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R&D of fundamental technologies of accelerator magnets using coated conductors N. Amemiya, Z. Zhang, T. Sano, Y. Sogabe, T. Nakamura (Kyoto Univ.)T. Ogitsu (KEK), K. Koyanagi, S. Takayama, T. Kurusu (Toshiba)Y. Mori (KURRI), Y. Iwata, K. Noda (NIRS), M. Yoshimoto (JAEA)The 2014 Kyoto Workshop on HTS Magnet Technologyfor High Energy Physics(WAMHTS-2)November 13 14, 2014Kyoto, JapanThis work was supported by Japan Science and Technology Agency under Strategic Promotion of Innovative Research and Development Program (S-Innovation Program).1OutlineOverview of the S-Innovation Project on R&D of fundamental technologies of accelerator magnets using coated conductorsAs a topic: study on magnetization of coated conductor and field quality2N. Amemiya, WAMHTS-2, Nov. 14, 20143N. Amemiya, WAMHTS-2, Nov. 14, 2014Overview of the S-Innovation Project3Outline the project4N. Amemiya, WAMHTS-2, Nov. 14, 2014Name of projectChallenge to functional, efficient, and compact accelerator system using high Tc superconductorsObjectiveR&D of fundamental technologies for accelerator magnets using coated conductorsConstructing and testing prototype magnetFuture applicationsCarbon caner therapyAccelerator-driven subcritical reactorParticipating institutionsKyoto University, Toshiba, KEK, NIRS (National Institute of Radiological Sciences), JAEAPeriodStage I: 01/2010 03/2012Stage II: 04/2012 03/2016Stage III: 04/2016 03/2019Funding programStrategic Promotion of Innovative Research and Development (S-Innovation) Program by JSTKey issues in R&DHTS magnet design which is compatible with accelerator designWinding technology for negative-bend coils and 3D shape coils to realize the designed magnetsTape magnetization which affects the field quality of magnets5N. Amemiya, WAMHTS-2, Nov. 14, 2014Stage I and II: to establish fundamental technologyProject overview and key R&D issues at stage I & II6N. Amemiya, WAMHTS-2, Nov. 14, 2014Accelerator(Carbon therapy, ADSR)MagnetFieldmeasurementSimulation technologyMagnetization and field qualityWinding technologiesDesign studyPrediction / correctionModel magnetStage III: to demonstrate function of beam guidingPrototype magnet3D windingNegative-bend windingMagnet designSpiral sector FFAG accelerator for carbon cancer therapy7N. Amemiya, WAMHTS-2, Nov. 14, 2014Radial magnetic field distributionFFAG accelerator: strong focusing with dc magnetTypeSpiral sectorPurposeCarbon cancer therapyParticleC+6Energy40 - 400 MeV/uMajor radius4.65 mAverage orbit radius3.8 5.5 mField index (k value)5.7Integrated field at r = 5.5 m3.98 TmSpiral angle58.4 degNumber of cell10Packing factor0.5

Magnet designSpiral sector FFAG accelerator for carbon cancer therapy8N. Amemiya, WAMHTS-2, Nov. 14, 2014Preliminary estimationWeight of iron ~ 60 t; stored energy ~ 2 3 MJ; B @ conductor ~ 7 8 T

Radial profile is provided by ladder shape coils.Field with spiral angle is provided by coils with negative bend and iron.

Winding technology R&DExamples of test winding9N. Amemiya, WAMHTS-2, Nov. 14, 2014

350 mm240 mm

Model magnet to verify developed technologies10N. Amemiya, WAMHTS-2, Nov. 14, 2014

Coils are put in cryostat and cooled by using GM cryo-coolerIron is placed at room temperatureMagnetic field distribution will be measured by using scanning Hall probe and rotating pick-up coils11N. Amemiya, WAMHTS-2, Nov. 14, 2014Study on magnetization ofcoated conductor and field qualityContent of this partMagnetic field harmonics measurements in small dipole magnetsComparisons with 2D electromagnetic field analyses3D model for electromagnetic field analyses to evaluate magnetic field harmonicsPerspective: how to manage this issue12N. Amemiya, WAMHTS-2, Nov. 14, 201413N. Amemiya, WAMHTS-2, Nov. 14, 2014Magnetic field harmonics measurements13Tested magnets14N. Amemiya, WAMHTS-2, Nov. 14, 2014RTC4-FRTC2-FRTC4-SPNumber of racetrack coils424Inner / outer width of racetrack96 mm / 152.8 mm80 mm / 132 mm96 mm / 134 mmLength of straight part250 mm250 mm250 mmNumber of turn83 turns/coil76.5 turns/coil108 turns/coilSeparation between pole58 mm52.8 mm56.2 mmCoated conductorFYSC-SC05FYSC-SC05SCS4050CoolingLN2GM cryocoolerGM cryocoolerDipole field0.088 T @50 A0.5 T @200 AConductor field0.23 T @50 A1.45 T @200 A

RCT-4, LN2, experimental setup, typical data15N. Amemiya, WAMHTS-2, Nov. 14, 2014

RCT-4, LN2, 2D electromagnetic field analyses16N. Amemiya, WAMHTS-2, Nov. 14, 2014

RTC4-SP, GM cryocooler, drifts in dipole and sextupole17N. Amemiya, WAMHTS-2, Nov. 14, 2014

200 A, 3 hour @20 K

Drift in dipole8.9 10-4Drift in sextupole0.72 10-4RTC4-SP, GM cryocooler, temperature dependence18N. Amemiya, WAMHTS-2, Nov. 14, 2014100 A, 3 hour @20 KDrift in 3 hoursDipole: 1.4 10-4 Sextupole: 0.22 10-4 Drift in 3 hoursDipople: 5.5 10-4 Sextupole: 0.60 10-4 100 A, 3 hour @30 K

RTC4-SP, GM cryocooler, field (current) dependence19N. Amemiya, WAMHTS-2, Nov. 14, 2014Drift in 3 hoursDipole: 1.4 10-4 Sextupole: 0.22 10-4 Drift in 3 hoursDipople: 8.9 10-4 Sextupole: 0.72 10-4 200 A (1.45 T @conductor) 3 hour @20 K

100 A (0.725 T @conductor) 3 hour @20 K20N. Amemiya, WAMHTS-2, Nov. 14, 20143D model forelectromagnetic field analysesto evaluate magnetic field harmonics20Flared-end racetrack coils21N. Amemiya, WAMHTS-2, Nov. 14, 2014

A cosine-theta dipole magnet for rotating gantry for carbon cancer therapy22N. Amemiya, WAMHTS-2, Nov. 14, 2014

1st turn in 1st layer

Multi-pole coefficientsAnalyzed value(with magnetization)Uniform currentcontribution of magnetization6 pole100.12491.504 8.620 10 pole9.6117.2772.334 14 pole1.064 1.0130.051 Analysis of 1st layer only23N. Amemiya, WAMHTS-2, Nov. 14, 2014Perspective23How to manage this issue?We have to accept the existence of the large magnetization in coated conductors.A good news: reproducible magnetization3D modeling will enable us the magnetic field design considering the magnetization: at least if the magnetization current is stable and hardly decays, we can design a coil which can generate the required magnetic field, not assuming uniform current but considering the calculated not uniform current distribution with magnetization current.Drift in harmonics caused by the decay of magnetization must be a more serious issue.Another good news: Not very large drift: at the order of unit, most possibly less than 10 unitsDipole drifting more but higher harmonics drifting lessLess drifts at lower temperature

24N. Amemiya, WAMHTS-2, Nov. 14, 201425N. Amemiya, WAMHTS-2, Nov. 14, 2014Back-up slidesDipole magnet RTC4-F comprising race-track coils 26N. Amemiya, WAMHTS-2, Nov. 14, 2014Coated conductorFujikura (FYSC-SC05)SuperconductorGdBCOWidth thickness5 mm 0.2 mmStabilizer0.1 mm thick copperCritical current270 A 298 A

Shape of coilsSingle pancake race-trackNumber of coils4Length of straight section250 mmInner radius at coil end48 mmOuter radius at coil end76.4 mmCoil separation58 mmNumber of turns83 turn/coilLength of conductor74 m/coil

Ic ~ 110 AEquation for analyses27

Equivalent conductivity derived from power law characteristic

Faradays law

Biot-Savarts law

Definitional of current vector potential

Thin strip approximationNeglecting current density component normal to SC layer / magnetic flux density component tangential to SC layerTransformed to 2D problemN. Amemiya, WAMHTS-2, Nov. 14, 201427Consideration of three-dimensional geometry of coated conductors in a coil28N. Amemiya, WAMHTS-2, Nov. 14, 2014

r : vector from the source point where the current resides to the field point where the potential is calculated.Superconductor layers are mathematically two-dimensional (no thickness), but follow the curved geometry of coated conductors in a coil.

The three-dimensional geometry of the coil is retained in the modeling, while region of analysis is mathematically two-dimensional.