Magnetic evaluation of HTS magnetic shielding cylinders using an HTS dc-SQUID

For practical applications, an ideal magnetic shielded vessel can be realiz ed by making use of a high-critical temperature superconductor (HTS). Gener ally, the value of the maximum shielded magnetic flux density B-s is used t o evaluate the magnetic shielding effect of the HTS vessel. Little is known , however, of the characteristics and evaluation procedures used to determi ne the behavior of the magnetic flux density B-in within the shielded vesse l when exposed to an external magnetic flux density B-ex of less than the v alue of B-s. In order to evaluate the behavior of the magnetic field within the Bi-Pb-Sr-Ca-Cu-O cylinder to an applied B-ex, the temporal change of B -in, and the magnetic noise power spectrum (NPS) of B-in are measured by an HTS dc-SQUID magnetometer and spectrum analyzer. The present paper examine s the optimum shielding conditions for constructing an ideal magnetic shiel ding vessel.