproveddesignofthecoolingwatersystem.Thiswouldrequireamodestinvestment(~$400K)inmodelinginfrastructureandabeamwindowandtargetcoolingtestlaboratoryfortheofflinestudyofthermalperformanceandboiling.Furthertestinganddemonstrationwouldberequiredtoensurethathighcurrentoperationistransparenttootherusers.

ADDITIONALHOTCELLPROCESSINGCAPABILITY

TheprogramwillcontinuetoproduceisotopesfornucleardataandtoperformR&Dintotheproductionofotheralpha-emittingisotopesformedicalapplications.Inthepast,theisotopeprogramhasproducedisotopesincludingLu-173andAs-73atIPFandmanufacturedtargetsfromthesematerialstobeusedforneutroncross-sectionmeasurementsatDANCE.WhilesomeisotopescanbehandledattheexistingprocessingfacilityatTA-48,additionalhotcellandradiologicalhoodspaceisneededforthehandlingofirradiatedactinidetargetsfromIPFandthefabricationofactinideorotherradioactivetargetsforotherendusers.Inparticular,thiscapabilitywouldbenefitproposednuclearphysicsexperimentsatLENZ(As-73,74)andDICER(Y-88),whereIPFisuniquelysuitedtomakelargequantitiesoftheseshort-livedisotopes. Aseparatehotcellwouldallowalargersuiteofisotopestobeproducedandallowhigheractivitytargetsofactinidestobesafelyhandled.Procurementofastandalonehotcellandassociatedshieldedhoodis~$400K(unburdened).Ventilationtosupportthehotcellcouldcostanadditional~$1M,dependingonlocationandthelevelofexistinginfrastructureinthespace.AnalternativesanalysiswasperformedbytheprograminFY17,identifyingseveralpotentiallocationsforthesitingofsuchahotcellandtheprosandconsofeachlocation.Afinaldecisionbymanagementforspaceisstillpending.Supportwouldbeneededtoprocureandinstallthehotcell,hood,andassociatedventilationonceafinaldeterminationforlocationismade.Thisactivitycouldbecombinedwiththealphaprocessingcapabilitydependingonlocation.

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RETURNOFSPALLATIONPRODUCTIONCAPABILITYTOAREAA

Along-termgoalistoreestablishspallationproductioncapabilityatAreaA.Thiscapabilityisrequiredtoproducecertainradionuclidesthatarenotaccessibleatthelowerenergyprotonirradiationfacilities(100MeVforIPFor200MeVatBrookhavenLinacIsotopeProducer(BLIP),andtoincreasecapacityforhighpriorityisotopessuchasAc-225.Inadditiontore-establishingbeamdeliverytoAreaA,thiswouldrequireanewtargetirradiationstationtobebuiltatAreaAtoacceptthehighenergy,highcurrentbeam,estimatedinthe$20-30Mrange.

ESTABLISHAMATERIALSSURVIVABILITYLABORATORY

MaterialresponsetoradiationinsultsisanareaofinteresttoNNSA,thenuclearenergyprogram,andelectronicsmanufacturers.

1. NNSA’sinterestsincludematerialresponsetohostileenvironments,changesinmaterialperformanceduetoradiationdamage,radiationeffectsonelectronics,andtheeffectsofself-inducedradiationdamageinplutonium.AmoredetaileddescriptionofNNSAneedsisgivenintheclassifiedappendix.

2. Fastnuclearreactorsproducelesshigh-levelwastewhilemoreefficientlyburningnuclearfuel.LANSCEwastheproposedsitefortheMaterialTestStation,whichwouldhavequalifiedfuelsforfastreactorsinaspallationproducedfastneutronspectrum,similartothatexperiencedinafastreactor.

3. Electronicsdeployedinspacearesubjecttoprotonirradiationinearthorbitandindeepspace.Understandingandmitigatingtheeffectsofthisradiationisnecessarytoensuresuccessfulspace-basedmissions.

TheestablishmentofaMaterialsSurvivabilityLaboratoryatLANSCEwouldaddressallthreeneedsandcouldbeimplementedinaphasedapproachovera10-yearperiod.AreaAatLANSCEisanaturallocationforsuchafacility.Theacceleratorhastheabilitytodeliver1MWof800-MeVprotonstothearea,thereis10MWofelectricalpoweravailable,30,000ft2offloorspace,andtwounusedhotcellsinAreaA.Weproposeathree-stagedevelopmentoftheMaterialsSurvivabilityLaboratory,withthestagesdefinedbythebeampowerrequirementsandfacilitycomplexity.

1. Stage1.Low-powerprotonsource(LPPS)forspace-electronicsirradiation.Thiswouldrequire100nAofpowerdeliveredtoAreaAwithasmallflightpath,withminimalshieldingrequirements.

2. Stage2.Moderate-powerfacilitywithneutronspallationtargettostudyplutoniumaging.Thiswouldrequire100μAofbeampower,aneutronspallationtarget,andbasicinsitudiagnosticcapability.

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3. Stage3.High-powerfacilityfortestingnuclearfuels.ThisfacilitywouldalsobecapableofproducingAc-225inclinincallyrelevantquantities.Thiswouldrequire1mAofbeampowerdeliveredtoAreaAandasubstantialamountofshielding.

LOW-POWERPROTONSOURCE

TheLPPSwouldservethespaceelectronicscommunityfortestingthesusceptibilityofsatelliteandextra-terrestrialcomponentstoproton-inducedsingle-eventupsetsinthesamewaythatWNRservestheaviationelectronicsindustryusingneutrons.PotentialcustomersforsuchafacilityarenonproliferationprogramsinNNSA’sNA-22,theNationalReconnaissanceOffice(NRO),NASA,NationalOceanicandAtmosphericAdministration(NOAA),andindustry.TheLPPSwouldsupplantacapabilitylosttothespaceelectronics

communitywiththerecentclosure(in2014)oftheIndianaUniversityCyclotronFacility’sRadiationEffectsResearchStation5.Thatfacilitydelivered30-to200-MeVprotonswith50-nAbeamcurrentandbeamspotsizerangingfrom2to30cmindiameter.TheAreaAfacilitycoulddeliver100nAof800-MeVprotonstousers.Withsomemodificationoftheswitchyardbeamline,beamenergiesaslowas200MeVcouldbedeliveredtoAreaA,withoutanyimpactonbeamdeliverytoexistingLANSCEfacilities.The120-HzprotonbeamrepetitionratewouldneedtobesharedbetweenIPFandAreaA,withIPFreceivingupto30Hz(limitedbytheIPFfastkicker)andAreaAreceivingtheremainderofthepulses(at

5B.VonPrzewoski,etal.,MRSSymp.Proc.851NN7.10.1(2005).

Figure6.PossiblelayoutofAreaA.

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least90Hz).ThereissubstantialinterestwithinthespaceradiationeffectscommunityfortherealizationoftheLPPS.BothIntelandSpaceXhavewrittenlettersofsupportforthefacility,eachpredictinghundredsofhoursperyearofbeamtimeuse.

MODERATE-POWERNEUTRONSPALLATIONSOURCE

Themoderate-powerstationwouldbeusedfortestingthesurvivabilityofmaterialstointenseneutronradiation,inparticulartostudyfission-induceddamageandheatinginfissilematerials.Thiswouldprimarilyservetheweaponscommunity.Aproton-drivenspallationtargetwouldcreateanintensesourceofpulsed,moderatedneutrons,withpulsewidthstunablefromsub-µsto625µs.Aprotonbeamcurrentofupto100µAwillproducesufficientlyintenseneutronpulsesforthismission.Furtherdetailsareprovidedinaclassifiedaddendumtothisreport.

HIGH-POWERFASTNEUTRONSPALLATIONSOURCE

Onadecadaltimescale,athird,high-powerirradiationstationisenvisagedthatcanservemultiplemissionsfrommedicalisotopeproductiontotestingnuclearfuelforthenextgenerationoffastreactors.Thisstationwouldusethefull1-mAcapabilityoftheLANSCElinac,deliveredtoaspallationtargettoproduceanintensesourceofneutronsexceeding1014ncm–2s–1neutronflux.TheoriginalLosAlamosMesonPhysicsFacilityA6targetprovidedthemedicalcommunitywithspallation-producedisotopesfordecades.Re-establishmentofan800-MeVisotopeproductioncapabilitywouldcomplementtheIPFcapability,deliveringdifferentisotopes,includingAc-225.SuchatargetcouldevendeliverasignificantfractionofthecurrentU.S.demandforMo-99,themostcommonlyusedmedicalisotope6.Spallationsourcesarewellsuitedforirradiationtestingoffirst-wallmaterialsforfusionsystems7.At1mAofbeamcurrentthisfacilitywouldprovideatestingcapabilityforthefusionmaterialscommunity,deliveringadamagerateinironupto10atomicdisplacementsperyearconcurrentwithprototypicheliumproductionrates.AreaAiswellsuitedforhousinganaccelerator-drivenneutronsourceforsmall-scalefastreactorfueltesting8.Multiplefuelrodletsupto20cminlengthcanbeirradiatedsimultaneouslyinafastneutronspectrumapproaching1015ncm–2s–1.

BeamdeliverytoAreaAwillrequireanupdateoftheLANSCESafetyAssessmentDocumentandtheAcceleratorSafetyEnvelopeandapprovalbytheLosAlamosFieldOffice.

6E.J.Pitcher,ProceedingsoftheInternationalTopicalMeetingonNuclearResearchApplicationsand

UtilizationofAccelerators2009,Vienna,LA-UR-09-04276.7E.J.Pitcher,C.T.KelseyIV,S.A.Maloy,FusionScienceandTechnology62,289-294(2012).8E.J.Pitcher,JournalofNuclearMaterials37717-20(2008).

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ULTRACOLDNEUTRONFACILITY

TherecentupgradeoftheLANLUltracoldNeutronFacilitymorethantripledthepreviousoutput(Figure6)andhascreatedanopportunityforworld-classprecisionneutronmeasurementstoprobethefundamentalsymmetriesofnature9.Overthenext10yearsweproposetodevelop,build,andoperatethreenext-generationexperimentsto:

1. searchfortheneutronpermanentelectricdipolemoment(EDM)atthelevelof10-27e·cm(a10-foldimprovementoverthecurrentstateoftheart);

2. measurethebetaasymmetryinpolarizedneutrondecayatthe0.2%level(3-foldimprovementoverthestateoftheart);and

3. measuretheneutronlifetimetobelow0.1secondprecisionaftercompletingrunningofthecurrentUCNtexperiment.

Fortheseeffortstoremaincompetitivewewillcontinuetoimprovetheultracoldneutronsourceandfacility.

WhiletheStandardModel(SM)offundamentalinteractionsprovidesaremarkablygooddescriptionofnatureuptoenergiesoforder200GeV,fundamentalobservationssuchasthematter-antimatterasymmetryanddarkmatterremainunexplained.Theseobservationsandtheoreticalconsiderationspointtotheexistenceofnewinteractionsanddegreesoffreedom.InlightofnullresultsfromsearchesfornewphysicsattheLargeHadronCollider,low-energyprecisionmeasurementsprovideimportantinputtothesymmetrystructureoftheuniversebeyondtheSM(BSM).Inthiscontext,neutronphysicsoffersopportunitiestoprobenewinteractions.Theabove-mentionedprogramisalignedwiththeNuclearScienceAdvisoryCommittee2015LongRangePlanforNuclearScience10,whichincludespursuinga“targetedprogramoffundamentalsymmetriesandneutrinoresearchthatopensnewdoorstophysicsbeyondtheStandardModel.”

NEUTRONELECTRIC-DIPOLEMOMENTEXPERIMENT

Searchesforanon-zeroneutronelectric-dipolemoment(EDM)probenewsourcesoftimereversalsymmetryviolationandmaygiveinsightintothematter-antimatterasymmetryintheuniverse.Thecurrentupperlimit,setbyanexperimentperformedmorethanadecadeagoattheInstitutLaueLangevinturbineultracoldneutronsource,isdn<3.0×10−26e·cm(90%C.L.)11.Furtherimprovementinthesensitivityofexperimentshasbeenhamperedbythelackofsufficientlystrongsourcesofultracoldneutrons.Ithasbeenshownthatsystematiceffectscanbecontrolledtothelevelnecessary.Ourrecentwork10hasshown

9T.M.Ito,etal.,toappearinPhys.Rev.C,arXiv:1710.05182(2018).10A.Aprahamian,etal.,“Reachingforthehorizon:The2015longrangeplanfornuclearscience''(2015).11C.A.Baker,etal.,Phys.Rev.Lett.97,131801(2006).

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thatonecanperformaroomtemperatureneutronEDMexperiment(withLANL’sultracoldneutronsource)basedonRamsey’sseparatedoscillatoryfieldmethodwithaone-standard-deviationsensitivityofσ(dn)=3×10−27e·cmwitharunningtimeoffivecalendaryears.TheLANLneutronEDMcollaborationhasrecentlyconstructedademonstrationapparatuswithwhichaneutronmagneticresonancemeasurementbasedonRamsey’sseparatedoscillatoryfieldmethodwasdemonstrated.

UCNA+EXPERIMENT

IntheUCNA+experiment,weproposetodevelopthehighestprecisionultracoldneutron-basedmeasurementofthenucleonaxialchargegA.ThiscombinedwiththemeasurementoftheneutronlifetimedescribedbelowwillallowanimproveddeterminationofVudwithoutthecontroversialnuclearcorrectionsrequiredfortheanalysisof0+_>0+nuclearbetadecaytransitions.SeveralworldwideeffortsaimtomeasuregAtoincreasedprecisionoverthestateoftheartestablishedbyPERKEOII12andLANL’sUCNA13.LANL’seffortstandsoutbecauseallothercurrenteffortsplantousecoldneutronbeamsandthussharemanyinherentsystematicuncertainties.

ThepreviousUCNAexperimentwaslimitedbythelackofstatistics(duetotherelativelylowdensityofavailableultracoldneutrons)andbysystematicuncertaintiescausedbythenonlinearenergyresponseofthebetaparticledetectorsystems,whichconsistedofthin-windowedmultiwireproportionalchambersinfrontofplasticscintillators.Withtheupgradedultracoldneutronsource,wehavemeasuredatotalbetadecayrateof250HzintheUCNAdecayvolume,anearly10-foldimprovementoverthetypicaldecayratesobservedduringtheUCNArun.Thisimprovedrate,whichiscomparabletothatofcoldneutronbeambasedexperiments,willprovidesufficientstatistics.SincetheconstructionofUCNAin2005,particledetectortechnologieshaveadvanced,enablingustodevelopnewelectrondetectorsystems,withwell-characterizedenergyresponse.Weareinvestigatingtheuseofmagneticfieldinsensitivedetectorssuchassiliconphotomultipliers(SiPMs)toeliminatethelighttransferproblemsoftheUCNAdetectorsystem.

NEUTRONLIFETIMEEXPERIMENT

Withthepublicationofthe2016datasettheUCNtexperimenthasreachedtheprecisionofthemostsensitivemeasurementoftheneutronlifetime14thisyearthestatisticallimithasbeenpusheddowntobelow0.3secondsanditcurrentlylooksliketheexperimenthasthreemoreyearsofrunningtoreachatotaluncertaintyoflessthan0.2seconds.Thisworkisleadingtoaconceptforanewapparatusthatcanreachaprecisionbelow0.1seconds;thedevelopmentofthisexperimentwilltakeseveralyearsafterthecompletionofUCNt.

12D.Mund,etal.,Phys.Rev.Lett.,110,172502(2013).13B.Plaster,etal.,Phys.Rev.C86,055501(2012)andM.A.P.Brown,etal.,arXiv:1712.0088414R.W.Patti,etal.,toappearinScience,(2018)arXiv:1707.01817

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NEUTRONSOURCEDEVELOPMENT

Alloftheproposedexperimentsareratelimitedandbenefitfromcontinuedimprovementstotheultracoldneutronsourcedensityandbeamavailability.Ultracoldneutrondensityinthesourceandinexperimentscanbeincreasedbymoreintenseprotonbeamdelivery(theaveragecurrentislimitedto10uA).Thiscanbeachievedbyincreasingthefrequencyofprotonpulsestothetargetabovethecurrent20Hz.ThiswillrequiresomeacceleratorR&Dandtheadditionofafastkickermagnet.Additionally,thetungstentargetmayneedredesign.TheinstallationofashieldwallbetweenpRadandUCNbeamlineswillincreaseoverallstatisticsinexperimentsbyallowingfordaytimerunningofUCN.Thiscouldbefurtherimprovedwiththedevelopmentofafastacceleratortunechangebetweenthebeamlines.Theseimprovementswouldleadtoafactorof~2increaseinstatistics.Additionalsmallgainsmaybepossiblebyredesigningthecurrent10-uAultracoldneutronsource,buttomakesubstantialincreasesinUCNproductionahighercurrentdeuteriumorliquidheliumsourceisneeded15.

TherearesynergiesbetweentheseexperimentsandotherscurrentlyunderdevelopmentbytheDOEandNationalScienceFoundation.CarryingoutaroomtemperaturemeasurementoftheneutronEDMwillfacilitatedevelopmentoftechniques,expertise,andscientistsneededtosuccessfullycompletetheSpallationNeutronSource(SNS)-basedneutronEDMproject.Boththeeffortsofthebeamlifetimeexperiment(coldneutrons)andUCNt(ultracoldneutrons)areneededtomoveforwardontheneutronlifetimemeasurement;eachhavingsignificantlydifferentsystematicserrors.ThemeasurementsofUCNA+andNabcaneachbecombinedwiththeneutronlifetimetocalculateavalueforthequarkmixingmatrixelementVud,buttheyhaveverydifferentsystematicerrors,whichisvaluableingainingconfidenceinhighprecisionbetadecaymeasurementsalreadydemonstratedbythepairingofPERKEOIIandUCNA.

Thecurrentplanforcarryingoutthesethreeexperimentswilltakeusbeyondthenext10years.ThecurrentUCNtexperimentwillrunforthenextthreeyearsstudyingsystematicsandgatheringstatistics.Afterthisdevelopment,funding,constructionandrunningofanext-generationneutronlifetimeexperimentwillcontinuepasttheendofthis10-yearplan.Ascurrentlyenvisioned,UCNA+willrequireayearofR&Dandconstructionfollowedbytwoyearsofcommissioningandrunning.Afterthis,otherpolarizedbetadecaycorrelationsmaybepursued.ThecapitalinvestmentissmallandR&Dhasalreadybegun,soUCNA+couldbecompletedinthefirstfiveyears.ThebuildingandcommissioningofanEDMexperimentwilltakethreeyears.Anadditionalfiveyearsofdatatakingisrequiredtoachieveoursensitivitygoals.

15A.R.Young,etal.PhysicsProcedia51(2014).

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Inadditiontoourthreemainthrusts,thereareothereffortsthatmakeuseofthefacility;theseactivitiesaresponsoredbyexternalcollaborators.TheSNSneutronEDMprogramhasusedthewestbeamlinetoperformR&Donitscryogenicstoragecellandwillcontinuethiseffortforseveralyears.ThedetectorsanddataacquisitionsystemfortheSNSNabexperimentcontinuetobedevelopedusingthelargespectrometer.Othersmallereffortsaredoneparasiticallywhilethemainexperimentsarerunningwithminimalimpactonourmainefforts:fission,gravity,darkmatter,detectordevelopment,nuclearbetaspectroscopy,andquantuminformationscience.

Figure6.ThedensityofultracoldneutronsproducedbytheLANLUltracoldNeutronFacilityfrom2004to2016.

ACCELERATORIMPROVEMENTS

TheLANSCEacceleratorwascommissionedin1972.Despitetheageoftheacceleratoritisstilloneofthemorepowerfulprotonlinacsintheworld,capableofgenerating1MWofpowerinan800-MeVprotonbeam.Thereplacementvalueofthelinacisestimatedtobeover$1Bandformanyyearsrequiredmaintenancehadbeendeferred.ALANSCERiskMitigation(LRM)activitywasundertaken,beginningin2009andendingin2015.Roughly$140Mwasspentduringthisperiodtoaddresslong-termmaintenanceissuesandensurethattheacceleratorcould,withcontinuedinvestment,continuetooperateintotheforeseeablefuture.TheLRMactivityreplacedthreeofthefourhigh-powerRFamplifiersinthe201-MHzdrift-tubelinac,purchasedreplacementklystronsforthe805-MHzcoupled-celllinac,madeprogressontheupgradeoftheagingcontrolsanddiagnosticssystems,installedamoderntimingsystem,implementedadigitallow-levelRFsystemforthedrift-tubelinac,upgradedmanymagnetpowersuppliesandvacuumsystems,andgenerallyreplacedobsoletepartswithmoderncomponentswheneverpossible.Thecompletionofthe

31

LRMactivityenabledthereturnto120-Hzoperation,effectivelydoublingthebeamcurrentandprovidedsignificantlymorestableoperations.

ToachieveLANSCE’smissionitisimperativethattheacceleratorbeabletorunreliably,withhighavailability(toenablerobustexperimentscheduling)andstablebeams(toensurestableexperimentalconditions).Toaccomplishthesegoalsthetopthreeprioritiesfortheacceleratorareto

1. modernizethediagnosticandcontrolsystems,2. improvetheperformanceandlifetimeoftheH-source,and3. completetheinstallationofthedigitallow-levelRF(dLLRF)system.

Longertermprioritizedgoalsareto

1. replacethe201-MHzModule1RFsystemwithitsmoderncounterpart,2. reestablishbeamdeliverytoAreaA,3. improvetheperformanceoftheprotonstoragering,4. replacetheCockroft-Waltonwitharadio-frequencyquadrupolefortheH+source,and5. upgradethewaterdistributionsystemontheremainingthreedrift-tubelinacs(DTLs).

Thesearediscussedinmoredetailbelow.

MODERNIZETHEDIAGNOSTICANDCONTROLSYSTEMS

ThepresentLANSCElinacdiagnosticsandcontrolsystemcombinesobsolete1980’scomputertechnologyand1960’sin-housefabricatedremoteindicationandcontrolequipment,withapartially-implemented,modernExperimentalPhysicsandIndustrialControlSystem(EPICS)-basedcontrolsystemandnewbeamdiagnostics.Componentsofthesesystemsincludethebeampositionandphasemeasurement(BPPM)system,industrialcontrols(hardwareandsoftware),thetimingsystem,theacceleratorfast-protectsystem,thetimed-datasystem,andbeammeasurementdevicessuchaswirescanners,harps,andemittancegear.Manyofthesesystemscommunicateusinganobsoletecomputernetworksystemwithinsufficientbandwidthtohandlemoderndatatransferneeds.Modernizationofthediagnosticsandcontrolsystemwithmoderncomputertechnologyandmodular,scalable,andupgradablecommercialoff-the-shelfcomponentswillallowforaflexibleevent-basedtimingsystemandimplementahigh-speed,high-capacitynetworkinfrastructure.

Currently,machinetuningcantakedaysandsomeproblemshavetakenweekstodiagnoseandcorrect.InteractivemachinesimulationcodesbasedonfastGPUprocessorshavebeendevelopedthatshouldenableamoreautomatedapproachtotuninganddiagnosis.Theupgradeofthediagnosticsandcontrolsystemwillenableustofurtherexploitthiscapability.Thegoalistocombinetheupgradeddiagnosticandcontrolsystemwith

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proceduresthatautomatemanyprocessestoenhanceoverallbeamtuningandcontrol.Theseprocedureswillincorporatemachine-learningalgorithmstoenhancecomplexmachinetuningordinarilycarriedoutbyexperts,toenablearobustandfastacceleratortuning.

Todatethetotalinvestmentincontrolsanddiagnosticsupgradesis$29M.Theestimatedremainingcosttocompleteis$12.5M.Oftheestimated$12.5Mremainingcost,$7.2MisscopebeyondwhatwasplannedduringtheLRMactivity.Theestimatedtimetocompleteallremainingtasksis2.5to4yearsbasedonfundingprofileandabilitytoexecutescopewithoutsignificantlyimpactingtheLANSCEoperatingschedule.

IMPROVEMENTSTOTHEH-SOURCEANDMULTI-BEAMOPERATIONS

ThecurrentH-sourcehasalifetimeofroughly28daysdelivering16-mA,350-nspulsesat120Hz.Otherfacilities,withmoremodernsources,havedemonstratedlongersourcelifetimeswithhighercurrentsforlong-pulseoperation(highdutyfactor).ThefirstneedforincreasedcurrentistheneutrondiffractionworkattheLujanCenter.Thenewtarget(2020installation)willresultina25%reductioninneutronfluxtothematerialscienceflightpaths.AnincreaseintheH-currentcancompensateforthisreduction,restoring(andevenimprovingupon)thecurrentcapabilityofthematerialscienceprogram.Fartherintothefuture,asecondaxisoranachromaticlensatpRadwillneedincreasedcurrenttoobtainoptimalperformance.AtUCNandWNRanincreaseincurrentwillleadtoaproportionalreductioninthetimeneededtocompleteanexperiment.

Incrementalincreasesinperformancemaybepossiblebymodifyingtheexistingsource,however,significantincreasesinoutputcurrentandsourcelifetimewillrequireanewtypeofsource.OnealternativeistheSpallationNeutronSourceexternalantenna,RF-driven,multi-cusp,cesium-enhancedH-ionsource.Thissourcehasdemonstratedalifetimeinexcessof50daysandoutputcurrenttogroundof40mA.Itisestimatedthatdesign,fabrication,andimplementationofanewH-sourcewillrangefrom$500K-$1,000K.

Anotherapproachtoincreasingbeamcurrentistoinstallade-bunchercavityintheH-transportlineupstreamofthemainbuncher.Currently,thetwoLANSCEbeams(H+andH-)arecombinedinacommontransportsystemupstreamofthelinac,whichcontainsamainbunchercavity,ofwhichthephaseandamplitudesettingsareacompromiseforthetwobeams.Installationofade-bunchercavityintheH-transportlineupstreamofthemainbuncherwoulddecouplethetwo-beambunchingandcapture.ImplementationcouldimprovethepeakbeamcurrentdeliveredtoWNRandpRadbyupto50%.Thisrequiresfabricationandinstallationofacompact201.25-MHz,quarter-wavecavityandprocurementandinstallationofalow-powerRFsystem(includingcontrols).Theestimatedcostis$400K.Additionalimprovementsinmulti-beamoperationscanberealizedbyimprovingtheH-chopperrisetimeandphasecontrolatanestimatedcostof$100K.

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COMPLETETHEINSTALLATIONOFTHEDIGITALLOW-LEVELRFSYSTEM

TherearetwomajorRFsystemspoweringthe800-MeVprotonlinac,oneoperatingat201.25MHzandoneatthefourthharmonic,805MHz.The201.25-MHzsystempowersthefourDTLacceleratingstructures(RFModules1-4),whilethe805-MHzsystempowerstheremaining104CCLacceleratingstructures(RFModules5-48).IntheDTL,eachacceleratingstructureisdrivenbyitsownhigh-powerRFsource.IntheCCL,fouracceleratingstructuresarepoweredbyasingleklystronuptoabeamenergyof211MeV(RFModule12).BeyondthispointintheCCLtheacceleratingcavitylengthisdoubled,requiringasingleklystronRFsourcepertwoCCLcavitiesupto800MeV(RFModules13-48).Allofthesehigh-powerRFsourcesrequirestablephaseandamplitudecontrol(typically<0.1°inphaseand<0.1%inamplitude)tomaintainlowbeamlossesinthestructuresforhands-onmaintainability.Inaddition,suchstabilitymustbeaccomplishedinadynamicenvironmentwherevariousbeampatternscreatetime-varyingloadsthattheRFsystemmustaccommodateonapulse-by-pulsebasis,whileslowvariations,suchastemperature,thatimpactthestructuretuningmustbealsobecorrected.Controloftheresponseofthehigh-powerRFsystemstothesetime-varyingloadsisachievedthroughthelow-levelRF(LLRF)system,whichusesappropriatelyplacedRFsensorsthroughoutthelinactogeneratesignalsusedtomaketheadjustmentsnecessarytomaintaintheRFphasesandamplitudestowithinthedesiredtolerances.

Aswithmanyothermajorsystemsonthelinac,theLLRFsystemwasdesigned,constructed,andimplementeddecadesagoutilizinganalogcircuitryandmechanicalactuators.Whilethiswasareasonablesolutionfortheoriginalsystem,todayitisobsolete,difficulttomaintain,andlackingfeaturessuchasintegrationwithamoderncontrolsystemsuchasEPICSandthebandwidthnecessarytofullyexploitthepotentialofthemachine.AdvancedLLRFsystemsbasedonmoderndigitaltechnologyarenowusedthroughouttheworld.HereatLANSCEwehavemadesomeprogressimplementingadigitalLLRF(dLLRF)systemfortheentirelinac.Todate,thedLLRFsystemhasbeenimplementedonthreeofthefour201.25MHzDTLs,andasystemhasbeendesignedandtestedontwoofthe40805-MHzCCLmodules.FullimplementationofthedLLRFsystemwillrequireanadditional$3.76Mspreadoverfouryears.

REPLACETHE201-MHZMODULE1RFSYSTEMWITHITSMODERNCOUNTERPART

Asdescribedearlier,theDTLconsistoffouracceleratingstructures,eachwithitsownhigh-powerRFsource(Modules1-4).Modules2through4haveeachhadtheirhigh-powerRFsystemsreplacedwithnew,diacrode-basedsystemsaspartoftheLANSCE-LRMproject.Module1isstilloperatingwiththeoriginalnearly45-year-oldsystemandneedstobeupdated.AlthoughtheRFpowerrequirementforModule1islowerthanthatoftheother

34

DTLRFmodules,thisimprovementwillmakeModule1morereliable,similartoModules2-4,andfullycompatiblewiththeimprovedcontrolanddLLRFsystems.Themodificationwouldtakeapproximatelyfourmonthstocomplete,i.e.,duringthelengthofasingleextendedmaintenanceperiod,andcost$600k.

RE-ESTABLISHBEAMDELIVERYTOAREAA

TheLPPS,theMaterialsSurvivabilityLaboratory,andaprotonradiographysecondstationallrequirethedeliveryofH+beamtoAreaA.InthecaseofLPPS,thebeamenergyshouldbetunablefrom200MeVto800MeV.ThisrequiresbeamsharingwiththeIPF,theonlyotheruseroftheH+beam.Apulsedkickermagnetsystemdrivenbyapulsedmodulatorwasdesignedandbuilt.However,sincetheIPFisthesoleuseroftheH+beam,thissystemwasneverfullycompletedorimplemented.(Themodulatorislockedoutandthekickermagnetispresentlyoperatedindcmode,poweredwithadcpowersupply.)

TodeliverbeamtoAreaAthestainless-steelkickervacuumvesselneedstobereplacedwithanon-metallicvessel(toeliminateunacceptableeddycurrents).Apossiblesolutionistheuseofafusedquartzvacuumvessel,whichmustbedesigned,fabricated,andtested.Theexpectedcostfordevelopmentandimplementationofthevacuumvesselis$250K.Themodulatorsystemmustbetestedandinstalledatanestimatedcostof$200K.Toenablethedeliveryof200-MeVbeamtoAreaA,theswitchyardmustbereconfigured,withalargeaperturemagnetinstalledtoaccepttheH+beamfrom200MeVto800MeV.ToenablethehighercurrentneedsoftheMaterialsSurvivabilityLaboratory,thelinacmustbealignedtoavoidunacceptablebeamlossesandtheconsequentactivationofcomponents.

IMPROVETHEPERFORMANCEOFTHEPROTONSTORAGERING(PSR)

Asshownabove,thenuclearphysicsprogramattheLujanCentercanbenefitsignificantlyfromashorterpulsewidth,wheretheFOMisproportionaltothefluxtimestheinversesquareoftheprotonpulsewidth.WehaverecentlydemonstratedtheabilitytooperatethePSRat30Hzwitha30-nspulsewidth.(ThenominalpulsewidthinthePSRis125ns.)Aninvestmentof$100K-$200KtoincreasethePSRharmonicbunchervoltagefrom15kVtoapproximately25kVwouldfurthershortenthepulsewidthtoapproximately22ns,FWHM.TheFOMfornuclearphysicsexperimentswouldincreasebyafactorof1.8.Significantgainsinshort-pulseintensitywouldrequirealargerinvestmentofapproximately$1M-$2Mtodevelopandimplementabroadband(40-80MHz)RFfeedbacksystemandaddasecondRFgapinthePSR(todampthemicrowaveinstabilitythatlimitsthepulsewidthandintensityofthe30-Hzshort-pulsebeam).Afactorof2increaseinbeamintensity(andFOM)isexpected.ThiswouldbenefitboththematerialscienceandnuclearphysicsprogramsattheLujanCenter.

H+RFQTOREPLACETHECOCKCROFT-WALTON(CW)INJECTOR

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CatastrophicfailureofmajorcomponentsintheCWinjectorcoupledwiththeunavailabilityofsparepartscanleadtosignificantdowntime,perhapseventhelossofanentireruncycle.Toreducethisoperationalrisk,theCWsystemsshouldbereplacedwithmodernRFquadrupole(RFQ)basedinjectors.RFQacceleratorsareemployedworldwideandhavedemonstratedstableandreliableoperation.Tomimicthecurrentpulsestructureandanticipatedmulti-beam-deliveryrequirements,implementationofthree(onefortheH+sourceandtwofortheH-source)RFQ-basedinjectorsarerequired.Eachinjectorisestimatedtocost$14M.Ateststandisbeingassembledtotestanewfour-rod,750-keV,201.25-MHzRFQtoreplacetheH+CWinjector.Theteststandwillincludetheionsource,low-energybeamtransport,RFQ,medium-energybeamtransportdownstreamoftheRFQ,anddiagnosticsneededtoinjectbeamintotheLANSCEdrifttubelinac.

UPGRADETHEWATERDISTRIBUTIONSYSTEMONTHEREMAINING3DTLS

PastdeferredmaintenancetocriticalwatervalvesontheDTLwaterdistributionsystemsledtoearlyfailureofthewaterdistributionsystemoftheModule2DTLandamany-monthdowntimetoimplementtherepair.Therepairwasatemporaryfixwithoneaspectbeingtoreversetheflowofwaterinthesystemtominimizeongoingerosionwithinthecoolingpassages.Afullrepairwasimplementedafewyearsago;however,itissuspectedthattheotherthreeDTLtankshavealsosufferedsimilardamagebuthavenotyetcatastrophicallyruptured.WeneedtoupgradethewaterdistributionsystemstoModules1,3,and4.Thecostforthisisestimatedtobe$4.84M.

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lansce.lanl.gov LA-UR-18-20953