Magnetization, AC Loss, and Quench in YBCO Cables” Basic Research Magnetization, AC Loss, and Quench in YBCO Cables”

Mike Sumption, M. Majoros, C. Myers, and E.W. Collings Modelling and Measurement of Magnetization of YBCO CORC and Roebel Cables for Accelerators CORC Samples: D. Van Der Laan Advanced Conductor Technologies and University of Colorado Twisted Strand: University of Houston Mike Sumption, M. Majoros, C. Myers, and E.W. Collings Center for Superconducting and Magnetic Materials, MSE, The Ohio State University NAVY Applied Superconductivity Workshop, April 2016 This work was supported by the U.S. Department of Energy, Office of Science, Division of High Energy Physics, under Grant DE-SC0011721 and an AF Summer Faculty

OSU Magnetization Rigs Magnetization Measurement Facilities: A number of options are available, some systems better suited to given samples or given test requirements

MAG-0: 14 T, 2K-RT PPMS Quantum Design Physical Property Measuring System (PPMS) equipped with a 14 T superconducting magnet and temperature control from 1.8 K to 400 K, can measure: M-H, AC susceptibility, AC transport, DC transport, Thermal conductivity, Hall effect, Heat capacity. Used to measure Nb3Sn M-H loops and magnetizations, as well as those of Bi:2212 strand

MAG-1: 4.2 K, +- 12 T Magnetization rig MAG-1, for samples larger than can be measured in the PPMS, but smaller than use for MAG-2. This is a susceptibility rig type magnetometer inside of a 12 T cryocooled magnet. Inside the 3” diameter room temperature bore is a varitemp dewar with a magnetization insert (b) side view, (c) face view. A current of up to 200 A can be applied to samples which are being measured for M-H. Figure A6.2. Magnetization rig MAG-1, for samples larger than can be measured in the PPMS, but smaller than use for MAG-2. This is a susceptibility rig type magnetometer inside of a 12 T cryocooled magnet. Inside the 3” diameter room temperature bore is a varitemp dewar with a magnetization insert (b) side view, (c) face view. A current of up to 200 A can be applied to samples which are being measured for M-H.

MAG-2 a (d) b c Cable Magnetization measuring facility (Magnet arrived early Feb 2016, assembly underway); 3 T coil (Cryomagnetics design and made), NbTi wound, 150 amperes, Inductance of 10 milliHenries. Clear bore is 5.5 cm total length 30.48 cm. Drawing of coils, homogeneity on-axis is +/- 5% over 15 cm, radial field homogeneity.

3 T Magnet Max Field = 3.1 T Max I = 90 A L = 1 H Max Ramp Rate = 70 mT/s

MAG-3: Screening loss rig M-H and AC Loss device for 77 K measurements of YBCO, with typical sample shown above (YBCO CORC cable in this case). External-Field M-H and AC Loss is measured in the applied fields of copper wound solenoids and race-track coils of various sizes. A system of pick-up coils connected to a digital oscilloscope records the samples' M-H loops Used in this program for screening and as a comparison/calibration measurement at 77 K Also 77 K, SF is like 20 T, 4 K

hysteretic YBCO CORC cable losses tape CORC cable from Tape Penetration field increases for cables made from tapes– a shielding effect Complicated helical geometries

SAM-AC Loss A radial and tangential field is generated The field is approximately sinusoidal We can measure samples as small as a cm segment of tape, as well as lengths of cable and small coils The system can apply a field of 0.5 T at 13600 RPM and 540 T/s Shown below is a 10 cm segment of 4 mm wide tape Bmax = 0.56 T Here we have a comparison to solenoidal measurement

SAM-CORC The hysteretic loss and magnetization of CORC above field penetration can be approximated by Tape loss * 2/ If we consider a helically wrapped tape, then some of the time, B  tape Sometimes, B // tape Average B  tape is 2/ Then can we estimate AC loss and mag of CORC by tape*2/? Bmax = 0.56 T As measured CORC * /2

Measurements on CORC at 77 K Of interest: Magnetization of striated tape Magnetization of striated and twisted tape Magnetization of striated and unstriated tapes on CORC Re-estimate of error field estimates

Measured Loss in Striated and Twisted YBCO– University of Houston tape samples Un-Striated Striated Striated and Twisted width = 12 mm length = 16.1 cm Thickness = 70 µm

YBCO, Striping, Twisting Sample 1: Striated Sample 2: Not Striated Sample 3: Striated and Twisted Measurements made on University of Houston Samples 50 Hz, Bmax = 0.1 T Striations + Twisting needed for magnetization reduction

Striated measurement results 77 K Striations do significantly reduce loss Some factor from striation, some from Ic loss

FEM Modelling Initial approach Model to start as model of one helix, then moving to multiples Treat the SC film as distributed Jc values are representative of 4 K, 0 T

Modelling Treatment Composite, 250 m SC, 1 m Substrate, 50 m Penetration field, Bp = CJcd So, only OK if re-normalization is in same dimension as d M = CJcd Msc = msc/Vsc= CJcd Let Je=Jc/ff Mcomp = Msc/Vcomp = Msc/(Vsc*ff)=mscJcd/ff=mscCJed So we can treat the current as flowing through the whole composite and get a proper M

Calculation for 1 strand CORC cable (4K)

Comparison loss shape to model AC loss of sample R3 at 50 Hz in liquid nitrogen bath (77 K) FEM model prediction

Summary Various magnetization rigs are in operation and also commissioning Under construction – 3 T, 4 K AC loss rig capable of 25 cm YBCO cable samples Magnetization measurement, modelling, and comparison to accelerator targets underway Measurements of Striated CORC cables show significant magnetization Reduction Measuring of Twisted striated samples (With UoH) show magnetization suppression, as expected