A septum magnet includes a yoke (1) that is arc-shaped, that has a gap portion (1s) opening at the outer circumference side thereof and extending in a circumferential direction thereof, and that can be separated at the approximately center portion thereof in the axis direction a septum coil (3) that is provided inside the gap portion (1s) but at the outer side thereof in the radial direction and in which an electric current flows in one direction in the circumferential direction a return coil (4) that is provided in such a way as to be at the inner side of the gap portion (1s) in the radial direction and to face the septum coil (3) with a predetermined distance, and in which an electric current flows in opposite direction to that of the electric current in the septum coil (3) and a vacuum duct (2) that is inserted between the septum coil (3) and the return coil (4). The septum coil (3) is formed in such a way as to be able to be separated into a first portion (3u) and a second portion (3d) in response to separation of the yoke (1) and in a space between the septum coil (3) and the vacuum duct (2), there is provided an auxiliary coil (5), in two portions of which, corresponding to the first portion (3u) and the second portion (3d) of the septum coil (3), electric currents flow in opposite direction to each other in the circumferential direction.本發明之中隔電磁石,係具備:軛鐵(1),形成弧狀,且具有開口於外周側並延伸於圓周方向的空隙部(1s),以能夠在軸向之大致中央部進行分割的方式所構成;中隔線圈(3),設置於空隙部(1s)內之徑向的外側,並供電流朝向圓周方向之一方向流動;返回線圈(4),以與中隔線圈(3)隔出預定之間隔而對向的方式設置在空隙部(1s)內之徑向的內側,並供與中隔線圈(3)的電流呈逆向之電流流動;以及真空導管(2),設置在中隔線圈(3)與返回線圈(4)之間,中隔線圈(3)係形成為:對應軛鐵(1)之分割而能夠分離成第1部分(3u)和第2部分(3d),並且在中隔線圈(3)與真空導管(2)之間設置有輔助線圈(5),該輔助線圈(5)係在對應於中隔線圈(3)之第1部分(3u)和第2部分(3d)的部分(5u、5d)流動在圓周方向中彼此逆向之電流。1‧‧‧軛鐵1d‧‧‧下軛鐵1s‧‧‧空隙部1u‧‧‧上軛鐵2‧‧‧真空導管3‧‧‧中隔線圈3d‧‧‧下中隔線圈(第2部分)3u‧‧‧上中隔線圈(第1部分)4‧‧‧返回線圈4d‧‧‧下返回線圈4u‧‧‧上返回線圈5‧‧‧輔助線圈5d‧‧‧下輔助線圈(對應第1部分之部分)5u‧‧‧上輔助線圈(對應第1部分之部分)6‧‧‧磁性屏蔽10‧‧‧中隔電磁石11‧‧‧導管(環繞軌道路徑)c‧‧‧圓周方向h‧‧‧軸向Pm‧‧‧中平面r‧‧‧徑向
