Waveform Control Pulse Magnetization for HTS Bulk With Flux Jump

Ida, Tetsuya; Li, Zhi; Miki, M.; Watasaki, Masahiro; Izumi, Mitsuru

doi:10.1109/tasc.2018.2816099

Cited by 18 publications

(14 citation statements)

References 11 publications

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“…The trapped field in a superconducting RE-Ba-Cu-O disc bulk can be enhanced by controlling the waveform of the magnetizing pulse used in the PFM method [14]. The waveform of the magnetizing pulses can be modified by changing the values of the capacitance, inductance or resistance of the pulse-generating circuit [15].…”

Section: Introductionmentioning

confidence: 99%

“…Alternatively, Hirano et al [13] increased the rise time of the magnetizing pulses by inserting copper plates into a stack of ring-shaped MgB 2 bulk superconductors. In a different approach, Ida et al [14,16] used the waveform control pulse magnetization (WCPM) method to modify the waveform of the magnetizing pulses. In this WCPM method, an Insulated Gate Bipolar Transistor (IGBT) was used, which acts as a high-speed switch.…”

Section: Introductionmentioning

confidence: 99%

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Waveform Control Pulsed Field Magnetization of RE-Ba-Cu-O Bulk Superconducting Rings

Tsui¹,

Moseley

Dennis³

et al. 2022

IEEE Trans. Appl. Supercond.

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One of the potential applications of ring-shaped, single grain RE-Ba-Cu-O bulk superconductors is in desktop magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) systems as an alternative to conventional permanent magnets. The higher magnetic field available from magnetized bulk superconductors could significantly improve the performance of such systems, as well as reduce their size and increase portability. The pulsed field magnetization (PFM) method provides a fast, compact and cost-effective method for magnetizing these materials as trapped field magnets. However, bulk superconducting rings are very susceptible to thermomagnetic instabilities during the PFM process, and thus, to date, the reported trapped fields in ring bulks magnetized by PFM are less than 0.35 T at the centre of single rings.In this work, we demonstrate that the trapped field in a superconducting ring bulk can be enhanced significantly by optimizing the waveform of the magnetizing pulse used in the PFM method. This optimization can be achieved easily by using an Insulated Gate Bipolar Transistor as a fast-switching device with a controllable switching frequency in the pulse-generating electric circuit. Our findings represent a key step forward in utilizing bulk, singlegrain superconducting rings magnetized by PFM in portable magnet systems.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Waveform Control Pulsed Field Magnetization of RE-Ba-Cu-O Bulk Superconducting Rings

Tsui¹,

Moseley

Dennis³

et al. 2022

IEEE Trans. Appl. Supercond.

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“…Numerous studies of bulk superconductors and stacks of HTS-tapes [1,15,18,24,[26][27][28][29][30][31][32][33][34][35][36][37] are dedicated to the socalled flux jumps (or 'giant field leaps' as first introduced in [27]). These jumps occur at certain critical (or activation) fields and result in a rapid invasion of the magnetic flux into the superconducting samples.…”

Section: Introductionmentioning

confidence: 99%

“…They can make the PFM procedure unreliable (especially at low temperatures or high ramprates of the magnetic field [1]), causing the sample to heat up, reducing the local critical current density, and inducing additional mechanical stress [15,33,38]. However, the flux jumps can also be exploited to improve the field-trapping properties [24,28,29,35] as they can substantially reduce the minimum applied field needed to obtain a desirable TF (resulting in a non-Bean-like flux penetration). The ambient (working) temperature can greatly influence these jumps: their magnitude, the critical field at which they occur, and the resulting TF.…”

Section: Introductionmentioning

confidence: 99%

Thermal behavior of ﬂux jumps and inﬂuence of pulse-shape on the trapped ﬁeld during pulsed magnetization of a high-temperature superconductor

Moroz¹,

Kashurnikov²,

Rudnev³

et al. 2021

J. Phys.: Condens. Matter

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The impact of temperature on the pulsed magnetization of a high-temperature superconductor (HTS) has been numerically studied. The resulting trapped field (TF) and its distribution over the HTS have been calculated for samples with random and periodic pinning (a regular triangular lattice). The increasing ambient temperature (within the considered values) has been shown to improve the field-trapping efficiency and lead to the possibility of pumping more flux into the sample with each consecutive pulse (contrary to the low-temperature case). Various pulse shapes produced different results at high temperatures. Trapezoidal pulses showed the highest efficiency owing to the constant-field segments during which the vortices continued to enter the sample. The critical (activation) field of flux jumps has been shown to decrease with the rising temperature. At the highest considered temperature (30 K), the flux jumps occurred during the TF relaxation. To the best of our knowledge, such calculations have been done for the first time.

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“…Recently, we have applied the the waveform control pulse magnetization (WCPM) method [18] to modify the waveform of the magnetizing pulses to increase trapped fields in a Gd-Ba-Cu-O bulk superconducting ring using single-pulse PFM [19]. We found that the trapped field was enhanced significantly when an optimum magnetizing pulse was used and a maximum trapped field of 0.76 T at 73 K was achieved.…”

Section: Introductionmentioning

confidence: 99%

Trapped Fields >1 T in a Bulk Superconducting Ring by Pulsed Field Magnetization

Tsui¹,

Moseley

Dennis³

et al. 2022

IEEE Trans. Appl. Supercond.

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One potential application of magnetized RE-Ba-Cu-O (where RE = rare earth or Y) bulk superconductors is as a highfield alternative to conventional permanent magnets in desktop NMR and MRI systems. Pulsed field magnetization (PFM) is one of the most promising practical methods of magnetizing such bulks. However, the trapped fields obtained by PFM are much lower than those obtained using quasi-static methods like field-cooling magnetization (FCM) due to heating during PFM. Furthermore, bulk superconducting rings have proved more difficult to magnetize via PFM than discs. The reported trapped fields in single bulk superconducting rings magnetized by PFM are less than 0.35 T at the centre of the bore due to thermomagnetic instabilities. In this work, systematic PFM measurements on a bulk Gd-Ba-Cu-O ring were carried out and a trapped field of 1.3 T at 55 K was achieved using a multi-pulse, stepwise cooling (MPSC) method. In the MPSC method, a sequence of pulsed fields is used to magnetize the ring bulk. The pulsed field is increased in small increments and the sample temperature is decreased sequentially. Consequently, as some field is already trapped after the first pulse, the motion of the flux for subsequent pulses will be reduced, leading to less heat generated in the bulk sample. This greatly improves the thermomagnetic stability of the PFM process, enabling larger trapped fields.

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Waveform Control Pulse Magnetization for HTS Bulk With Flux Jump

Cited by 18 publications

References 11 publications

Waveform Control Pulsed Field Magnetization of RE-Ba-Cu-O Bulk Superconducting Rings

Waveform Control Pulsed Field Magnetization of RE-Ba-Cu-O Bulk Superconducting Rings

Thermal behavior of ﬂux jumps and inﬂuence of pulse-shape on the trapped ﬁeld during pulsed magnetization of a high-temperature superconductor

Trapped Fields >1 T in a Bulk Superconducting Ring by Pulsed Field Magnetization

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