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The NuMI eux000Bx000Cx000E x000Feam
The NuMI eux000Bx000Cx000E x000Feam

The NuMI eux000Bx000Cx000E x000Feam - Description


0x001F NMx001BNHy x001C7930x001Fx000F uh10x000F101x001Fjx000FMhx000BNx000Fx001C015x000F0x000F0x001F3x000Fuh10x000F101x001Fjx000FMhx000BNx000Fx001C015x000F0x000F0x001F3arXiv150706690v2 physicsacc ID: 870843 Download Pdf

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1 The NuMI eu  &
The NuMI eu  eam ,0 -.NMNHy/: 79–30 uh:10101/jMh N0150,03 uh:10101/jMh N0150,03 arXiv:1507.06690v2 [physics.acc-ph] 29 Jul 2015 dFermiNationalAcceleratorLaboratory,Batavia,Illinois60510,USAeRutherfordAppletonLaboratory,ScienceandTechnologiesFacilitiesCouncil,Didcot,OX110QX,UnitedKingdomfDepartmentofPhysicsandAstronomy,UniversityCollegeLondon,GowerStreet,LondonWC1E6B

2 T,UnitedKingdomgLauritsenLaboratory,Cali
T,UnitedKingdomgLauritsenLaboratory,CaliforniaInstituteofTechnology,Pasadena,California91125,USAhDepartmentofPhysicsandAstronomy,UniversityofAlabama,Tuscaloosa,Alabama35487,USAiArgonneNationalLaboratory,Argonne,Illinois60439,USAjDepartmentofPhysics,UniversityofAthens,GR-15771Athens,GreecekDepartmentofPhysics,NationalTech.UniversityofAthens,GR-15780Athens,GreecelPhysicsDepartment,BenedictineUniversity,Lisle,Illinois60532,USAmBrookhavenNationalLaboratory,Upton,NewYork11973,USAnAPC{UniversiteParis7DenisDiderot,10,rueAliceDomonetLeonieDuquet,F-75205ParisCedex13,FranceoClevelandClinic,C

3 leveland,Ohio44195,USApDepartmentofPhysi
leveland,Ohio44195,USApDepartmentofPhysics&Astrophysics,UniversityofDelhi,Delhi110007,IndiaqGEHealthcare,FlorenceSouthCarolina29501,USArDepartmentofPhysics,HarvardUniversity,Cambridge,Massachusetts02138,USAsHolyCrossCollege,NotreDame,Indiana46556,USAtDepartmentofPhysics,UniversityofHouston,Houston,Texas77204,USAuDepartmentofPhysics,IllinoisInstituteofTechnology,Chicago,Illinois60616,USAvDepartmentofPhysicsandAstronomy,IowaStateUniversity,Ames,Iowa50011USAwIndianaUniversity,Bloomington,Indiana47405,USAxHighEnergyExperimentalPhysicsDepartment,ITEP,B.Cheremushkinskaya,25,117218Moscow,RussiayPhy

4 sicsDepartment,JamesMadisonUniversity,Ha
sicsDepartment,JamesMadisonUniversity,Harrisonburg,Virginia22807,USAzNuclearNonproliferationDivision,ThreatReductionDirectorate,LosAlamosNationalLaboratory,LosAlamos,NewMexico87545,USAaaNuclearPhysicsDepartment,LebedevPhysicalInstitute,LeninskyProspect53,119991Moscow,RussiaabLawrenceLivermoreNationalLaboratory,Livermore,California94550,USAacLosAlamosNationalLaboratory,LosAlamos,NewMexico87545,USAadSchoolofPhysicsandAstronomy,UniversityofManchester,OxfordRoad,ManchesterM139PL,UnitedKingdomaeLincolnLaboratory,MassachusettsInstituteofTechnology,Lexington,Massachusetts02420,USAafUniversityofMinn

5 esota,Minneapolis,Minnesota55455,USAagMa
esota,Minneapolis,Minnesota55455,USAagMath,ScienceandTechnologyDepartment,UniversityofMinnesota{Crookston,Crookston,Minnesota56716,USAahDepartmentofPhysics,UniversityofMinnesotaDuluth,Duluth,Minnesota55812,USAaiCenterforCosmologyandAstroParticlePhysics,OhioStateUniversity,Columbus,Ohio43210USAajOtterbeinCollege,Westerville,Ohio43081,USAakSubdepartmentofParticlePhysics,UniversityofOxford,OxfordOX13RH,UnitedKingdomalDepartmentofPhysics,PennsylvaniaStateUniversity,StateCollege,Pennsylvania16802,USAamDepartmentofPhysicsandAstronomy,UniversityofPennsylvania,Philadelphia,Pennsylvania19104,USAanDep

6 artmentofPhysicsandAstronomy,Universityo
artmentofPhysicsandAstronomy,UniversityofPittsburgh,Pittsburgh,Pennsylvania15260,USAaoInstituteforHighEnergyPhysics,Protvino,MoscowRegionRU-140284,RussiaapDepartmentofPhysicsandAstronomy,UniversityofRochester,NewYork14627USAaqPhysicsDepartment,RoyalHolloway,UniversityofLondon,Egham,Surrey,TW200EX,UnitedKingdom2 arDepartmentofPhysicsandAstronomy,UniversityofSouthCarolina,Columbia,SouthCarolina29208,USAasSouthDakotaSchoolofMinesandTechnology,RapidCity,SouthDakota57701,USAatStanfordLinearAcceleratorCenter,Stanford,California94309,USAauDepartmentofPhysics,StanfordUniversity,Stanford,California94

7 305,USAavPhysicsDepartment,St.JohnFisher
305,USAavPhysicsDepartment,St.JohnFisherCollege,Rochester,NewYork14618USAawDepartmentofPhysicsandAstronomy,UniversityofSussex,Falmer,BrightonBN19QH,UnitedKingdomaxPhysicsDepartment,TexasA&MUniversity,CollegeStation,Texas77843,USAayDepartmentofPhysics,UniversityofTexasatAustin,1UniversityStationC1600,Austin,Texas78712,USAazTech-XCorporation,Boulder,Colorado80303,USAbaPhysicsDepartment,TuftsUniversity,Medford,Massachusetts02155,USAbbUniversidadeEstadualdeCampinas,IFGW-UNICAMP,CP6165,13083-970,Campinas,SP,BrazilbcInstitutodeFsica,UniversidadeFederaldeGoias,CP131,74001-970,Goi^ani

8 a,GO,BrazilbdInstitutodeFsica,
a,GO,BrazilbdInstitutodeFsica,UniversidadedeS~aoPaulo,CP66318,05315-970,S~aoPaulo,SP,BrazilbeDepartmentofPhysics,UniversityofWarsaw,Pasteura5,PL-02-093Warsaw,PolandbfPhysicsDepartment,WesternWashingtonUniversity,Bellingham,Washington98225,USAbgDepartmentofPhysics,CollegeofWilliam&Mary,Williamsburg,Virginia23187,USAbhPhysicsDepartment,UniversityofWisconsin,Madison,Wisconsin53706,USAbiDeceased. AbstractThispaperdescribesthehardwareandoperationsoftheNeutrinosattheMainInjector(NuMI)beamatFermilab.Itelaboratesonthedesignconsiderationsforthebeamasawholeandforindividualelements.Themostimp

9 ortantdesigndetailsofindividualcomponent
ortantdesigndetailsofindividualcomponentsaredescribed.Beammonitoringsystemsandprocedures,includingthetuningandalignmentofthebeamandNuMIlong-termperformance,arealsodiscussed.Keywords:Neutrinos,Longbaseline,Beam,Target,MainInjector. 1.IntroductiontoTheNuMIBeamTheNeutrinosattheMainInjector(NuMI)neutrinobeam[1,2]wasbuiltatFermilabtoprovideneutrinosfortheMINOS[3]experiment,along-baselineneutrinooscillationsearch,aswellasfortheCOSMOSexperiment[4],whichwasinitiallyapprovedbutsubsequentlywithdrawn.Later,theNuMIbeamwasusedforotherexperimentssuchasMINERA[5],ArgoNeuT[6],andmostrecentlytheNOA[

10 7]andtheMINOS+[8]experiments.Neutrinosfr
7]andtheMINOS+[8]experiments.NeutrinosfromNuMIhavealsobeenobservedandstudiedbytheMiniBooNEexperimentatalargeo -axisangle[9].3 TheNuMIbeamfacilityproducesneutrinosbysteeringa120GeVprotonbeamontoanarrowgraphitetargetapproximately1minlengththroughacolli-matingbae.Theproducedhadronsarethenfocusedintheforwarddirectionandcharge-sign-selectedbytwomagnetichorns.Mostofthehadronssubse-quentlydecayintoneutrinos(amongotherparticles)inalongdecaypipe.TheresultingneutrinobeampassesthroughdolomiterockandreachestheMINOSNearDetector(ND)1.04kmdownstreamoftheNuMItarget.Itthencontinuesfurthernorththroug

11 htheEarth'scrust,encounteringtheMINOSFar
htheEarth'scrust,encounteringtheMINOSFarDetector(FD)734kmawayintheSoudanMineinMinnesota,and nallyexitingtheearth12kmfurthernorth.ThispaperdescribestheNuMIbeamhardware,operationsandlong-termperformance.Itsfocusisthebeamcon gurationinplaceduringthedatatakingoftheMINOSexperiment,fromMay20,2005untilApril30,2012.DevelopmentsafterApril2012arebrie ydiscussedinSection5.TheNuMIbeam uxisdescribedseparatelyinacompanionNuMIbeam uxpaper[10].1.1.HistoricalBackgroundStartinggraduallyinthelate1980s[11,12,13]andwithever-increasingfrequencyinthemid-1990s[14,15,16,17,18,19,20,21,22],aplethoraofexperime

12 ntalindicationsemergedsuggestingthatneut
ntalindicationsemergedsuggestingthatneutrinoschangetheir avorastheypropagatethroughvacuumormatter.Thusabeaminitiallycreatedasapuremuon-neutrinobeammaydevelopanelectronortauneutrino avorcomponentasitpropagates.Ifthisphenomenonwereindeedtobeveri ed,itwouldprofoundlya ectourknowledgeofneutrinos.Accordinglyanumberofexperimentale ortswerethenbeingconsideredtoinvestigatetheseissuesunderwell-controlledexperimentalconditionswhichcouldbeobtainedwithanaccelerator-producedneutrinobeam.ItwasinthesametimeframethattheMainInjectoracceleratorwasbeingconstructedatFermilab.Thisacceleratorwoulduset

13 heFermilab8GeVBoosterasaninjectorandhave
heFermilab8GeVBoosterasaninjectorandhavetheabilitytoaccelerateprotonsupto150GeV1.TheNuMIdesignspeci cationscalledfor31013protonsacceleratedto120GeVevery1.87s[23].Theseparameterswouldallowcreationofneutrinobeamswithmuchhigherintensitiesthanhadbeenconstructedpreviouslyandthusmotivatedseveralgroupstoseriouslyconsiderneutrinooscillationinvestigations.Di erentgroupsproposedexperimentstoinvestigatedi erentregionsoftheparameterspacecharacterizingneutrinooscillations.Thee ortsthatshapedthedesignoftheNuMIbeaminvolvedstudiesofneutrinosoverdistancesoftheorderofseveralhundredkilomete

14 rs.Therewerethreeearlyproposalsforsuchex
rs.TherewerethreeearlyproposalsforsuchexperimentsbasedonabeamfromtheMainInjector;theonethathadmostin uenceonfuturedevelopmentsproposedtheuseoftheexistingSoudan2DetectorintheSoudanUndergroundLaboratoryinNorthernMinnesota[24, 1TheMainInjectorcanoperateatitsdesignenergyof150GeVbuttheoptimalneutrinorateisobtainedbyrunningitat120GeV,takingadvantageofafasterreprateatthislowerenergy.4 25].Thiswasfollowedbythemoreambitiousproposal[26]bythelargerMINOSCollaborationtoconstructbothanewbeamatFermilabandanewdetectorintheSoudanLaboratory.ThisproposalwasapprovedandshapedthedesignoftheNuMIbeam.1.2.DesignCons

15 iderationsAsaneutrinopropagates,the avor
iderationsAsaneutrinopropagates,the avorcompositionofitswavefunctionoscil-lates;thatis,therelativestrengthsofthecomponent avoramplitudeschangeastheparticletravelsthroughvacuumand/ormatter.Theprobabilitythataneutrinowitha avorstate atbirthwill,aftertravelingadistanceL,appearupondetectiontohave avor ,iswell-describedbythetwo- avorapproxima-tion:P ! =sin22sin21:27m2L E(1)wherethebaselineLismeasuredinkm,theneutrinoenergyEismeasuredinGeV,andm2isthemassdi erencesquaredbetweenthetworelevantmassstatesandismeasuredineV2/c4.The rstfactordetermin

16 estheamplitudeoftheoscillations,thesecon
estheamplitudeoftheoscillations,thesecondonetheirfrequency.Thee ectivemixingangleparametersin22andthemass-squareddi erencem2arefunctionsoffun-damentalparameterscharacterizingtheoscillations.Thenumericalfactor1.27takesaccountoftheunitsusedintheaboveequation.Fortheoscillationstobesigni cantm2Lshouldbe&Eusingtheunitsabove.ThustheoptimumdistancebetweenthesourceandthedetectordependsuponthevaluesofbothEandm2.AtthetimeoftheNuMIbeamdesigntherewereindicationsthatm2laysomewhereintherangeof10�3�10�1eV2=c4[15,16].A120GeVprotonacceleratorcanecientlyproducean

17 eutrinobeaminthe1-10GeVenergyrange.There
eutrinobeaminthe1-10GeVenergyrange.Thereforeadistanceofafewhundredkilometers,suchasthedistancebetweenFermilabandSoudan,wouldsucientlycoverallpossibilities.Furthermoreoncethedistancewaschosen,theonlyremainingfreeparameterinthedesignwastheenergyoftheneutrinos.Flexibilityintheenergyofthebeamwasdesirabletorespondtonewknowledgeofm2.Ahigh-intensitybeamwasrequiredtoachieveameaningfuleventrateattheMINOSdetectorseveralhundredkilometersawayastheneutrino uxfallswiththesquareofthedistancefromthedecaypoint.Thusoneoftheprimarydesignrequirementsforthebeamlinewastheabilitytowithstandahigh-powerprot

18 onbeam.Thedesignbeampowerwassomewhatopti
onbeam.Thedesignbeampowerwassomewhatoptimisticallysetto400kW,alittleabovethemaximumpowerthatcouldbeobtainedfromtheMainInjectorwhichwasalreadypushingthebeamtechnologyatthattime.A400kWbeampowerrequired41013protons/cycle,whereastheBoosterwascapableofdelivering31013protons/cyclewith6consecutiveinjectionsintotheMainInjector.Fora2scycletime,thisintensitycorrespondstoapproximately300kWbeampower.Theuseof\slip-stacking"techniques(discussedinmoredetailbelow)laterallowedthenumberofprotons/cycletobeincreased,butatthecostofincreasingthecycletimesincemoreBoosterbatchesneedtobeinserted.Thusthepower

19 doesnotincreaseasfastasprotons/cycle.5 F
doesnotincreaseasfastasprotons/cycle.5 Flexibilityoftheneutrinobeamenergywasachievedwithafocusingsys-tememployingparabolicmagnetichornswithadjustableseparationbetweenthemandthetarget,whichallowedtuningoftheenergyatwhichsecondaryparticleswerebestfocused[27].Forlowenergies,sincethedivergenceofthemesonbeamisgreateranddecaylengthshorter,widerdownstreamaperturesandlongeralloweddecaypathsaredesirable.Forhigherenergiestheapertureareaislessimportantbutlongerdecaypathsincreasethe ux.Arelativelylong(675m)andnotoverlywide(2mdiameter)decaypipegeometrywaschosen.Inhindsight,theactualm2turnedouttoberel

20 ativelylowandpreferredalow-energybeamfor
ativelylowandpreferredalow-energybeamforoscillationmeasurements.HenceabeamdesignedtodayexclusivelyforMINOSwouldhavealargerapertureandshorterdecay ightpaths.Theseconsiderations,togetherwiththeadoptedvaluesforthedimen-sionsofthetargetchaseandthedecaypipe,arediscussedmorefullyinSections2.2and2.7,respectively.2.NuMIBeamComponentsTheNuMIbeamispresentlytheworld'smostpowerfulneutrinobeamandisproducedbythe120GeVprotonsextractedfromtheFermilabMainInjector.AlayoutoftheacceleratorcomplexatFermilabisshowninFig.1.ProtonsoriginateasH�ionsintheLinacwhichacceleratesthemto400MeV.Theionsareconvertedintopro

21 tonsintheBoosterwheretheyareacceleratedt
tonsintheBoosterwheretheyareacceleratedto8GeVas1.6slongbatcheswitha53MHzbunchspacing.TheMainInjectorcir-cumferenceis7timesthecircumferenceoftheBooster.ThustheMainInjectorcanaccommodatestorageandaccelerationof6Boosterbatchesasoneofthese7slotsisneededforthepulsekickerrisetime.Inthelastfewyearsatechniquecalledslip-stackingwasdevelopedwhichallowedthecombinationoftwobatchesintooneafterinjectionintotheMainInjector.Useofthistechnique,togetherwithotherhardwareimprovementsandbetterdiagnostics,allowedasigni cantincreaseintheprotonintensitythatwasobtained[28].DuringmostoftheMINOSrun,oneoftheMa

22 inInjectorslotswasusedbyprotonsdestinedf
inInjectorslotswasusedbyprotonsdestinedfortheAntiprotonAccumulatorgeneratingantiprotonsfortheTevatronprogram,leaving veslotsforMINOSandgivingan8sspilltime.Aspillisde nedasonesetof veorsixprotonbeambatchesacceleratedtogetherasdescribedabove.WhentheAccumulatorwasnotoperationalallsixslotswereusedforNuMIgivinga10sspilltime.ThecycletimeforNuMIspillsrangedfrom2.1to2.4s.TheprotonintensityduringtheMINOSrunrangedfrom2.21013protonsontarget(POT)in2005toapproximately3.61013POTin2012.TheprotonsdestinedfortheNuMIbeamlineareextracted,bentdown-wardtopointattheMINOSFarDetector,a

23 ndtransported350mtotheNuMItarget.Theglob
ndtransported350mtotheNuMItarget.Theglobalpositioningsystem(GPS)wasoriginallyusedtode nethebeamdirection.Theprotonsareincidentonthegraphitetargetandthepro-ducedhadronsarefocusedbytwomagnetichornsandthenentera675mlongdecayvolume.Thehornsallowpreferentialselectionofhadronsofoneortheotherchargesign.Pionsandkaonsconstituteamajorportionofthehadrons6 Figure1:FermilabAcceleratorComplex.TheprotonacceleratorcyclefortheNuMIBeamstartswiththeLinacandisfollowedbytheBoosterandthentheMainInjector.TheTevatronwasoperationalduringmostoftheMINOSrunbutwasnotusedinneutrinoproduction.TheRecyclerisusedinthefol

24 low-up,post-MINOSexperiments(seeSections
low-up,post-MINOSexperiments(seeSections4.2and5formoreoperationaldetails).Alargenumberofbeamlinesshownwereconstructedforotherexperimentsandarenolongerinuseortheirfunctionhaschanged.TheAP1,AP2andAP3beamlines,AP0targetstationandtheringnamedMuonformedtheantiprotonsourcewhichisnolongeractiveandinthefuturesomeofthesewillbeusedformuonexperiments.TheP1andA1linesareprotonandantiprotoninjectionlinesfromtheMainInjectortotheTevatronandarealsonolongerinuse.TheP2andP3linesuseoriginalMainRingmagnetsandwerepartofthe xedtargetextractioncomplex.ThesquareslabeledMIsurroundingtheMainInjectorarevariousMainI

25 njectorservicebuildings. 7 Figure2:Schem
njectorservicebuildings. 7 Figure2:SchematicoftheNuMIBeam.TheindividualcomponentsoftheNuMIbeam(nottoscale)areshowntogetherwiththerelevantdimensions.Alltheimportantelementsareshown,includingthetarget,thehorns,thedecaypipe,thehadronabsorber,andtheso-calledmuonshieldwhichconsistsofthedolomiterockprecedingtheMINOSNearDetector.andpredominantlydecayviathemodes+!++andK+!++yieldingabeam.Thereisalsoafewpercentcomponentcomingfromnegativehadronsandasmallcontaminationofelectronneutrinos(e)duetosubdominantelectronicdecaymodeofK+hadrons,deca

26 ysofK0particles,anddecaysoftertiarymuons
ysofK0particles,anddecaysoftertiarymuons[10].Ahadronmonitorislocatedattheendofthedecayvolumejustinfrontofthe5mthickabsorbertorecordthepro leoftheresidualhadrons.Theseresidualhadronsareattenuatedtoanegligiblenumberbytheabsorber.Fouralcoveshavebeenexcavatedintherockjustdownstreamoftheabsorberandareusedtohousethreemuonmonitorsallowingmeasurementoftheresidualmuon uxwiththreedi erentthresholdenergies2.The240mofrockfollowingtheabsorberstopsthemuonsremaininginthebeambutallowstheneutri-nostopass.After240macavernhasbeenexcavatedtohousetheMINOSNearDetector.Thecavernsubsequentlyhousedadditional

27 experimentssuchasMINERAorArgoNeuT,t
experimentssuchasMINERAorArgoNeuT,takingadvantageofthehighneutrino uxatthatlocation.TheschematicoftheNuMIbeamisshowninFig.2.Theindividualbeamcomponentsaredescribedinmoredetailinthesectionsbelow.2.1.ThePrimaryBeamLineTheprimarybeamlineisatransferlinecarryingthe120GeVprotonsfromtheMainInjectortotheNuMItarget.ThereweretwocentraldesignprinciplesfortheNuMIprotonbeamline[29]:safeandlow-losstransmissionofaveryhigh-powerprotonbeamandaccuracyandstabilityoftargeting.Fractionallossesoverthe350mbeamlinewererequiredtobekeptbelow10�5.ThephysicsoftheMINOSexperimentrequiredthebeamtohaveanangularstab

28 ilityof60rad,andapositionalstab
ilityof60rad,andapositionalstabilityof250matthetarget.Typicaloperationalvaluesachievedwerefractionalbeamlosspriortothetargetpro lemonitorof310�7,angularstabilityof15rad,andpositionalstabilityof100m. 2ThefourthalcovewasnotinstrumentedduringMINOSrunning.8 TheprotonbeamisextractedfromtheMainInjectoracceleratorusing\single-turn"extraction.Asinglekickerbendsthebeamasmallangleintotheprimarybeamline,alsoknownasan\extractionchannel".Themagnetic eldinthekickerchangesfromzerotoitsfullvaluein700nswhichislessthanthelengthoftheextractiongapleftinthebeam.

29 Theentirebeamisdeliveredin10s,produ
Theentirebeamisdeliveredin10s,producingahighinstantaneousrateintheMINOSNearDetector.Analternativetechnique,resonantextraction,wouldallowamuchslowerspill(about1mslong)butwouldleadtounacceptableirradiationoftheMainInjectortunneldownstreamoftheextractionpoint.Inresonantex-tractionthetuneofthebeamisslightlychangedsothatthebeamexpandstowardsanelectrostaticseptumontheside,usuallyanarrayofanumberofwireswhose eldprovidestheinitialoutwardde ectionofthebeam.Themassoftheseptumiskeptaslowaspossibletominimizeprotoninteractionsbutitwasestimatedthattheminimumachievablelosswouldbe1-2%ofthebeamwhich

30 wasmuchtoohightobetolerable.Withsingle-t
wasmuchtoohightobetolerable.Withsingle-turnextraction,fractionalbeamlossismaintainedatpartpermillionlevels,asneededforthe400kWdesignNuMIbeam.Accordingly,itwasnecessarytoadoptsingle-turnextrac-tioneventhoughitnecessitatedmoresophisticatedelectronicsintheMINOSNearDetector.Single-turnextractionwasaccomplishedbyakickerconsistingofthreepulsedmagnetswithanintegrated eldof0.36Tm,followedbythreestandardMainInjectorLambertsonmagnetsandthenastandardCmagnet[23].TopointtowardstheSoudanLaboratorytheprotonbeamhadtobein-clineddownwardby58mrad.OneadvantageofusingtheMI-60locationforextractionwasthato

31 nlya59mradhorizontalbendwasnecessarytoai
nlya59mradhorizontalbendwasnecessarytoaimdi-rectlyatSoudan.Theoveralltrajectoryofthebeamlineforthe rst100mwasconstrainedtoahorizontalplanebyhavingto tbetweentheMainInjectormagnetsandRecyclermagnets.Therequiredtrajectoryinbothplanesinthispartofthebeamlinewasachievedbysixdipolesofvaryingrotationangles.Thesubsequentinitialverticaltrajectorywasdeterminedmainlybyissuesofcostandconstructability.Itwaspreferabletodomostoftheconstructioninsolidbedrockratherthansoiloverburden,andtominimizethepaththroughthewatertable.Thusthebeamwasinitiallyoverbentdownwardby156mrad(V108inFig.3),thenitwasbentbac

32 kupwardby98mrad(V118inFig.3)givinga
kupwardby98mrad(V118inFig.3)givinga nalverticalangleof58mrador3.343downwards3throughtheEarthtowardstheSoudanMineinMinnesota.Thebendingofthebeamwasachievedusingsix,andthenfour,refurbishedMainRingdipolemagnetsforthetwostages.Theregulationofthepowersuppliesforthedipolemagnetswas50ppmtoachievethebeamstabilityspeci cations.Theupper65mofthebeamlinethatpassesthroughthesoilandsoil/bedrockinterface,referredtoasthecarriertunnel,isuninstrumentedandcontainsa 3Theprecisenumberis3.34349,however,forthislevelofaccuracythelocationontheFermilabsitehastobespeci edasthecurvatureoftheearthb

33 ecomesimportant.Thenumber3.34349cor
ecomesimportant.Thenumber3.34349correspondstotheangleofthebeamintheTargetHallinlocalgravitycoordinates.9 Figure3:PlanandElevationViewsoftheNuMIBeamFacility.Theprotonbeamisdirectedontoatarget,wheresubsequentlythesecondarypionsandkaonsarefocusedintoanevacuateddecayvolume(later lledwithhelium)viamagnetichorns.Ionizationchambersattheendofthebeamlinemeasurethesecondaryhadronbeamandtertiarymuonbeam.vacuumtube.Theprotonbeamlineutilizes21standardFermilabquadrupoleswhosefunctionsaretomatchtheMainInjectoroptics,tooptimizethetrans-portedbeamforverylowbeamloss,andtocontrolthesize,divergenceandd

34 ispersionofthebeamatthetarget.Allprotonl
ispersionofthebeamatthetarget.Allprotonlinemagnetsarerampedforeachbeamcycletoreducetheoverallpowerconsumption.Theplanandeleva-tionviewsoftheNuMIbeamlineareshowninFig.3.TheverylowlossrequirementmandatesthattheNuMIprotonbeamenve-lopestaysclearofallaperturelimitations.Thus,thebeamlinewasdesignedwithlargeracceptancethanthatforthelargestbeamemittancethatcouldbeacceleratedintheMainInjector.Furthermore,anautomatedsystemmeasuredandcorrectedthebeamtrajectorypulse-to-pulse.Thebeamlinewasequippedwith19trimdipolemagnets,10horizontaland9vertical,toprovideprecisedirectioncorrectionsalongtheprotonpath.Anex

35 tensivesystemofbeampo-sitionmonitors,dis
tensivesystemofbeampo-sitionmonitors,discussedinSection3.1,providedthepositioninformationforthesecorrections.ThebeamspotattheNuMItargetisapproximatelycircularwithameasureddiameterof1.1-1.2mm(x=1:1mmandy=1:2mm).Fig.4showsthecalculatedprotonbeamenvelopecomparedwithmeasuredbeamwidths.Amoredetaileddiscussionoftheprotonbeamlineisprovidedin[29].2.2.TheNuMITargetHallTheNuMITargetHallconsistsofalargeundergroundcavernwhichcontainstheshieldingandallthesupportmodulesforthetarget,horns,andothermajorbeamcomponents.Thedesignpowerof400kWdictatesextensiveshieldingandthatthecomponentswithstandhighl

36 evelsofradioactivity,heating,andthermals
evelsofradioactivity,heating,andthermalshock.Inconsideringthedesignforanenclosureforthesesystems,severalthingsneededtobetakenintoaccount,includingthepromptradiationoccurringwhenthebeamstrikesthetarget,theresidualradioactivity,andtheactivationof10 Figure4:MeasuredandCalculatedBeamEnvelopes.TheenvelopesfromthekickermagnetsintheMainInjectortothetargetareshown.Thetargetislocatedat356minthisplot,about10mdownstreamofthelastmeasurementpoint.Themeasuredenvelopesaredisplayedasdatapoints,andthecalculatedonesareshownaslines.Theyareingoodagreementwitheachother.thesurroundingair,soil,andgroundwater.Inadd

37 ition,provisionhadtobemadeforremotehandl
ition,provisionhadtobemadeforremotehandlingofradioactivecomponentsforrepairandreplacement.TemporaryshieldedstorageisthereforeprovidedintheTargetHallforusedbeamcomponentsbeforetheyaremovedtomorepermanentstoragelocationselsewhereatFermilab.TheNuMITargetHallhasbeendesignedtoallowforthesaferunningandmaintenanceofallthebeamcomponents.TheTargetHallislocatedapproximately41mundergroundinthedolomiterockformationandisalongdomedchamber,approximately69mlong,8.1mwide,and12.5mhigh.Thisdepthwaschosensoastoprovideatleast6mofrockfoundationforthetargetandtheassociatedequipment,andenoughrockabovetheTargetHalls

38 otheroofwouldbeself-supporting.Fig.5show
otheroofwouldbeself-supporting.Fig.5showscross-sectionalviewsoftheHallincludingitsextensionattheupstreamend,andFig.6showsplanandelevationviewsoftheTargetHallcomplex.Thebeamlineextendsthroughapitabout6mwideand6mdeeprunningforover50muptothedecaypipe,whichprotrudes0.35mintothedownstreamendofthepit.Thepitfollowsthebeamdirectionatadownwardangleof3.343tothehorizontal.Thepitservesasthehousingforthebae/targetandthefocusinghornstogetherwiththeirsupportstructuresandauxiliaryequipment.Itislinedatthesidesandthebottomwithalayerofconcreteshieldingtoprovideatunnel4.7mdeepand4.3mwide.Thepitcross-s

39 ectionisshowninFig.5.Oneoftheelementssho
ectionisshowninFig.5.Oneoftheelementsshownissteelshielding,whichisinstalledinthistunneltoformacentral\chase"witharectangularcross-section,1.2mwideand1.3mhigh(essentiallyabeampassageway).Beamlinecomponentsandinstrumentationareinstalledinthischase;thechasealsoservesasachannelfortherecirculationofchilledairfromanaircoolingsystem.Multiplecon gurationsofbeamcom-11 ponentswereenvisioned,thehighestenergycon gurationhavingaseparationbetweenhornsofupto40m.Thusa60mtotallengthoftheTargetHallwasdeveloped.Thesteelshieldingiscomposedofatotalof633Duratek10tonsteelblocks4,witheachblockhavingthedimen

40 sions1.33m1.33m0.67m.Thesteelblo
sions1.33m1.33m0.67m.Thesteelblocksarestackedinaninterlockingmannerandlayersarestaggeredwithrespecttoeachothertoavoidalignedgaps.46cmthickconcretecovers,in0.9mlongitudinalsegments,areusedtoprovideshieldingontop.TheTargetHallalsocontainsastriplineforpoweringthehorns.ThecalculatedheatloadfromthebeaminthenormalNuMIbeamlowenergycon gurationintothetargetpileis158kW.Theremovalofthisheatandadditionalheatfromhorncurrentandelectricaldevicesisimportantforthecorrectfunctioningofthebeam.Thisfunctionisprovidedbyarecirculatingaircoolingsystemdesignedfor240kWofcooling.Inadditionthesystemprovide

41 sdehumidi cationanda ltertoremov
sdehumidi cationanda ltertoremoveparticulatesdownto0.3minsize.Sincemaintainingalignmentofthetargetandhornswiththeprimaryprotonbeamiscritical,theentirechainofmountingthosecomponentstothebedrockmustcontrolthermalexpansione ects.Theair-coolingequipment,dehumidi ersand ltersareinstalledalongsidethedownstreamendofthechase.Airatrocktemperatureissuppliedatthatendtothespacebetweentheconcreteshieldandthesteelinnershielding;thisair owsthroughtheretotheupstreamendofthetargetpile.Thismaintainsthethermalstabilityoftheconcrete.Thehornsandtargetsaremountedatbeamheightonwater-cooled

42 hangers,whichhangonlowthermalexpansionro
hangers,whichhangonlowthermalexpansionrods.Therodspenetratethroughthesupportmodulesandareattachedatthetopofthemodules.ThoseearsatthetopofthemodulesrestonI-beamstructuresthataresupportedbytheconcrete.Alltheshieldingsteel,bycontrast,issupportedbythebottomofthetargetpile,andexpands/contractsindependentlyofthetargetandhornsupports.ControlledwidthcracksaresetatthetopoftheT-block5shieldingandmodulessothatsomeofthecirculatingairiscoolingthestripline,rods,T-blocksetc.Theairisdirectedfromthetopofthemodulesintocentralshieldingtominimizeradioactivecontaminationinplacesusedbypersonnelwhentheyneedtoworko

43 nthemodules.Theairturnsaroundattheupstre
nthemodules.Theairturnsaroundattheupstreamendofthetargetpile,andthencomesdownstreamthroughthecenterofthechase,passingbythetargetandthehornsandremovingtheheatfromthesteelshielding.Atthedownstreamendtheairis ltered,chilledanddehumidi ed,andthenpushedbyafanbackforanotherpass.TheTargetHallwallssupportacraneof30tonloadcapacityhangingfromguidingtrackswhichallowstheliftingandmovingofNuMIbeamcomponentsandshielding.Thecranecantravelinthedirectionofthebeambetween2.4mand64.3mfromtheupstreamfaceoftheTargetHall.Thetravelofthecrane 4DuratekBluBlockscastbyDuratekInc.atOakRidgeNationalLaboratoryfrom

44 scrapironandsteel.5AT-blockisaspeciallys
scrapironandsteel.5AT-blockisaspeciallyshapedshieldingblockthathasasteelbaracrossthetopcreatingaT-shape;thisbarisusedtoresttheT-Blockontheshieldingwalls.12 trolleyinthetransversedirectionisabout5.5m.Asystemoftenvideocamerasallowsthesafeoperationofthecranefromaremotelocationandallowstheprecisionplacementandliftingofcraneloads.ThevideosignalsaretransmittedbywirelessandwiredconnectionstoreceiversattheupstreamendoftheTargetHall.Theremotecraneoperationisessentialforrepairandreplacementoftargetandhornassemblies.UsedbeamelementsaremovedasaunitwiththeirsupportmodulestotheWorkCellusingtheoverheadcran

45 e.TheWorkCellisawell-shieldedfacility,lo
e.TheWorkCellisawell-shieldedfacility,locatedatthedownstreamendoftheTargetHall,thatallowsinstallation,inspection,and,ifnecessary,replacementofbeamcomponents.Insomecasesithasbeenpossibletorepairfailedtargetsandhorns.TheWorkCellisshieldedby0.9mofconcreteonitseastandwestsidesand0.3mofsteelonthenorthandsouth.Thesteelwallonthesouthsideisremotelymovablebyslidingittotheeast.Therearefourapertures,threeintheeastwallandoneinthenorth,whichare lledwithlead-glassblocksallowingtheviewingofthebeamelementsinthecellduringremoteoperations.Removedelementsaretemporarilystoredinawell-shieldedlocationdubbedth

46 e\morgue",withinthetargetshieldpile.Thee
e\morgue",withinthetargetshieldpile.Theelementscanlaterberecoveredafteracertaincool-downperiod,andsenttolong-termstorage.TransportationoutoftheTargetHallorotherstoragefacilitiesrequiresspeciallymadeshieldcaskstoreduceanyincidentalradiationexposure.TheprimarypersonnelaccesstotheTargetHallisthroughtheelevatorattheupstreamendoftheHall.Astairwayprovidesalternativeaccess.ThemajorpiecesofequipmentareloweredintotheHallwithacranethrougha36.6mdeepshaft.Theshaftiscloseto,butnotsituateddirectlyoverthemainTargetHallchamber.Thecarriertunnelontheupstreamendanda670mlongpassagewayalongthedecaypipeprovideadd

47 itionalemergencyexitpaths.TheTargetHalli
itionalemergencyexitpaths.TheTargetHallisaveryhighradiationarea,especiallywhenthebeamisoperating,andassuchitisunderapersonnelsafetyinterlocksystemthatisfailsafeandredundant.ThissystempreventspersonnelaccessduringbeamoperationtothePre-targetandTargetHallenclosures.Thepowersupplies,thecontrolsystemsandassociatedequipmentarelocatedinanadjoiningenclosureoutsideoftheinterlockedsystem;theyareaccessibleduringbeamoperation.2.3.TheBaeThedesignpoweroftheNuMIbeamissohigh(upto400kW)thatevenarelativelysmallmis-steeringofthebeamcouldcausesigni cantdamagetothebeamcomponents.Asinglepulseofmis-steer

48 edbeamcoulddestroyaprimarybeammagnetoraT
edbeamcoulddestroyaprimarybeammagnetoraTargetHallcomponentsuchasafocusinghorn.Especiallyvulnerablearethetargetcoolingandsupportcomponentsandthemagnetichornswhosenarrowestapertures(referredtoasnecks)arenotmuchlargerthanthenominalbeamsizeattheirlocations.Theconstructionofhorns,fromafewmillimeterthinaluminium,makesthemfragileenoughthattheyhavetobeprotectedfromanylargesuddenenergydeposition.Toprovidesuchprotectionaspeciallydesigneddevice,referredtoasthebae,hasbeenconstructedandinstalledjustupstreamofthetarget.13 Figure5:TheNuMITargetHallCrossSection.TheleftpartoftheFigureshowstheTargetHallc

49 rosssectionincludingtheaccessshaft,stair
rosssectionincludingtheaccessshaft,stairwayandtheauxiliaryroomsandthemorgueusedtotemporarilystoreremovedbeamcomponents.TherightpartdetailstheTargetHallitselfincludingshielding,thetargetchasewiththetarget,andalsothecraneusedformovingbeamcomponents.Thebaeconsistsofagraphitecore,1.5mlongalongthebeamdirectionand57mmindiameter,encasedina60mmO.D.aluminiumtube.Atthecenterisan11mmdiameterholethroughwhichtheprotonbeampasses.Thebaeisdesignedtodegrademis-steeredbeamenoughthatthetargetandhornsarenotdamaged.Itisdesignedtowithstand,withoutdamage,thefullintensitybeamforashorttime(afewpulses)until

50 mis-steeringcanbedetectedandthebeamshuto
mis-steeringcanbedetectedandthebeamshuto .Thermocouplesinstalledonthebaeareconnectedtoaninterlockwhichwillturnthebeamo ifsigni cantmis-steeringisdetectedasexcessiveheat.Thismonitoringalsoprovidesameasureofhowmuchbeamis\scraping",orhitting,theinsidewallsofthebae.Bothmonitoringfunctionsareprovidedbymeasuringthetemperatureatthedownstreamendofthebae.Thebaeisdesignedtobeabletooperatecontinuouslywithupto3%ofbeamscrapingatdesignluminosity,andmeasurescrapingwithanaccuracyofatleast1%oftheprotonbeam.Thebaeholeisapproximately5intermsofthetypicalbeamspotsize

51 ,soforproperlysteeredbeamonlynon-Gaussia
,soforproperlysteeredbeamonlynon-Gaussiantailsofthebeamareasourceofbaescraping.Duringnormaloperation,theheatingofthebaehascorrespondedtoanestimated0.6%ofbeamscraping,butthisisanoverestimateasheatingfrombackscatterradiationfromthetargethasnotbeensubtracted.Thebaeismountedonthesamecarrierasthetargetsothattheyaremovedtogetherwhenthebeamcon gurationischanged.Thebaehasberylliumwindowsthatwouldcontaintheradioactivatedgraphiteif14 Figure6:ThePlanandElevationViewsoftheNuMITargetHall.ThelocationsoftheprincipalbeamelementsareshownaswellasalternateHorn2locationsforpotentialhighe

52 renergycon gurations.Alsoshownarethe
renergycon gurations.AlsoshownarethelocationsofthemorgueandtheWorkCell.itpowdered.Italsohasaventilationholewhichpreventsairpressurebuild-up.AschematicofthebaeisshowninFig.7.2.4.TheNuMITargetThetarget[27]isoneofthemoredelicateelementsintheNuMIbeamline.Thetargetmustbeabletowithstandthe400kWdesignpowerwithoutdisintegrating,whilemaximizingtheproduced uxofhadronsandhencetheneutrinoyield.Tomaximizetheneutrino ux,mostoftheprotonbeamshouldbeinterceptedinthetargetinthesmallestpossiblevolumesoastominimizethenumberofsubsequentsecondarymesoninteractions.Thisthereforerequiressmalltransversetarge

53 tdimensions.Ontheotherhand,thetargetisma
tdimensions.Ontheotherhand,thetargetismademorerobustbyenlargingboththebeamsizeatthetargetandthetargetitself,reducingvolumetricenergydepositionandgradientsandmaintainingahighfractionofthebeamstrikingthetarget.ThetargetismadeofgraphiteofthetypeZXF-5Q(POCOgraphite)withadensityof1.78g/cm3.Itconsistsof47 ns,eachofwhichis20mmlong(alongthebeamdirection),15mmtall,and6.4mmwide;the nsarespaced0.3mmapartgivingatotaltargetlengthof95.38cm.The nsarebrazedinvacuumtotwostainlesssteelpipeswhichconductthewatercoolant;thepipes'externaldiameteris6mmandwallthickness0.2mm.Inadditiontothose ns,a48t

54 hsegmentismountedhorizontallyinthetarget
hsegmentismountedhorizontallyinthetargetcanister15.73cmupstream15 Figure7:TheNuMIBeamBae.Isometricandcross-sectionalviewsareshownofthebaewhichis150cmlong,andhasa57mmdiametergraphitecorewithan11mmdiameterborethroughthemiddle.Itisencasedby60mmdiameteraluminiumtube.ofthemaintarget.Theverticalalignmentformostofthetargetswassetbycenteringthebeaminthebaeandrelyingonthesurveyedslope6.Thisextra nisusedinthebeam-basedalignmentprocedureasdiscussedinSection4.1.Forlowenergyrunningthetargetwasinserted50.4cmintothe rsthorntoobtainthemaximum uxpossibleinthe1-3GeVrange.Inthiscon g

55 urationtheclearancebetweenthelasttarget&
urationtheclearancebetweenthelasttarget nandthehornconductorisjustafewmm.ThetargetstructurewasanalyzedusingMARS[30]forenergydepositionand nite-elementmechanicalmodeling.Mechanicalstresses,temperatures,andcoolingcapabilitywereevaluatedforthehighestprotonintensitiesenvisaged.Thecalculatedmaximuminstantaneoustemperaturerisewas288Cgivingamaximumtemperatureafterabeamspillof344C.Stressesinthetargethavebeencalculatednottoexceed25.6MPa,comparedto36MPa,theestimated 6Forthe rstNuMItarget(NT-01)the48thsegmentwasmounted2.26mmaboveitsverticalcenterasthetargettubewasbentattheconnecti

56 onbetweenthetubeandthebaseshortlybeforei
onbetweenthetubeandthebaseshortlybeforeinstallation.Thismeantthatthecross n,whichismountedtothemaincanratherthanthetube,wasmisalignedand2.26mmhigh.Forsubsequenttargets,aprotection xturefortargettipswasbuiltthatwouldgetremovedjustbeforeinstallationintheTargetHall;thisresultedinnootherbenttargettubes.Consequently,themisalignmentforthesecondtarget(NT-02)wasonly0.3mmaccordingtosurvey,andforthethirdtarget(NT-03)itwas0.9mm.16 fatiguelimitofthegraphiteused.Theheatloadisestimatedas3.04kWgivingawatertemperatureriseof12Cassumingawater owrateof3m/s.Berylliumwindowsareusedattheentranceandex

57 itofthetargetvesseltoprotectthegraphites
itofthetargetvesseltoprotectthegraphitestructure.Thetargetcanisterandcasingcompriseavesselwhichprovidestheprimarycontainmentforthetarget.Thetargetcanisterismadeofasolidpieceofaluminiumalloy,andsurroundsthevolumeupstreamofthetarget.Thetargetcasingisathinaluminiumtubesurroundingthetargetsegments.Thetargetcanbeevacuated,butisnormallyoperatedinheliumgassomewhataboveatmosphericpressure.Anodizedaluminiumspacersprovideelectricalisolationofthetarget nsandthecoolingtubesfromthetargetcasingandthe rsthorntopreventanydischargebetweenthetargetandthehorninnerconductor.Thetargetandtargetcanisterdes

58 ignareshowninFig.8.AhorizontalBudalmonit
ignareshowninFig.8.AhorizontalBudalmonitor[31]consistingofawireconnectedtothecoolingtubeallowsthemeasurementofdelta-raychargeknockedoutofthetargetwhenitishitbythebeam.ThehorizontalBudalmonitorallowsthebeamtobescannedhorizontallyacrossthetargettocheckthetargetpositioninthisdimension.AnotherBudalsignalreadoutislocatedontheadditional48th nandprovidesapositioncheckforbeamscansintheverticaldirection.Thecoolingforthissegmentisprovidedbyconductionthroughitsclampingplatestothecanister.Theclampingplatesareanodizedtoprovidetherequiredelectricalisolation.Fig.9showsabeam-eyeviewofthebaeinnerape

59 rturesuperimposedonthebeamspot,thetarget
rturesuperimposedonthebeamspot,thetarget n,thehornneckandthetargetcoolingandsupportstructure.2.5.TheTarget/BaeCarrierStudiesofbeamcomposition[10]requiretheabilitytomeasureneutrinoenergyspectraindi erentbeamcon gurationswithdi erentenergies.Thusitwasfoundveryusefultobuildinasystemthatwouldallowenergychangeswithverylittledown-time,whichinturnimpliesthatthechangeswouldhavetobedoneremotelywithoutaccesstotheradiationareas[32].Themovablecarriersystemthatwasadoptedaccomplishesthiswithabouta25%penaltyin uxcomparedtothemoreextensivebeammodi cationsrequiredforoptimizedhigheren

60 ergycon gurationsdiscussedintheSecti
ergycon gurationsdiscussedintheSection2.6[33,32].Inthismethodthetwohornsremainintheirstandardlowenergypositionsbutthetargetismovedwithrespecttothe rsthorn.Thetarget/baecarriersystemisshowninFig.10.Thebaeandthetargetaremounted68cmfromeachotheroncradlesthathaverollersthatrideonaluminiumrailscoatedwithtungsten-disul defortoughness.Thisallowsthebaeandthetargettobemovedasoneunitwithrespecttothehornswhenthebeamcon gurationneedstobechanged.Furthermore,thecarriersupportstargetandbaeutilitiessuchasthetargetcoolingwatersupply,thetargetwaterreturnline,thetargetvacuum

61 line,theeightthermocoupleelectricallines
line,theeightthermocoupleelectricallinesandthetwoBudaltargetmonitorelectricallines.Thosedi erentlinesareloopedbelowthecarrierandareattachedtothecarrierattheupstreamend;thedownstreamendsofthelinesmovewiththecradles.Thecarrierhangs17 Figure8:LongitudinalCross-SectionoftheNuMITargetandtheTargetCanister.18 Figure9:Beam'sEyeViewoftheBaeInnerAperture.This gureshowswhattheprotonbeamseesasittravelsthroughtheNuMIbaeandhitsthetarget.Superimposedonthediagramarethebeamspot,thetarget n,thehornneck,andthetargetcoolingandsupportstructure.Alldimensionsareinmm.19 fromtwoshaftsthatpenetr

62 atethroughaheavyshieldingmodule.Position
atethroughaheavyshieldingmodule.Positioningmotorsmountedontopofthemoduleallowmotioncontrolofthetarget8mmhorizontally,and+8/�200mmvertically.Formaintenance,themoduleandcarrieraremovedtotheWorkCell.Whenanewtargetisrequireditis rstinstalledonthecarrierinthemediumenergypositionsothatthetargettipandbaearenotstickingoutoftheendsofthecarrierduringthestepofmoduleinsertionintothetargetpile.Thelongitudinalpositioningandreadbackoflocationofthetargetisalldoneopticallyafterinsertion.Subsequentlyabeamscanisperformedbyslowlysteeringthebeamthroughasequenceofcloselyspacedhorizontallocationsan

63 dthecarrierisalignedtransverselywiththeb
dthecarrierisalignedtransverselywiththebeamlineusingthemodulemotordrives.Thetargetandbaesystemisthenmovedonthecarriertothedesiredlongitudinalposition.Anotherbeamscanisthenperformedtoseeifadditionaltransverseadjustmentisneeded.Thesameprocedureisalsofollowedwhenitisdesiredtochangetheenergybymovingthetargetwithrespecttothehorns.Thetypicalbeamdown-timeforthiswholeoperationisaboutoneday.Thetargetcanbepositionedwithanaccuracyof0.5mmtransversely.Lon-gitudinally,itcanbepositionedtoanaccuracyof1cm,andthenthepositioncanbesurveyedwith0.3cmaccuracy.Thebae/targetcarriersystemwasdesignedtomainta

64 inpositiontowithin0.5mmtransverselyand1m
inpositiontowithin0.5mmtransverselyand1mmlongitu-dinallyunderbeamheatingconditionscreatedbyupto41013POTstrikingthetargetevery1.87s.TheNuMIcarriersystemsusedoverthecourseoftheMI-NOSexperimentweredesignedtosurviveradiationdosesofupto1011rad/yearforupto10years.2.6.TheMagneticHornsThesecondarymesonsproducedfromthetargetarefocusedbytwomagnetichorns[34],Horn1andHorn2,whichessentiallyactashadronlenses.ThehornsareillustratedinFig.11.Thehornssigni cantlyincreasehadron uxinthedesiredenergyrangeandprovide exibilityinchoosingthatenergy.Thetargettohorndistanceis exibleandtheseparationbetweenthetw

65 ohornscanalsobechanged.Thedesignaccommod
ohornscanalsobechanged.ThedesignaccommodatesthreepotentialHorn2positionsof10m,23m,and37mdownstreamfromthezeroposition(takentobetheupstreamendofHorn1),correspondingtolow,mediumandhighenergyrespectively,coupledwithappropriatetargetmovementupstream.IntheMINOSexperimenttheoptiontomoveHorn2wasneverexercisedgiventheprevailingwisdomonm2bythetimeNuMIturnedon7andtheMINOSmediumandhighenergycon gurationswereachievedbymovingthetargetwithrespecttoHorn1andadjustingthehorncurrent.TheresultingMINOS\pseudo"mediumandhighenergyrunswereshortspecialrunsusedforbeamstudies.Fig.12showsa 7Horn2remainedinthel

66 ow-energypositionduringtheMINOSexperimen
ow-energypositionduringtheMINOSexperiment.Thesub-stantialshieldingmodi cationsneededtomovethehornwouldhaveresultedinanunac-ceptablylongdownperiod.Furthermore,physicsconsiderationsgenerallypreferredrunningwithHorn2inthelow-energypositionsoastomaximizetheamountofdataattheneutrinooscillationpeak.20 Figure10:TheTarget/BaeCarrierSystem.ThetopFigureshowsaschematicofhowtheNuMItargetandthebae ttogetherinthecarriersystem.Thebottom gureshowsanisometricofthecarriersystemitselfwhichhasboththetargetandthebaemounted.Thetarget/baecombinationcanbeextendedoutintothefocusinghor

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