Influence of Jc(B) on the full penetration current of superconducting tube

Abstract

International audienceIt is well known that the critical current density Jc of a superconducting material depends on the magnetic field B. If magnetic independent Jc is chosen for analytical calculation of current distribution, the critical current Ic corresponds to full penetration current Ip. Ic is a measured current with 1 lV/cm criterion and Ip is a calculated current. The aim of this paper is to calculate the influence of the Jc(B) variation on Ip of a superconducting tube. To calculate Ip, which is depending on the material itself, a linear function Jc(B) is sufficient to obtain realistic values by analytic way. We need to have a linear Jc(B) law that is close to the measured Jc(B) characteristics presented in this paper. The linear Jc(B) law chosen was used for the calculation of the distribution of both magnetic field B(r, t) and the current density J(r, t). These distributions allow the analytical calculation of Ip. The calculated results of magnetic field distribution and full penetration current with Bean model and linear model are compared. We also present the variation of critical current with the characteristic parameters of the material. The present results, allow to understand the relationship between the full penetration current variation of a sample and the variation of the Jc(B) characteristics

Self Field Effect Compensation in an HTS Tube

“…The analytical calculation of the magnetic flux density and current density distributions in the superconducting material is difficult [3] because (1) with has to be solved. One can simplify calculation of these distributions with three hypotheses.…”

“…3) The critical current and the full penetration current [3] are equal. With these hypotheses one can calculate as follows: with and .…”

“…For this reason it is important to know well the dependence of a tube. Measurements of can be achieved by electrical transport (direct) [3] or magnetic (indirect) [4] methods. In this paper, the electrical method used to define the of a superconducting tube is studied.…”

“…In this paper, the electrical method used to define the of a superconducting tube is studied. Electrical transport measurements are achieved by the standard four-probe technique, which involves injecting a dc current in the superconducting tube and measuring the voltage drop [3]. Throughout this paper, the extremity effects are neglected because the voltage taps are sufficiently distant from the tube extremities.…”

“…To theoretically calculate, for example, ac losses or magnetization, we can use Bean's critical state model that defines the relation between electric field and current density as or . To obtain the experimental curve of , the tube was fed with direct current and submitted to an external magnetic flux density parallel to the axis [3]. The sample voltage drop versus is measured for different external magnetic flux densities .…”