This invention provides a circular accelerator for revolving charged particles along a revolution path and accelerating the charged particles to a predefined energy, such that the charged particles, which exceeds a stable region formed by multipole electromagnets (41, 42), are biased from the revolution path to an irradiating path to be irradiated the circular accelerator includes a miltipole electromagnetic excitation control section (9) for controlling exercitation of the multipole electromagnets the miltipole electromagnetic excitation control section (9) sets the exercitation of the multiple electromagnets (41, 42) so as to bias a part of the charged particles away from the irradiating path to an abandoned path for abandoning ineffective charged particles, and thereafter set the exercitation of the multipole electromagnets (41, 42) so as to bias the charged particles revolving along the revolution path to the irradiating path.本發明係提供一種圓形加速器,使荷電粒子沿著繞轉軌道繞轉並加速至預定的能量,且使超過藉由多極電磁鐵(41、42)所形成之穩定區域的荷電粒子的軌道從繞轉軌道偏移至出射軌道而射出,該圓形加速器係具備控制多極電磁鐵之激磁的多極電磁鐵激磁控制部(9);多極電磁鐵激磁控制部(9)係在設定多極電磁鐵(41、42)的激磁以使荷電粒子的一部分偏移至出射軌道以外的廢棄軌道而廢棄無用荷電粒子之後,設定多極電磁鐵(41、42)的激磁以使繞轉繞轉軌道之荷電粒子的軌道偏移至出射軌道而使荷電粒子射出。1‧‧‧初段加速器2‧‧‧高頻加速空洞3‧‧‧偏向電磁鐵5‧‧‧四極電磁鐵7‧‧‧出射用電極9‧‧‧多極電磁鐵激勵控制部38‧‧‧入射裝置39‧‧‧出射端口40‧‧‧電磁鐵群41‧‧‧第1六極電磁鐵(六極電磁鐵)42‧‧‧第2六極電磁鐵(六極電磁鐵)43‧‧‧衰減器50‧‧‧照射裝置60‧‧‧患者70‧‧‧出射裝置100‧‧‧同步加速器本體(圓形加速器)
