The applicant of the present patent application has proposed a magnetic field generator of this kind in JP-A 2001-70280. The magnetic field generator includes a first magnetic circuit which is a closed circuit provided by magnets, and a second magnetic circuit provided by attaching magnets which are magnetized in a direction perpendicular to the direction of magnetic flux of the first magnetic circuit, to the magnets that provide the first magnetic circuit. The magnetic field generator is characterized by that the two magnetic fluxes, one generated by the first magnetic circuit and the other generated by the second magnetic circuit, overlap each other.
In this magnetic field generator, due to a fact that relative permeability of permanent magnets is close to 1, it is sometimes impossible to sufficiently introduce the magnetic flux generated by the second magnetic circuit into the magnetic field generation space, leading to decreased efficiency of the magnetic circuit and reduced intensity of the magnetic field generated in the magnetic field generation space.
It is therefore a primary object of the present invention to provide a magnetic field generator and an MRI apparatus using the generator, capable of generating a greater magnetic field intensity.