Patent ID: 7361892

Claim:
A method to increase low-energy beam current in an irradiation system with ion beam which is configured that a beam from a beam generation source is caused to pass through a mass analysis device and a beam transformer, then pass through a deflector for scanning which swings the beam reciprocally in a direction perpendicular to the longitudinal direction (that is a scan direction), a beam parallelizing device, an acceleration/deceleration device, and an energy filtering device, and then is incident on an irradiation target, wherein said beam transformer comprises a vertically focusing DC quadrupole electromagnet QD and a longitudinally focusing DC quadrupole electromagnet QF, and said beam transformer transforms a beam having a circular cross-section or an elliptical or oval cross-section so that said beam has an elliptical or oval cross-section that is long in the scan direction in all the region of the beam line after deflection for scanning.