Method and apparatus for adjusting magnetic field homogeneity of an actively shielded cylindrical superconducting magnet

摘要

A method for adjusting the magnetic field homogeneity of an actively-shielded cylindrical superconducting magnet, comprising an inner magnet assembly (21) itself comprising end coils (10) and inner coils (14) aligned on a common axis (A-A) between the end coils, said inner coils and said end coils defining a bore (18); and one or more shield coils (12) of greater diameter than the end coils (10) and inner coils (14). The method comprises the steps of: applying electric current to the shield coils, the inner coils and the end coils to generate a magnetic field within an imaging region (20) defined within the bore (18); measuring a homogeneity of the magnetic field within the imaging region (20) and adjusting a position of at least one of the shield coils (12) with respect to the inner magnet assembly (21). Alternatively the shield coils can be removed or replaced in order to change constructional details such as the number of coil turns or diameter, or in the case of coil defects.