Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor
Recent advances in the performance and manufacturing of high-temperature superconductors (HTS) such as rare earth barium copper oxide (REBCO) are enabling a new generation of large-scale superconducting magnets operating at magnetic fields in excess of 20 T. Characterizing REBCO tape current as a fu...
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| Format: | Thesis |
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Massachusetts Institute of Technology
2023
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| Online Access: | https://hdl.handle.net/1721.1/150102 |
| _version_ | 1811096369357651968 |
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| author | Tang, Kevin |
| author2 | Hartwig, Zachary S. |
| author_facet | Hartwig, Zachary S. Tang, Kevin |
| author_sort | Tang, Kevin |
| collection | MIT |
| description | Recent advances in the performance and manufacturing of high-temperature superconductors (HTS) such as rare earth barium copper oxide (REBCO) are enabling a new generation of large-scale superconducting magnets operating at magnetic fields in excess of 20 T. Characterizing REBCO tape current as a function of temperature (T), magnetic field (B), and magnetic field angle (ϕ) is an essential activity for providing magnet design and operational data as well as for quality control; however, the high critical current of REBCO make such characterization difficult. To overcome this issue, a process called bridging is frequently employed such that a well-defined subsection of the tape width is used as a proxy for the full width REBCO tape. The benefit is that the total current required for characterization scales with the subsection width, enabling accurate, simpler, and more accessible characterizations, especially at high performance. Two downsides are the traditional bridge manufacturing process and the potential for the bridge to sample regions of higher or lower than width-averaged critical current.
Bridging is traditionally achieved through a process of chemical etching and photolithography, which is labor and time-intensive, can inadvertently damage the superconductor if the REBCO coatings are thick, and can only be done on specially prepared REBCO samples without copper surface layers instead of the commercially manufactured tapes used in actual magnets [1]. To improve upon this method, this thesis proposes and qualifies a laser-based microbridging technique known as skiving, in which a precision laser is used to cut an optimized subsection of REBCO for accurate critical current characterization at significantly reduced test currents. From the fundamental power law describing superconductivity, the critical current and power law index (the so-called “n-value”) were the two main parameters used in assessing the performance of the technique and microbridge designs [2]. Bridges were tested at the MIT Plasma Science and Fusion Center (77 K, self-field), Commonwealth Fusion Systems (15 K - 77 K, self-field - 12 T), and at the High Field Laboratory for Superconducting Materials (HFLSM) at Tohoku University in Japan, where the 40 𝜇m bridges were exposed to the most extreme conditions (4 K - 50 K, 0 T - 20 T) over two research campaigns in October 2019 and January 2020.
400 µm single channel bridges were created and upon testing, produced an average post-bridge to pre-bridge n-value ratio of 0.67 ± 0.01 and an average bridge efficiency of 0.99 ± 0.01, serving as the baseline for subsequent tests. Different designs were tested to capture as much of the tape width as possible and provide a more accurate prediction of the full width critical current at very small (down to 40 µm) bridge widths, resulting in two variations that achieved an average n-value ratio of 0.64 ± 0.01 and an efficiency of 0.88 ± 0.01, providing good confidence in the use of such bridges to characterize full width tape. 40 µm bridges were shown to be significantly more accurate than chemically etched bridges in testing at the HFLSM and key lessons about what to include and exclude in bridge designs were learned. Future work is recommended for further investigation into characterizing samples from different manufacturers with varying layer thicknesses as well as improving the accuracy and robustness of the bridges in predicting full-width REBCO tape performance. |
| first_indexed | 2024-09-23T16:42:43Z |
| format | Thesis |
| id | mit-1721.1/150102 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T16:42:43Z |
| publishDate | 2023 |
| publisher | Massachusetts Institute of Technology |
| record_format | dspace |
| spelling | mit-1721.1/1501022023-11-09T07:56:29Z Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor Tang, Kevin Hartwig, Zachary S. Massachusetts Institute of Technology. Department of Nuclear Science and Engineering Recent advances in the performance and manufacturing of high-temperature superconductors (HTS) such as rare earth barium copper oxide (REBCO) are enabling a new generation of large-scale superconducting magnets operating at magnetic fields in excess of 20 T. Characterizing REBCO tape current as a function of temperature (T), magnetic field (B), and magnetic field angle (ϕ) is an essential activity for providing magnet design and operational data as well as for quality control; however, the high critical current of REBCO make such characterization difficult. To overcome this issue, a process called bridging is frequently employed such that a well-defined subsection of the tape width is used as a proxy for the full width REBCO tape. The benefit is that the total current required for characterization scales with the subsection width, enabling accurate, simpler, and more accessible characterizations, especially at high performance. Two downsides are the traditional bridge manufacturing process and the potential for the bridge to sample regions of higher or lower than width-averaged critical current. Bridging is traditionally achieved through a process of chemical etching and photolithography, which is labor and time-intensive, can inadvertently damage the superconductor if the REBCO coatings are thick, and can only be done on specially prepared REBCO samples without copper surface layers instead of the commercially manufactured tapes used in actual magnets [1]. To improve upon this method, this thesis proposes and qualifies a laser-based microbridging technique known as skiving, in which a precision laser is used to cut an optimized subsection of REBCO for accurate critical current characterization at significantly reduced test currents. From the fundamental power law describing superconductivity, the critical current and power law index (the so-called “n-value”) were the two main parameters used in assessing the performance of the technique and microbridge designs [2]. Bridges were tested at the MIT Plasma Science and Fusion Center (77 K, self-field), Commonwealth Fusion Systems (15 K - 77 K, self-field - 12 T), and at the High Field Laboratory for Superconducting Materials (HFLSM) at Tohoku University in Japan, where the 40 𝜇m bridges were exposed to the most extreme conditions (4 K - 50 K, 0 T - 20 T) over two research campaigns in October 2019 and January 2020. 400 µm single channel bridges were created and upon testing, produced an average post-bridge to pre-bridge n-value ratio of 0.67 ± 0.01 and an average bridge efficiency of 0.99 ± 0.01, serving as the baseline for subsequent tests. Different designs were tested to capture as much of the tape width as possible and provide a more accurate prediction of the full width critical current at very small (down to 40 µm) bridge widths, resulting in two variations that achieved an average n-value ratio of 0.64 ± 0.01 and an efficiency of 0.88 ± 0.01, providing good confidence in the use of such bridges to characterize full width tape. 40 µm bridges were shown to be significantly more accurate than chemically etched bridges in testing at the HFLSM and key lessons about what to include and exclude in bridge designs were learned. Future work is recommended for further investigation into characterizing samples from different manufacturers with varying layer thicknesses as well as improving the accuracy and robustness of the bridges in predicting full-width REBCO tape performance. S.M. 2023-03-31T14:32:11Z 2023-03-31T14:32:11Z 2023-02 2023-03-08T20:16:21.426Z Thesis https://hdl.handle.net/1721.1/150102 In Copyright - Educational Use Permitted Copyright MIT http://rightsstatements.org/page/InC-EDU/1.0/ application/pdf Massachusetts Institute of Technology |
| spellingShingle | Tang, Kevin Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor |
| title | Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor |
| title_full | Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor |
| title_fullStr | Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor |
| title_full_unstemmed | Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor |
| title_short | Evaluation of Novel Laser-Skived Microbridges for Improved Characterization of REBCO Superconductor |
| title_sort | evaluation of novel laser skived microbridges for improved characterization of rebco superconductor |
| url | https://hdl.handle.net/1721.1/150102 |
| work_keys_str_mv | AT tangkevin evaluationofnovellaserskivedmicrobridgesforimprovedcharacterizationofrebcosuperconductor |