Particle-beam control electromagnet and irradiation treatment apparatus equipped therewith
A particle-beam control electromagnet capable of shortening a transportation path of a particle beam and an irradiation treatment apparatus which contributes to miniaturization and weight reduction of the rotating gantry supporting this control electromagnet are provided. The electromagnet includes a first superconducting coil group, a second superconducting coil group, and a vacuum vessel. The first superconducting coil group forms at least one of a bending magnetic field and a focus/defocus magnetic field. The second superconducting coil group is placed around the trajectory of the particle beam at the end of the first superconducting coil group and forms correction magnetic fields for correcting the trajectory of the particle beam. The vacuum vessel hermetically houses the first superconducting coil group, the second superconducting coil group, and a cooling medium, and insulates from the outside air.
1. A particle-beam control electromagnet comprising:
a first superconducting coil group configured to form a bending magnetic field and a focus/defocus magnetic field, the bending magnetic field is for bending a traveling direction of a particle beam passing through inside of a vacuum duct and the focus/defocus magnetic field is for controlling an outer diameter of the particle beam;
a second superconducting coil group configured to be placed around a trajectory of the particle beam at an end portion of the first superconducting coil group and form a correction magnetic field for correcting the trajectory of the particle beam; and
a vacuum vessel configured to hermetically house the first superconducting coil group, the second superconducting coil group and a cooling medium to insulate from outside air,
wherein the first superconducting coil group includes a first focus/defocus coil group and a second focus/defocus coil group arranged side by side along the trajectory of the particle beam, each focus/defocus coil group forming the focus/defocus magnetic field and including an even number of excitation coils placed axially symmetrically with respect to the trajectory of the particle beam, current flow in the excitation coils of the second focus/defocus coil group being opposite to current flow in the excitation coils of the first focus/defocus coil group.
2. The particle-beam control electromagnet according to claim 1 , wherein the first superconducting coil group is configured by a bending coil and the focus/defocus coil groups are arranged coaxially stacked, the bending coil is for forming the bending magnetic field.
3. The particle-beam control electromagnet according to claim 2 ,
wherein the focus/defocus coil groups and the second superconducting coil group are configured to form a first layer which faces the vacuum duct; and
the bending coil is configured to form a second layer stacked on the first layer.
4. The particle-beam control electromagnet according to claim 1 , wherein the second superconducting coil group includes:
a first correction coil configured to form a first correction magnetic field in a direction orthogonal to a traveling direction of the particle beam; and
a second correction coil configured to form a second correction magnetic field, which is orthogonal to the traveling direction of the particle beam and a direction of the first correction magnetic field.
5. The particle-beam control electromagnet according to claim 4 , wherein the first correction coil and the second correction coil are arranged to be coaxially stacked.
6. An irradiation treatment apparatus comprising:
the particle-beam control electromagnet according to claim 1 ;
a rotating gantry configured to support the control electromagnet, rotate about a central axis, and irradiate the particle beam in a direction orthogonal to the central axis; and
a bed configured to perform moving and positioning of a patient placed thereon with respect to the particle beam to be irradiated.
7. The irradiation treatment apparatus according to claim 6 , wherein the particle-beam control electromagnets are placed to be the trajectory of the particle beam orthogonal to the central axis.