Patent ID: 7535220

Claim:
A beam measuring device comprising: a magnetic shielding part, shielding an outer magnetic field; and a plurality of magnetic field sensors, arranged in a shielding space which is formed by the magnetic shielding part, the magnetic field sensors measuring a magnetic field which a beam current to be measured generates; wherein the magnetic field sensor includes a plurality of magnetic field collection mechanisms which collect magnetic fields which the beam current to be measured generates; wherein the magnetic field collection mechanisms are arranged such that a superconductive surface shielding current is concentrated on a predetermined region by interrupting the superconductive surface shielding current except for a predetermined region on a superconductive surface of the magnetic field collection mechanisms; wherein the magnetic field collection mechanism is a pipe-shaped structural body which has at least a surface thereof formed of a superconductive body and includes a bridge portion which has only a portion thereof constituted of a high-temperature superconductive body on an outer peripheral portion; and wherein the magnetic field collection mechanism concentrates a superconductive surface shielding current which the beam current generates in the vicinity of a plurality of magnetic field sensors.