Magnetic Shielding Characteristics of Second Generation High Temperature Superconductors at Variable Temperatures Obtained by Cryogenic Helium Gas Circulation

Abstract

Magnetic shielding characteristics of 40 mm wide second generation high temperature superconducting (2GHTS) materials were studied at variable temperatures. Shielding characteristics were measured in DC and variable frequency AC magnetic fields at a range of magnitudes up to 60 mT. Magnetic shields fabricated in the form of short cylinders were studied with magnetic field perpendicular to their axis. Shielding properties of single and double layer shields were compared at various temperatures between 50 and 80 K. Shielding factor up to 98% was achieved. The benefit of lower temperatures is particularly visible at higher magnetic fields. Trends of shielding characteristics modeled as a function of external magnetic field strength with finite element models using COMSOL match with those of the experimental observations.Index Terms-Comsol model, Hall sensor, Helium gas, magnetic field, magnetic shielding, shielding factor, YBCO tape. 1051-8223

Magnetic Shielding Above 1 T at 20 K With Bulk, Large Grain YBCO Tubes Made by Buffer-Aided Top Seeded Melt Growth

“…In a good approximation, the limit field Blim is mainly determined by the product of the critical current density Jc and a geometrical dimension which, in most cases, is limited by the wall thickness d of the superconducting enclosure [8]. Films deposited on metallic substrates [9,10] or structures made of coated conductors [11][12][13][14] have the advantage of being easily scalable but are not currently appropriate for shielding high fields because of their small thickness. Bulk cylinders made of high temperature superconductors (HTS), on the other hand, have already demonstrated their high-field shielding abilities.…”

A comparative study of triaxial and uniaxial magnetic shields made out of YBCO coated conductors

“…As a result, the field attenuation provided by these currents is smaller than that obtained for a hollow cylinder. Note, that the screening of the transverse field by this type of shield can be improved by using wider coated conductors, like the 40 mm wide conductors used in [33,34]. In order to understand how the stack reacts to a magnetic field applied perpendicular to its axis and rotated in this plane, we consider a single loop of the stack ( figure B1(a)).…”

Shape optimization for superconductors governed by H(curl)-elliptic variational inequalities

“…This example is motivated by the HTS application in the superconducting shielding (cf. [22]). We take κ ≡ 8 • 10 7 , which is a reasonable choice considering that the electric field strength is roughly |E| ≈ 10 −3 due to the weak applied current strength |f |.…”

“…The former depends solely on the properties of the material, the operating temperature, and the magnetic field strength, whereas the latter is also highly affected by the geometry. In the case of an HTS coil for instance, physical experiments [22] show that the enclosed area is still shielded even if the opened ends are directly facing the field lines. On the other hand, if the diameter gets too large, field lines start penetrating the inside.…”