Persistent Current HTS Magnet Cooled by Cryocooler (2)—Magnet Configuration and Persistent Current Operation Test

Kusada, S.; Igarashi, M.; Kuwano, K.; Nemoto, Kaoru; Hirano, Satoshi; Okutomi, T.; Terai, Motoaki; Kuriyama, T.; Tasaki, Kenji; Tosaka, Taizo; Marukawa, K.; Hanai, S.; Yamashita, Tomohisa; Yanase, Y.; Nakao, Hiroyuki; Yamaji, M.

doi:10.1109/tasc.2005.849632

Cited by 17 publications

(3 citation statements)

References 2 publications

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“…The most important point in making a persistent-current HTS coil is using a good wire and careful manufacturing because defects or damages to the wire would have a negative effect on the current decay rates in the persistent current mode [5], [6]. Table I shows the specifications of the HTS coil.…”

Section: A Hts Coilmentioning

confidence: 99%

Development of Persistent-Current Mode HTS Coil for the RT-1 Plasma Device

Tosaka

Ohtani

Ono

et al. 2006

IEEE Trans. Appl. Supercond.

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The plasma confinement device "RT-1" which had a high temperature superconducting (HTS) floating magnet was constructed for advanced high-beta plasma and fusion research at the University of Tokyo. The high temperature superconducting (HTS) floating magnet is magnetically levitated inside the plasma vacuum vessel. Plasma is confined by a magnetic dipole field around the HTS floating magnet. The HTS floating magnet is operated in persistent-current mode and it consists of an HTS coil, an HTS persistent-current switch (PCS), a pair of demountable joints of current leads, detachable joints of a cooling tube, a thermal shield and a vacuum vessel. The HTS coil and the PCS and the thermal shield are cooled below 20 K by a flow of helium gas through the cooling tube. The floating HTS magnet is designed to operate in the temperature range from 20 K to 30 K without being cooled while it is levitated. We fabricated a persistent-current HTS coil that consists of the HTS coil and the PCS. Persistent-current operations and protection tests were conducted with the persistent-current HTS coil before it was mounted in the floating magnet cryostat. The current-decay rate was 0.9% in an 8 hour operation. The coil energy was safely discharged by inducing PCS quench in a protection test.

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Section: A Hts Coilmentioning

confidence: 99%

Development of Persistent-Current Mode HTS Coil for the RT-1 Plasma Device

Tosaka

Ohtani

Ono

et al. 2006

IEEE Trans. Appl. Supercond.

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“…The PCM operation provides the HTS magnet with advantages of: (a) less refrigerant consumption and higher thermal stability due to elimination of the heat leakage through current leads [1][2][3][4]; (b) robustness against unexpected power-off conditions [2,4]; (c) higher flexibility due to elimination of the cumbersome power source while running [4,5]; (d) possibility to generate a more stable DC magnetic field than the driven mode [2,6]. Therefore, PCM coils are desired in some energy storage systems [7,8], a few NMR/MRI projects [2,6,9,10] and most practically, the on-board magnets of maglev train systems [4,[11][12][13][14][15], which require high flexibility, safe off-power operation and efficient refrigeration. One of the major challenges concerning the PCM is that the persistent DC current circulating in the HTS coil would decay when exposed to AC fields due to the DC resistance generated in the superconductor, as illustrated by figure 1.…”

Section: Introductionmentioning

confidence: 99%

Study of the demagnetization behavior of no-insulation persistent-current mode HTS coils under external AC fields by 3D FEM simulation

Zhong,

Wu,

et al. 2024

Supercond. Sci. Technol.

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The no-insulation (NI) winding technique is promising to be applied in the persistent-current mode (PCM) operation of high-temperature superconducting (HTS) coils to provide those advantages. To apply the NI PCM coil, its demagnetization behaviour (i.e., decay of persistent DC current) by external AC field, which occurs in maglev trains, electric machines, and other dynamic magnet systems, is essential to be understood. For this purpose, a 3D FEM model, capturing the full electromagnetic properties of NI HTS coils, is established. This work has studied three kinds of AC fields, observing the impact of turn-to-turn contact resistivity on demagnetization rates, which is attributed to current distribution modulations. Under transverse AC field, the lower contact resistivity attracts more transport current to flow in the radial pathway to bypass the ‘dynamic resistance’ generated in the superconductor, leading to slower demagnetization. Under axial AC field, the demagnetization rate exhibits a non-monotonic relation with the contact resistivity: (1) the initial decrease of contact resistivity leads to concentration of induced AC current on the outer turns, which accelerates the demagnetization; (2) the further decrease of contact resistivity makes the current smartly redistribute to avoid to flow through the loss-concentrated outer turns, thus slowing down the demagnetization. Under the rotating DC field, a hybrid of the transverse and axial fields, the impact of contact resistivity on the demagnetization rate exhibits combined characteristics of the transverse and axial components. Besides, quantitative prediction on the demagnetization rate of NI PCM coil under external AC field is instructive for practical designs and operations, which is tried by this 3D FEM model, and a comparison with experimental result is conducted.

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“…For MRI and NMR, the magnetic field decay rate must be at most 0.05 ppm h −1 , and hence joint resistance at pico-ohm level is required [5,6]. Even for cases such as maglev, in which the decay rate limit is 1%/day [7][8][9][10], and joint resistance at the nano-ohm level is a basic requirement. Superconducting joints of 2G-HTS tapes have been achieved in recent years [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

An equivalent homogenized model for non-superconducting joints made by ReBCO coated conductors

Pan¹,

Wu²,

Sheng³

et al. 2018

Supercond. Sci. Technol.

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The most popular method of reducing joint resistance R j is by increasing overlap length l. A numerical model capable of simulating the relationship between joint resistance and overlap length (the log(R j )-log(l) curve) could provide guidance for commercial high temperature superconducting joint manufacturing and may shed light on some more detailed behavior. In this study, a threedimensional model with an equivalent single homogeneous layer, characterized by resistance per unit area ρ s (Ω m 2 ), is developed and tested against experimental data. With this model, detailed measurement of parameters such as the thickness and resistivity of each layer and the interfacial resistance are not necessary. The log(R j )-log(l) relationship, especially for longer joints (l>20 cm), can be predicted by employing only ρ s , which can be experimentally and accurately obtained from shorter joints (l20 cm). The log(R j )-log(l) curve exhibits a nonlinear relationship when the overlap length exceeds a certain threshold value, in contrast to the commonly considered R j =ρ s /wl relationship (where w is the width of the joining area). This result is validated by accurately measuring the resistance of soldered joints with overlap lengths of 5-90 cm. The sensitivity of simulation results by different n values, I j /I c , and meshing precision levels are also presented.

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Persistent Current HTS Magnet Cooled by Cryocooler (2)—Magnet Configuration and Persistent Current Operation Test

Cited by 17 publications

References 2 publications

Development of Persistent-Current Mode HTS Coil for the RT-1 Plasma Device

Development of Persistent-Current Mode HTS Coil for the RT-1 Plasma Device

Study of the demagnetization behavior of no-insulation persistent-current mode HTS coils under external AC fields by 3D FEM simulation

An equivalent homogenized model for non-superconducting joints made by ReBCO coated conductors

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