• K. Mizushima, T. Furukawa, Y. Iwata, K. Noda, S. Sato, T. Shirai
  NIRS, Chiba-shi
• T. Fujisawa, H. Uchiyama
  AEC, Chiba

A 3D scanning method gated with patient's respiration has been developed for the HIMAC new treatment facility. In the scanning irradiation, the RF-KO slow-extraction method has been used, because of the quick response to beam on/off from the synchrotron. However, a small amount of beam remained just inside the separatrix is extracted just before turning on the transverse RF field, which brings the extra dose. We proposed to apply another transverse RF-frequency component matched with the betatron frequency of the particles in the vicinity of the stopband, in addition to the original transverse RF field for the RF-KO slow-extraction. Using the proposed method, the particles just inside the separatrix, which cause the extra dose, can be selectively extracted during the irradiation; as a result, the extra dose can also be reduced. The validity of this approach has been verified by the simulation and the measurement with the non-distractive 2D beam profile monitor. We will report the result of this approach.