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

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

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 52 91-99 2012 M.D. Sumption Adv. Cryo. Eng. ICMC Vol. 56 CP1219 2010 B. Bordini, L. Rossi IEEE Trans. App. Supercond. Vol. 19 No. 3 June 2009

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

Strand Parameters

Sample Parameters Range Deff: 20-87µm RRR: 8-91 Strand Dia: 0.5-0.84mm 12 Jc: 743-2908 A/mm2 Twist Pitch: 15mm

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

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

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

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

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

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

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

Stability Data Correlations

Stability Data Correlations

Stability Data Correlations

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

Stability Data Correlations

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.