Superconducting Radiofrequency Technology for Accelerators: State of the Art and Emerging Trends

398 Pages·2023·17.924 MB·English

by  Hasan Padamsee

SuperconductingRadiofrequencyTechnologyforAccelerators

Superconducting Radiofrequency Technology
for Accelerators
State of the Art and Emerging Trends
Hasan Padamsee
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v
Contents
Preface xi
PartI UpdateofSRFFundamentals 1
1 Introduction 3
2 SRFFundamentalsReview 7
2.1 SRFBasics 7
2.2 FabricationandProcessingonNb-BasedSRFStructures 11
2.2.1 CavityFabrication 12
2.2.2 Preparation 12
2.2.3 ADecadeofProgress 15
2.3 SRFPhysics 15
2.3.1 ZeroDCResistance 15
2.3.2 MeissnerEffect 17
2.3.3 SurfaceResistanceandSurfaceImpedanceinRFFields 19
2.3.4 NonlocalResponseofSupercurrent 22
2.3.5 BCS 24
2.3.6 ResidualResistance 30
2.3.7 SmearingofDensityofStates 31
2.3.8 Ginzburg–Landau(GL)Theory 31
2.3.9 CriticalFields 34
2.3.10 ComparisonBetweenGinzburg–LandauandBCS 39
2.3.11 DerivationofR andX 39
s s
PartII HighQFrontier:PerformanceAdvancesand
Understanding 43
3 Nitrogen-Doping 45
3.1 Introduction 45
3.2 N-DopingDiscovery 46
3.3 SurfaceNitride 48
vi Contents
3.4 InterstitialN 49
3.5 ElectronMeanFreePathDependence 52
3.5.1 LE-μSRMeasurementsofMeanFreepath 53
3.6 Anti-Q-SlopeOriginsfromBCSResistance 55
3.7 N-DopingandResidualResistance 58
3.7.1 TrappedDCFluxLosses 58
3.7.2 ResidualResistancefromHydrideLosses 58
3.7.3 TunnelingMeasurements 59
3.8 RFFieldDependenceoftheEnergyGap 61
3.9 FrequencydependenceofAnti-Q-Slope 63
3.10 TheoriesforAnti-Q-Slope 63
3.10.1 XiaoTheory 63
3.10.2 GurevichTheory 68
3.10.3 NonequilibriumSuperconductivity 72
3.10.4 Two-FluidModel-BasedonWeakDefects 75
3.11 QuenchFieldofN-DopedCavities 77
3.12 EvolutionandComparisonofN-dopingRecipes 83
3.13 HighQandGradientR&DProgramforLCLS-HE 83
3.14 N-DopingatOtherLabs 88
3.15 SummaryofN-doping 88
∘
4 HighQvia300 CBake(Mid-T-Bake) 91
4.1 ASurpriseDiscovery 91
4.2 SimilaritiestoN-Doping 91
4.3 Mid-TBakingatOtherLabs 95
∘
4.4 TheLow-FieldQ-Slope(LFQS)and340 CBakingCures 97
4.5 LossesatVeryLowFields 100
4.6 LossesfromTwo-LevelSystems(TLS) 100
4.7 EliminatingTLSLosses 101
5 HighQ’sfromDCMagneticFluxExpulsion 105
5.1 TrappedFluxLosses,Sensitivity 105
5.2 TrappedFluxSensitivityModels 106
5.3 VortexPhysics 108
5.4 CalculationofSensitivitytoTrappedFlux 110
5.5 DependenceofSensitivityonRFFieldAmplitude 112
5.6 DCMagneticFluxExpulsion 114
5.6.1 FastversusSlow-CoolingDiscovery 114
5.6.2 ThermoelectricCurrents 118
5.7 CoolingRatesforFluxExpulsion 122
5.8 FluxExpulsionPatterns 123
5.9 GeometricEffects–FluxHole 127
5.10 FluxTrappingWithQuench 127
5.11 MaterialQualityVariations 129
5.12 ModelingFluxTrappingFromPinningVariations 135
Contents vii
PartIII HighGradientFrontier:PerformanceAdvancesand
Understanding 139
6 High-FieldQSlope(HFQS)–UnderstandingandCures 141
6.1 HFQSSummary 141
6.2 HFQSinLow-𝛽Cavities 142
6.3 DeconvolutionofR andR 143
BCS res
6.4 DepthofBakingEffect 145
6.4.1 FromAnodization 145
6.4.2 FromHFRinsing 145
6.4.3 DepthofMagneticFieldPenetrationbyLE-μSR 145
6.5 RoleoftheOxideLayerandRoleofN-Infusion 148
6.6 SIMSStudiesofO,H,andOHProfiles 151
6.7 HydrogenPresenceinHFQS 156
6.8 TEMStudiesonHydrides 158
6.9 Niobium–hydrogenPhaseDiagram 160
6.10 HEnrichmentatSurface 161
6.11 Q-diseaseReview 163
6.12 VisualizingNiobiumHydrides 165
6.12.1 Cold-stageConfocalMicroscopy 165
6.12.2 Cold-stageAtomicForceMicroscopy(AFM) 166
6.13 ModelforHFQS–ProximityEffectBreakdownofNano-hydrides 168
6.13.1 BakingBenefitandProximityEffectModel 170
6.14 PositronAnnihilationStudiesofHFQSandBakingEffect 172
6.15 PointContactTunnelingStudiesofHFQSandBakingEffect 173
7 QuestforHigherGradients:Two-StepBakingand
N-Infusion 175
7.1 Two-StepBaking 175
7.2 SubtleEffectsofTwo-StepBaking–Bifurcation 175
7.2.1 BifurcationReduction 177
∘
7.3 N-Infusionat120 C 181
7.4 N-InfusionatMediumTemperatures 184
7.5 UnifyingQuenchFields 188
7.6 QuenchDetectionbySecondSoundinSuperfluidHelium 190
8 ImprovementsinCavityPreparation 193
8.1 ComparisonsofColdandWarmElectropolishingMethods 193
8.2 ChemicalSoaking 197
8.3 OpticalInspectionSystemandDefectsFound 199
8.4 RoboticsinCavityPreparation 200
8.5 PlasmaProcessingtoReduceFieldEmission 201
9 PursuitofHigherPerformancewithAlternateMaterials 207
9.1 NbFilmsonCuSubstrates 207
9.1.1 DirectCurrentMagnetronSputtering 209
viii Contents
∘
9.1.2 DC-biasDiodeSputteringatHighTemperature(400–600 C) 209
9.1.3 SeamlessCavityCoating 210
9.1.4 Nb–CuFilmsbyECR 211
9.1.5 Nb–CuFilmsviaHigh-PowerImpulseMagnetronSputtering
(HIPIMS) 212
9.2 AlternativestoNb 214
9.2.1 Nb Sn 215
3
9.2.2 MgB 217
2
9.2.3 NbNandNbTiN 221
9.3 Multilayers 222
9.3.1 SIS’Structures 222
9.3.2 TheoreticalEstimates 223
9.3.3 Results 223
9.3.4 SS’Structures 225
9.4 Summary 227
PartIV Applications 229
10 NewCavityDevelopments 231
10.1 CrabCavitiesforLHCHighLuminosity 231
10.2 Short-PulseX-Rays(SPX)SystemfortheAPSUpgrade 238
10.3 QWRCavityforAcceleration 239
10.4 TravelingWaveStructureDevelopment 241
11 OngoingApplications 245
11.1 Overview 245
11.2 Low-BetaAcceleratorsforNuclearScienceandNuclear
Astrophysics 246
11.2.1 ATLASatArgonne 246
11.2.2 ISACandISAC-IIatTRIUMF 247
11.2.3 SPIRALIIatGANIL 247
11.2.4 HIEISOLDE 248
11.2.5 RILACatRIKEN 249
11.2.6 SPESUpgradeofALPIatINFN 249
11.2.7 FRIBatMSU 250
11.2.8 RAON 253
11.2.9 SpokeResonatorStructureDevelopmentstoAvoidMultipacting 254
11.2.10 JAEAUpgrade 255
11.2.11 HELIAC 256
11.2.12 SARAF 259
11.2.13 HIAFatIMP 259
11.2.14 IFMIF 260
11.3 High-IntensityProtonAccelerators 260
11.3.1 SNS 260