Trapped magnetic-field properties of prototype for Gd-Ba-Cu-O/MgB₂hybrid-type superconducting bulk magnet

Abstract

We have studied experimentally and numerically the trapped magnetic-field properties of a hybrid-type superconducting bulk magnet, which comprised an inner Gd-Ba-Cu-O (GdBCO) disk-bulk and an outer MgB2 ring-bulk, under field-cooled magnetization (FCM) and pulsed-field magnetization (PFM). The trapped field by FCM at the center of the hybrid bulk was 4.5 T at 20 K, which was 0.2 T higher than that of the inner GdBCO disk-bulk without MgB2 ring-bulk. The experimental results by FCM were quantitatively reproduced by the numerical estimations for a model, which makes it possible to understand the trapped field properties of the hybrid bulk. The total magnetic flux by FCM, which was estimated numerically, was enhanced by about 1.7 times from 0.91 mWb of the single GdBCO bulk to 1.53 mWb of the hybrid bulk. We also succeeded in magnetizing the whole hybrid bulk by applying multi-pulsed-fields. The central trapped field of 1.88 T was not enhanced, but the total magnetic flux, which was obtained experimentally, was evidently increased by 2.5 times (0.25 0.62 mWb) for the hybrid bulk. The obtained results suggest that the hybridization is effective to enhance the total magnetic flux. To confirm the reinforcing effect of the MgB2 ring to the GdBCO disk during the cooling and magnetization processes, we have measured the thermal dilatation, , of the GdBCO, MgB2 and stainless steel. As a result, the thermal dilatation of MgB2 was smaller than that of GdBCO. MgB2 ring-bulk shows no compression effect to resist the hoop stress of the GdBCO disk-bulk during the FCM process. The reinforcing material such as the stainless steel ring must be set outside the GdBCO disk-bulk.

Promising effects of a new hat structure and double metal ring for mechanical reinforcement of a REBaCuO ring-shaped bulk during field-cooled magnetisation at 10 T without fracture

“…where L 300 and L 50 are the lengths of the material at 300 K and 50 K, respectively. The mechanical parameters of the REBaCuO bulk were assumed to be isotropic and homogeneous for simplicity, and typical values of the ab-plane were used, in which the α av value was measured [22].…”

A new MgB2 bulk ring fabrication technique for use in magnetic shielding or bench-top NMR systems

“…The physical size of the samples lie in between the existing machinable FAST samples discussed by Gozzelino et al [2,15] and the larger Namba et al [20] samples formed by infiltration growth. However, they are a similar size to the machined samples of Naito et al [18].…”

Magnetic moment and local magnetic induction of superconducting/ferromagnetic structures subjected to crossed fields: experiments on GdBCO and modelling

“…The ferromagnetic part can be a disk placed on the SC sample [9], a surrounding tube [3,11] or even powder or rods inserted inside holes drilled in the SC pellet [12][13][14]. In addition to the improvement of the magnetic properties [15,16], the metallic character…”

“…Recently, the investigation on the combination of ferromagnetic (FM) and bulk superconducting (SC) materials in macroscopic SC/FM structures was intensively conducted in order to study the influence of the ferromagnet behaviour on the enhancement of the magnetic properties, in particular the trapped flux density [9,10]. The ferromagnetic part can be a disk placed on the SC sample [9], a surrounding tube [3,11] or even powder or rods inserted inside holes drilled in the SC pellet [12][13][14]. In addition to the improvement of the magnetic properties [15,16], the metallic character of the FM part can play a beneficial role as mechanical reinforcement [3] or as a heat conductor [14,17].…”