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.