Magnetic shielding properties of high-temperature superconducting tubes subjected to axial fields

Abstract

We have experimentally studied the magnetic shielding properties of a cylindrical shell of BiPbSrCaCuO subjected to low frequency AC axial magnetic fields. The magnetic response has been investigated as a function of the dimensions of the tube, the magnitude of the applied field and the frequency. These results are explained quantitatively by employing the method of Brandt (1998 Phys. Rev. B 58 6506) with a Jc(B) law appropriate for a polycrystalline material. Specifically, we observe that the applied field can sweep into the central region either through the thickness of the shield or through the opening ends, the latter mechanism being suppressed for long tubes. For the first time, we systematically detail the spatial variation of the shielding factor (the ratio of the applied field over the internal magnetic field) along the axis of a high-temperature superconducting tube. The shielding factor is shown to be constant in a region around the centre of the tube, and to decrease as an exponential in the vicinity of the ends. This spatial dependence comes from the competition between two mechanisms of field penetration. The frequency dependence of the shielding factor is also discussed and shown to follow a power law arising from the finite creep exponent n.

Behavior of bulk high-temperature superconductors of finite thickness subjected to crossed magnetic fields: Experiment and model

“…=15,21,25,31͒ has only little effects on the results, as expected from scaling arguments. 39,68 Therefore, even though a finite n value is assumed, the sweep rate is not considered a relevant parameter affecting the results in the E-J-B conditions involved in the present study.…”

Field penetration into hard type-II superconducting tubes: effects of a cap, a non-superconducting joint, and non-uniform superconducting properties

“…The traditional solution of this problem consists in using a piece of ferromagnetic material instead, which can divert the magnetic flux outside the region to be protected [1]. However, hard type-II superconductors, which are strongly diamagnetic, can shield a magnetic field more efficiently than ferromagnetic materials do [2][3][4][5][6], In a recent work [7], we have studied numerically and experimentally the shielding properties of open type-II superconducting tubes that were subjected to a source field applied parallel to the tube axis (parallel geometry). Three factors were considered to evaluate the quality of the shields: (i) the maximum induction that can be strongly attenuated, called B lim , (ii) the spatial variation of the field attenuation, and (iii), the frequency dependence of the field attenuation.…”

“…The results of [7] can be used to design better magnetic shields. For instance, putting a cap at both ends of the tube reduces the penetration from the extremities and thus raises the level of attenuation inside the tube.…”

YBa2Cu3O7−x dispersion in iodine acetone for electrophoretic deposition: Surface charging mechanism in a halogenated organic media

“…Finally, the simple hard wall model described by Bergström [82] was used to approximate the steric stabilization in the YBCO suspension stabilised in I 2 solution, by means: (9) δ represents the thickness of the adsorbed layer, Φ the volume fraction of the adsorbent in the adsorbed layer, is the solvent-adsorbent interaction parameter and V is the molecular volume solvent. This equation is valid in the interpenetrational domain ( 2 ) 2 ( d D ) [82].…”

“…In this sense EPD should be considered as a potential applicable technique, offering a real possibility of industrial scalability and reliability. In fact, EPD has been successfully considered for applications such as magnetic shielding in low frequencies [6][7][8][9][10][11][12]. However, much effort is still necessary to understand and control the complex colloidal behaviour and the surface reactions occurring when YBCO powders are dispersed in a liquid.…”