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 sh ielding 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-la yered 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-in within the in nermost of the superimposed cylinders H hen the value of the external magne tic flux density B-ex is less than that of B-s. The present research has ev aluated the shielding effect for the superimposed cylinder with the use of an HTS dc-SQUID magnetometer and spectrum analyzer. The present paper exami nes the magnetic step response of B-in to the applied B-ex. the characteris tics of B-in when exposed to a B-ex having a value less than that of B-s, a nd the magnetic noise power spectra within the superimposed cylinder. In ad dition, 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.