Inverse analysis of critical current density in a bulk high-temperature superconducting undulator

TY - JOUR

T1 - Inverse analysis of critical current density in a bulk high-temperature superconducting undulator

AU - Kinjo, Ryota

AU - Calvi, Marco

AU - Zhang, Kai

AU - Hellmann, Sebastian

AU - Liang, Xiaoyang

AU - Schmidt, Thomas

AU - Ainslie, Mark D.

AU - Dennis, Anthony R.

AU - Durrell, John H.

N1 - Funding Information: This work was done under the auspices of CHART (Swiss Accelerator Research and Technology Collaboration, ). M D Ainslie would like to acknowledge financial support from an Engineering and Physical Sciences Research Council (EPSRC) Early Career Fellowship, EP/P020313/1. All data are provided in full in the results section of this paper. R. K. would like to acknowledge his present institution, Institute of Advanced Energy, Kyoto University. The authors would like to thank Dr. Marek Bartkowiak from Paul Scherrer Institut for calibrating Hall sensors with PPMS. Publisher Copyright: © 2022 authors. Published by the American Physical Society.

PY - 2022/4/8

Y1 - 2022/4/8

N2 - In order to optimize the design of undulators using high-temperature superconductor (HTS) bulks we have developed a method to estimate the critical current density (Jc) of each bulk from the overall measured magnetic field of an undulator. The vertical magnetic field was measured along the electron-beam axis in a HTS bulk-based undulator consisting of twenty Gd-Ba-Cu-O (GdBCO) bulks inserted in a 12-T solenoid. The Jc values of the bulks were estimated by an inverse analysis approach in which the magnetic field was calculated by the forward simulation of the shielding currents in each HTS bulk with a given Jc. Subsequently the Jc values were iteratively updated using the precalculated response matrix of the undulator magnetic field to Jc. We demonstrate that it is possible to determine the Jc of each HTS bulk with sufficient accuracy for practical application within around 10 iterations. The precalculated response matrix, created in advance, enables the inverse analysis to be performed within a practically short time, on the order of several hours. The measurement error, which destroys the uniqueness of the solution, was investigated and the points to be noted for future magnetic field measurements were clarified. The results show that this inverse-analysis method allows the estimation of the Jc of each bulk comprising an HTS bulk undulator.

AB - In order to optimize the design of undulators using high-temperature superconductor (HTS) bulks we have developed a method to estimate the critical current density (Jc) of each bulk from the overall measured magnetic field of an undulator. The vertical magnetic field was measured along the electron-beam axis in a HTS bulk-based undulator consisting of twenty Gd-Ba-Cu-O (GdBCO) bulks inserted in a 12-T solenoid. The Jc values of the bulks were estimated by an inverse analysis approach in which the magnetic field was calculated by the forward simulation of the shielding currents in each HTS bulk with a given Jc. Subsequently the Jc values were iteratively updated using the precalculated response matrix of the undulator magnetic field to Jc. We demonstrate that it is possible to determine the Jc of each HTS bulk with sufficient accuracy for practical application within around 10 iterations. The precalculated response matrix, created in advance, enables the inverse analysis to be performed within a practically short time, on the order of several hours. The measurement error, which destroys the uniqueness of the solution, was investigated and the points to be noted for future magnetic field measurements were clarified. The results show that this inverse-analysis method allows the estimation of the Jc of each bulk comprising an HTS bulk undulator.

UR - http://www.scopus.com/inward/record.url?scp=85128707582&partnerID=8YFLogxK

U2 - 10.1103/PhysRevAccelBeams.25.043502

DO - 10.1103/PhysRevAccelBeams.25.043502

M3 - Article

AN - SCOPUS:85128707582

SN - 2469-9888

VL - 25

JO - Physical Review Accelerators and Beams

JF - Physical Review Accelerators and Beams

IS - 4

M1 - 043502

ER -