1. C.J. Kovacs M.D. Sumption E.W. Collings M. Majoros X. Xu X. Peng
Stability measurements in Nb3Sn strands with various wire and sub-element diameters
The Ohio State University
C.J. Kovacs
M.D. Sumption
E.W. Collings
M. Majoros
X. Xu
Hyper Tech Research, Inc.
X. Peng

2. Acknowledgements
This work was supported by the U.S. Department of Energy, High Energy Physics university grant DE-FG02- 95ER4090 as well as a State of Ohio program

3. Background
Nb3Sn superconducting strands are the likely canditate for next generation: [1]
large-scale high-field applications
LHC luminosity upgrade
some undulator and wiggler magnets.
Low-fields magneto-thermal instabilities limiting application performance.
Two types of co-existing characters:
self-field
magnetization-type.
RRR, Deff, strand diameter, and Jc. [2, 3]
A. Zlobin, APT Seminar 2008 : Nb3Sn Accelerator
Magnet R&D and LHC Luminosity Upgrades
M.D. Sumption et al. Cryogenics
M.D. Sumption Adv. Cryo. Eng. ICMC Vol. 56 CP
B. Bordini, L. Rossi IEEE Trans. App. Supercond. Vol. 19 No. 3 June 2009

4. Motivation/Procedure
Instabilities measured on single-strands mounted using ITER barrels  lead to difficulties in magnets. [2]
V-I and V-H and Stability current measured for samples with varying RRR, Deff, strand diameter, and Jc (varying reaction)
V-I 0.2 A/s near transition
0-2 Tesla V-B*
I-ramp 1 A/s
B-ramp 1 T/min
*One sample 0-3T

5. Strand Parameters

6. Sample Parameters Range Deff: 20-87µm RRR: 8-91 Strand Dia: 0.5-0.84mm
12 Jc: A/mm2
Twist Pitch: 15mm

7. Stability Data
12T Jc= 2908 A/mm2
12T Jc= 743 A/mm2

8. Stability Data
12T Jc= 1547 A/mm2
12T Jc= 1178 A/mm2

9. Stability Data
12T Jc= 1840 A/mm2
12T Jc= 1267 A/mm2

10. Stability Data
12T Jc= 1544 A/mm2
12T Jc= 1727 A/mm2

11. Stability Data
12T Jc= 2067 A/mm2
12T Jc= 1494 A/mm2

12. Stability Data
12T Jc= 1317A/mm2
12T Jc= 1379 A/mm2

13. Stability Data
12T Jc= 1271 A/mm2
0-3T
12T Jc= 1614 A/mm2

14. Stability Data Correlations

15. Stability Data Correlations

16. Stability Data Correlations

17. Stability Data Correlations
Deff React
Deff-react/Deff ≈ 1
Deff-react/Deff < 1

18. Stability Data Correlations

19. Conclusions/Future Work
Clear inverse relationship between Deff and Js
Better fit with Deff-react
Of course RRR, Strand Diameter also important – dependence less pronounced for this data set
Measure additional Tube and RIT-type strands
Compare to stability models proposed by Sumption and Bordini-Rossi.