Patent ID: 8373145

Claim:
A particle beam irradiation apparatus for cancer therapy of a tumor of a patient, said apparatus controlling an operational magnetic field, wherein the operational magnetic field controls direction of charged particles, said apparatus comprising: a synchrotron comprising turning magnets, a magnetic field sensor, a gap through which the charged particles pass during use, and at least one correction coil, said magnetic field sensor placed proximate said gap in said synchrotron, wherein, said turning magnets comprise: windings operating at a first power level to generate a first magnetic field about said gap; and said at least one correction coil operating at a second power level, said second power level less than about five percent of said first power level, to generate a correction magnetic field about said gap during use, wherein the first magnetic field and the correction magnetic field combine to yield the operational magnetic field during use, wherein said synchrotron adjusts to a target magnetic field strength via monitoring the operational magnetic field to determine said second power level, wherein as a result of lower power consumption said second power level allows for more accurate and/or precise control of the operational magnetic field.