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/sub s/ of a high-critical temperature superconducting (HTS) cylinder acting as a magnetic shielding vessel, is required to improve the value of B/sub s/ for practical use. The authors have improved the value of B/sub 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/sub ia/ within the innermost of the superimposed cylinders when the value of the external magnetic flux density B/sub ex/ is less than that of B/sub 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/sub in/ to the applied B/sub ex/, the characteristics of B/sub in/ when exposed to a B/sub ex/ having a value less than that of B/sub 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/sub in/.