Patent ID: 6218923
Filing Date: 2001-04-17
Classification: G01R

Abstract:
A magnet comprising:a) a longitudinally-extending axis;b) at least one main coil coaxially aligned about said longitudinally-extending axis and carrying an electric current in a first direction;c) at least one shielding coil coaxially aligned about said axis, disposed radially outward from said at least one main coil, and carrying an electric current in an opposite direction to said first direction; andd) a magnetizable member which is not carrying an electric current, which is disposed radially outward from said at least one main coil, and which is disposed radially inward from said at least one shielding coil;said magnetizable member being ring shaped and positioned intermediate and coaxial with said at least one main coil and said at least one shielding coil; andsaid magnetizable member extending longitudinally along said axis to longitudinally overlap said at least one main magnet coil and said at least one shielding coil.