NewLowTNitrogenTreatmentsCavityResultswithRecordGradientsandQ A Grassellino S AderholdTTC SaclayJuly7th 2016 Motivationbehindexperiments CompositionandmeanfreepathinfirstnanometersofcavitysurfacehavebeenshowntobecrucialforbothQandgradientperformanceNDopingatT 800Cproventomanipulatemeanfreepath butconstantlythroughoutseveralmicrons givinghighQ120Cbakeknowntomanipulatemeanfreepathatverynearsurfaceoncleanbulk andproducethehighestgradients 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 2 120Cbake vacanciesinfirst 60nanometers Ndoping nitrogenthroughoutseveralmicrons A Romanenkoetal Appl Phys Lett 102 232601 2013 A Grassellinoetal ProceedingsofSRF2015 Motivationbehindexperiments Therefore wedecidedtostudyhowtobetter engineer adirtylayerontopacleanbulk usinglowTnitrogentreatments aimtocreatefewtoseveralnanometersofnitrogenenrichedlayerontopofcleanEPbulk toattempttobringtogetherthebenefitoftheQandgradientNitrogenenrichednanometriclayertobecreatedinthefurnacepost800Ctreatment whennooxideispresentatthemomentofinjectionofnitrogenatlowTStudiesaimalsoatfundamentalunderstandingofHFQSand120CcureofhighfieldQslope 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 3 AllresultsinthispresentationsoontoappearonarXiv A Grassellinoetal AllQvsEcurvesshownarefor1 3GHzsinglecells T 2K Thesurfaceof120CbakevsNdopingvsEP viaLE muSR 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 4 Ba 25mT mfp 2nmatthesurface attemptsubstitutewithN2 15nm noscreening mfp 70nm mfp 400nm Meissnerscreeningprofilesfordifferentlytreatedcutouts Bamagneticfieldappliedparalleltosamplesurface 25mT Allowstodirectlyextractsurfacemfp Producesamedirtylayerprofileas120Cbake butwithnitrogen ratherthanvacancies ObtainbenefitofBCSANDgradient M Martinelloetal submittedtoAPL Exampleofnewsurfaceprocessingsequence Grassellino Aderhold Highgrad highQviaNinfusion 5 Bulkelectro polishingHighTfurnacewithcapstoavoidfurnacecontamination 800C3hoursHV120C48hourswithN2 25mTorr NOchemistrypostfurnaceHPR VTassembly 7 7 16 A Grassellinoetal arXiv 1305 2182 ProtectivecapsandfoilsareBCP dpriortoeveryfurnacecycleandassembledincleanroom priortotransportingcavitytofurnacearea Resultscomparison standard 120Cbakevs Ninfused 120Cbake Grassellino Aderhold Highgrad highQviaNinfusion 6 Samecavity sequentiallyprocessed noEPinbetweenAchieved 45 6MV m 194mTWithQ 2e10 Qat 35MV m 2 3e10 IncreaseinQfactoroftwo increaseingradient 15 7 7 16 Reproducibility repeatedlyhighestQevermeasured 2e10atveryhighgradients 40MV m Grassellino Aderhold Highgrad highQviaNinfusion 7 Sofarthreeoutof4cavitiesprocessedwiththisregimehavereached45MV mwithhighQPerformedslowcooldownin10mGandextractedverylowsensitivitytoBonorderof0 3nOhm mG veryrobustforQpreservation 7 7 16 Sequenceonsamecavity EP 800C 120Cbake 800C N infused120Cbake Grassellino Aderhold Highgrad highQviaNinfusion 8 ClearevolutiontrendconfirmingimprovementinQandquenchfieldNOEPbetweenfurnacetreatments comparingsamemorphologicalsurface justdifferentimpuritycontent 7 7 16 Isnitrogenreallyplayingaroleat120C Repeatedsameprocedurewithandwithoutnitrogeninfurnaceat120CHoldingat120Cinfurnacefor48hourspost800CwithoutthenitrogendoesnotcompletelyremovethehighfieldQ slopeItpushestheonsetofHFQStohigherfields 30MV mNitrogenisneededtoremoveHFQScompletelyandachievehighestfields 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 9 Buthowdeepisnitrogentoproducesuchaneffect FirstSIMSmeasurementsonsamplesbakedwithcavitiesinfurnacewithNatlowTshow 5nmpotentialnitrogenenrichedlayer 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 10 Explorationatothertemperatures DecidedtoexploreothertemperaturesforNinjectionlike160C 200CorsameT120Cbutlongertime toverifyifdiffusionofNdeepercorrelateswithchangeinperformanceResultsinslidesthatfollowshowhowincredibleanddramaticthemodificationofBCSandresidualresistancecanbewithjustnanometerchangesinsurfaceimpuritycontentItdoesshowhowfortunateweweretostumbleacrossthestandard120Cbakewhich miraculously workswell 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 11 Cavityevolution 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 12 Cavityevolution 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 13 Cavityevolution 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 14 Cavityevolution 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 15 IncreasingT 40Cturnscavityinto dopedshape Cavityevolution 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 16 IncreasingT 40Cturnscavityinto dopedshape Increasingdurationx2turnscavityinto dopedshape evenhigherQ Commentstoresultssofarandpathforward Wehavefoundapowerfulstrategytomanipulatesurfaceimpuritycontent andgethigherQ 2e10atEacc 35MV mVeryHighQ 4e10achievablewithlowTnitrogentreatmentNolowerquenchlimitsobserved butneedtofix slopes togettheQ 3e10uptohighestfieldsTounderstandoriginofQimprovementandQ slopesobserved weanalyzedthesurfaceresistanceviadecompositionintoRBCSandR0asfunctionoffield 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 17 Decomposition systematicchangesinRBCS H 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 18 120C48hrswithN2infurnacevsstandard120CpostoxidationreducesslightlytheRBCS H butsameshape120C96hrsor160C48hrswithN2infurnacedrivetheRBCS H tothatofadopedcavity inversefielddependence BUT newfinding QslopelimitingQ 3e10athighgradientemergingfromBCS PreviouslyunseenPerhapsindicatesthatN infusedlayeristoothin 200Cchangesshape notunderstood Decomposition systematicchangesinR0 H 7 7 16 Grassellino Aderhold Highgrad highQviaNinfusion 19 120C48hrswithN2infurnacevsstandard120Cpostoxidationreducesclearlytheresidualresistance especiallyathigherfieldsSeemsthatimprovementinQatEacc 30MV mstemsinlargerportionfromresidualasafunctionoffieldSonitrogenat120CmainlyplaysroleofeliminatingHFQS andperhapsimprovementinresidualcomesfromlackofsuboxidespost120Cbake HFQSvisibleintheresidualofthecavitybakedat120Cpre oxidationandwithnonitrogen Conclusions 1 2 RecipethatsystematicallyimprovesQ 1 3GHz 2K 2e10atEacc 30MV 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