Self Field Effect Compensation in an HTS Tube

It is well known that the critical current density J_c of a superconducting material depends on the magnetic flux density B. There exists an electric method to measure the J_c(B) deduced from the U(I) measurements. The problem with this method is the self field effect because the magnetic flux density is always the sum of the applied magnetic flux density and the self magnetic flux density. This paper presents a special experimental arrangement, compensating fully or partially the self magnetic flux density in an HTS tube. It allows characterizing the true zero magnetic flux density behaviour of the superconducting material. The experimental results of the compensation are discussed. A theoretical analysis based on Bean´s model is presented and gives results close to the experimental ones. The proposed compensation is not perfect but the experiments and the theoretical analysis allow validation of the compensation principle.