Improved pulsed field magnetisation in MgB<sub>2</sub> trapped-field magnets

Moseley, Dominic; Matthews, G. P.; Zhou, Difan; Cientanni, Vito; Tsui, Y. K.; Ainslie, Mark; Speller, Susannah; Durrell, John

doi:10.1088/1361-6668/ac0951

Cited by 11 publications

(19 citation statements)

References 45 publications

(80 reference statements)

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“…Heat was thus less effectively removed nearer the top of the sample during the magnetizing process. This could be mitigated in the future by redesigning the copper sample holder: it was shown recently in [26], for example, that an 'encapsulated head' cooling architecture can significantly improve the PFM of bulk MgB 2 , which are highly susceptible to thermomagnetic instabilities [27].…”

Section: Trapped Field Uniformity Within the Ring Borementioning

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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Section: Trapped Field Uniformity Within the Ring Borementioning

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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“…properties makes MgB 2 an attractive candidate to replace "traditional" LTS materials such as NbTi in applications including MRI machines and magnetic drug targeting devices [2,3].…”

Section: Introductionmentioning

confidence: 99%

“…This method has the advantage of producing sintered specimens showing high inter-grain connectivity. On the other hand, the large density difference between the precursor powders (2.10 g/cm 3 for the powder mixture compared to 2.63 g/cm 3 for MgB 2 ) leads to extremely porous specimens, which in turn reduces the total cross sectional area for supercurrents and also results in poor mechanical properties [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…In addition, MgB 2 does not contain any rare earth or toxic elements and is also much easier and cheaper to process than high temperature superconductors such as the cuprates [1]. This combination of properties makes MgB 2 an attractive candidate to replace 'traditional' LTS materials such as NbTi in applications including MRI machines and magnetic drug targeting devices [2,3].…”

Section: Introductionmentioning

confidence: 99%

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Improving the connectivity of MgB₂ bulk superconductors by a novel liquid phase sintering process

Matthews

Mousavi

Santra

et al. 2022

Supercond. Sci. Technol.

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This work investigates a new processing method developed to improve the connectivity of ex-situ MgB2 bulks at low sintering temperatures. Mg additions (1 − 10 wt.%) were mixed to pre-synthesised MgB2 to make composite powders that were sintered at 900 ﬃC by the Field Assisted Sintering Technique (FAST). Addition of 10 wt.% Mg resulted in a substantial increase in density from 68 to 79% and a dramatic reduction in MgB4from 11 to ∼ 0 wt.%. Pressure and dilatometry data recorded in-situ during the sintering process revealed that Mg additions led to diﬀerent sintering mechanisms depending on the Mg fraction. For large Mg fractions (6 and 10 wt.%) a Mg liquid phase was formed and led to signiﬁcant density improvements, and all pre-existing MgB4 was transformed into MgB2. A small amount of residual Mg remained in the bulks after the sintering process. Connectivity was improved with Mg additions, increasing 4 fold in the 10 wt.% Mg-MgB2 sample compared to unmodiﬁed MgB2. Jc values at low ﬁeld were also signiﬁcantly improved by Mg additions, in particular the 6 and 10 wt.% Mg-MgB2 specimens showed Jc(20 K, 0 T) values 4 − 5 times higher than for unmodiﬁed MgB2.

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“…The Bulk Superconductivity Group at the University of Cambridge has developed a new PFM system based on a system reported previously for magnetizing bulk (RE)BCO single grains of disc-shaped geometry [8,16]. The cryocooler of the original system has been upgraded in the present study to a Sunpower CryoTel GT cryocooler.…”

Section: Introductionmentioning

confidence: 99%

Portable, desktop high-field magnet systems using bulk, single-grain RE–Ba–Cu–O high-temperature superconductors

Tsui

Moseley

Beck

et al. 2022

Supercond. Sci. Technol.

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Bulk high-temperature superconducting materials can trap magnetic fields up to an order of magnitude larger than conventional permanent magnets. Recent advances in pulsed field magnetization (PFM) techniques now provide a fast and cost-effective method to magnetize bulk superconductors to fields of up to 5 T. We have developed a portable, desktop bulk high-temperature superconducting magnet system by combining advanced PFM techniques with state-of-the-art cryocooler technology and single-grain, RE-Ba-Cu-O [(RE)BCO, where RE is a rare-earth element or yttrium] bulk superconducting materials. The base temperature of the system is 41 K and it takes about one hour for the system to cool down to 50 K from room temperature. A capacitor bank, combined with easily-interchangeable, solenoid- or split-type copper magnetizing coils and an insulated bipolar gate transistor acting as a high-speed switch, allows magnetic pulses to be generated with different pulse profiles. The system is capable of trapping magnetic fields of up to ~3 T. In this work, we report the results of the magnetization of a range of single-grain Y-Ba-Cu-O (YBCO), Eu-Ba-Cu-O (EuBCO) and Gd-Ba-Cu-O (GdBCO), bulk superconducting discs using this system. A higher trapped field was recorded using a split coil incorporating iron yokes at temperatures of 65 K and above, whereas at lower temperatures, a higher trapped field was obtained using the solenoid coil. The GdBCO sample achieved the highest trapped field for both single-pulse (SP) and two-stage-multi-pulse (TSMP) methods using the solenoid coil. Maximum trapped fields of 2.26 T at 55 K and 2.85 T at 49 K were recorded at the centre of the top surface of the GdBCO sample for the SP and TSMP methods, respectively. The PFM process is substantially an adiabatic process so, therefore, the thermal contact between the sample and sample holder is of critical importance for cooling the bulk sample during application of the pulse. The design of the sample holder can be modified easily to enhance the thermal stability of the sample in order to achieve a higher trapped field.

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Improved pulsed field magnetisation in MgB₂ trapped-field magnets

Cited by 11 publications

References 45 publications

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

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

Improving the connectivity of MgB₂ bulk superconductors by a novel liquid phase sintering process

Portable, desktop high-field magnet systems using bulk, single-grain RE–Ba–Cu–O high-temperature superconductors

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Improved pulsed field magnetisation in MgB2 trapped-field magnets

Cited by 11 publications

References 45 publications

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

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

Improving the connectivity of MgB2 bulk superconductors by a novel liquid phase sintering process

Portable, desktop high-field magnet systems using bulk, single-grain RE–Ba–Cu–O high-temperature superconductors

Contact Info

Product

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Improved pulsed field magnetisation in MgB₂ trapped-field magnets

Improving the connectivity of MgB₂ bulk superconductors by a novel liquid phase sintering process