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

2. 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-SC and an AF Summer Faculty

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

4. 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

5. MAG-1: 4.2 K, 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.

6. 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 cm.
Drawing of coils, homogeneity on-axis is +/- 5% over 15 cm,
radial field homogeneity.

7. 3 T Magnet Max Field = 3.1 T Max I = 90 A L = 1 H
Max Ramp Rate = 70 mT/s

8. 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

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

10. 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 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

11. 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

12. 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

13. 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

14. 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

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

16. 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

17. 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

18. Calculation for 1 strand CORC cable (4K)

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

20. 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