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Title: Validation of Finite-Element Models of Persistent-Current Effects in Nb 3Sn Accelerator Magnets

Abstract

Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb 3Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnet designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed.

Authors:
 [1];  [2];  [2];  [3];  [1];  [2];  [1];  [4];  [1];  [1];  [1];  [1];  [1];  [3];  [2];  [3];  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
  3. The Ohio State Univ., Columbus, OH (United States)
  4. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
The Ohio State Univ., Columbus, OH (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1213937
Grant/Contract Number:  
AC02-07CH11359; AC02-98CH10886; AC02-05CH11231; AC02-76SF00515; SC0010312
Resource Type:
Accepted Manuscript
Journal Name:
IEEE Transactions on Applied Superconductivity
Additional Journal Information:
Journal Volume: 25; Journal Issue: 3; Journal ID: ISSN 1051-8223
Publisher:
Institute of Electrical and Electronics Engineers (IEEE)
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 36 MATERIALS SCIENCE; Nb3Sn, magnetization, accelerator

Citation Formats

Wang, X., Ambrosio, G., Chlachidze, G., Collings, E. W., Dietderich, D. R., DiMarco, J., Felice, H., Ghosh, A. K., Godeke, A., Gourlay, S. A., Marchevsky, M., Prestemon, S. O., Sabbi, G., Sumption, M. D., Velev, G. V., Xu, X., and Zlobin, A. V. Validation of Finite-Element Models of Persistent-Current Effects in Nb3Sn Accelerator Magnets. United States: N. p., 2015. Web. doi:10.1109/TASC.2014.2385932.
Wang, X., Ambrosio, G., Chlachidze, G., Collings, E. W., Dietderich, D. R., DiMarco, J., Felice, H., Ghosh, A. K., Godeke, A., Gourlay, S. A., Marchevsky, M., Prestemon, S. O., Sabbi, G., Sumption, M. D., Velev, G. V., Xu, X., & Zlobin, A. V. Validation of Finite-Element Models of Persistent-Current Effects in Nb3Sn Accelerator Magnets. United States. doi:10.1109/TASC.2014.2385932.
Wang, X., Ambrosio, G., Chlachidze, G., Collings, E. W., Dietderich, D. R., DiMarco, J., Felice, H., Ghosh, A. K., Godeke, A., Gourlay, S. A., Marchevsky, M., Prestemon, S. O., Sabbi, G., Sumption, M. D., Velev, G. V., Xu, X., and Zlobin, A. V. Tue . "Validation of Finite-Element Models of Persistent-Current Effects in Nb3Sn Accelerator Magnets". United States. doi:10.1109/TASC.2014.2385932. https://www.osti.gov/servlets/purl/1213937.
@article{osti_1213937,
title = {Validation of Finite-Element Models of Persistent-Current Effects in Nb3Sn Accelerator Magnets},
author = {Wang, X. and Ambrosio, G. and Chlachidze, G. and Collings, E. W. and Dietderich, D. R. and DiMarco, J. and Felice, H. and Ghosh, A. K. and Godeke, A. and Gourlay, S. A. and Marchevsky, M. and Prestemon, S. O. and Sabbi, G. and Sumption, M. D. and Velev, G. V. and Xu, X. and Zlobin, A. V.},
abstractNote = {Persistent magnetization currents are induced in superconducting filaments during the current ramping in magnets. The resulting perturbation to the design magnetic field leads to field quality degradation, in particular at low field where the effect is stronger relative to the main field. The effects observed in NbTi accelerator magnets were reproduced well with the critical-state model. However, this approach becomes less accurate for the calculation of the persistent-current effects observed in Nb3Sn accelerator magnets. Here a finite-element method based on the measured strand magnetization is validated against three state-of-art Nb3Sn accelerator magnets featuring different subelement diameters, critical currents, magnet designs and measurement temperatures. The temperature dependence of the persistent-current effects is reproduced. Based on the validated model, the impact of conductor design on the persistent current effects is discussed. The performance, limitations and possible improvements of the approach are also discussed.},
doi = {10.1109/TASC.2014.2385932},
journal = {IEEE Transactions on Applied Superconductivity},
number = 3,
volume = 25,
place = {United States},
year = {2015},
month = {1}
}

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