Evaluation of the magnetic field within a BPSCCO cylinder superimposed by multi-layered soft-iron cylinders by use of an HTS DC-SQUID

The evaluation of the maximum shielded magnetic flux density B_s of a high-critical temperature superconducting (HTS) cylinder acting as a magnetic shielding vessel, is required to improve the value of B_s for practical use. The authors have improved the value of B_s by the superposition of multi-layered soft-iron cylinders over a Bi-Pb-Sr-Ca-Cu-O cylinder which is termed the superimposed cylinder. Little is known, however, of the characteristics and evaluation procedures for the magnetic flux density B_ia within the innermost of the superimposed cylinders when the value of the external magnetic flux density B_ex is less than that of B_s. The present research has evaluated the shielding effect for the superimposed cylinder with the use of an HTS DC-SQUID magnetometer and spectrum analyzer. The present paper examines the magnetic step response of B_in to the applied B_ex, the characteristics of B_in when exposed to a B_ex having a value less than that of B_s, and the magnetic noise power spectra within the superimposed cylinder. In addition, a discussion is conducted on the relationship between the number of layers of the multi-layered soft-iron cylinder and the value of B_in