Patent ID: 7888937

Claim:
A beam current sensor comprising: a super-conductive body, which is a cylindrical body having an inner surface defining an interior and an outer surface, wherein a beam passes through the interior; and a bridge unit to which a SQUID input coil is adjacently arranged is formed on the outer surface; said bridge unit comprising: a first coil unit formed so as to have a spiral shape wound counterclockwise and having a first center; a second coil unit formed so as to have a spiral shape wound clockwise and having a second center; and a connection portion for connecting the first center position of said first coil unit with the second center position of said second coil unit, said beam current sensor comprising: a first soft magnetic body of an approximately rectangular parallelepiped shape arranged on said first coil unit; a second soft magnetic body of an approximately rectangular parallelepiped shape arranged on said second coil unit; and a third soft magnetic body including an approximately U-shape, where one end portion is arranged on said first soft magnetic body side and the other end portion is arranged on said second soft magnetic body side, and which bridges said first soft magnetic body and said second soft magnetic body, wherein said SQUID input coil is arranged between said first soft magnetic body and said one end portion of said third soft magnetic body and between said second soft magnetic body and said other end portion of said third soft magnetic body.