Particle beam treatment system and beam position correcting method thereof

A particle beam treatment system comprising:

• an accelerator system that accelerates a charged particle beam;
• and
• a beam transport system that transports a high-energy beam emitted from an accelerator to an irradiation location,
• wherein the beam transport system is provided with two steering electromagnets and two beam position monitors corresponding to the steering electromagnets,
• wherein the first beam position monitor is disposed in the front of the second steering electromagnet and supplies an excitation current for correcting a beam position, which periodically varies, to the first steering electromagnet, and
• wherein the second beam position monitor is disposed in the back of the second steering electromagnet and supplies an excitation current for correcting a beam position, which periodically varies, to the second steering electromagnet.

A beam position correcting method of a particle beam treatment system which includes an accelerator system that accelerates a charged particle beam and a beam transport system that transports a high-energy beam emitted from an accelerator to an irradiation location and in which the beam transport system is provided with at least one steering electromagnet and at least one beam position monitor corresponding to the at least one steering electromagnet, comprising:

• detecting a periodic variation of a beam position by applying a beam in a state where the at least one beam position monitor is detachably disposed at an irradiation location in test irradiation;
• supplying a value of an excitation current to the at least one steering electromagnet in synchronization with the periodic position variation so as to cancel the periodic variation;
• storing a value of the periodic excitation current;
• and
• supplying the stored value of the periodic excitation current to the at least one steering electromagnet in a state where the at least one beam position monitor is detached from the irradiation location in actual irradiation.

A beam position correcting method of a particle beam treatment system which includes an accelerator system that accelerates a charged particle beam and a beam transport system that transports a high-energy beam emitted from an accelerator to an irradiation location and in which the beam transport system is provided with two steering electromagnets and two beam position monitors corresponding to the two steering electromagnets,

• wherein in the test irradiation, current pattern data of the upstream steering electromagnet in which a beam position does not temporally vary is stored by the use of the upstream beam position monitor, which is disposed between the upstream steering electromagnet and the downstream steering electromagnet and in the vicinity of the downstream steering electromagnet, a current applied to the upstream steering electromagnet is adjusted in the stored current pattern, the beam position is observed by the use of the beam position monitor disposed downstream of the downstream steering electromagnet, the current flowing in the downstream steering electromagnet is made to vary, and current pattern data of the downstream steering electromagnet in which the beam position does not temporally vary is stored, and
• wherein in the actual irradiation, the beam position and a beam angle are not made to vary by causing the stored current pattern data to flow in the upstream steering electromagnet and the downstream steering electromagnet in synchronization with a synchrotron periodically operating.

A beam position correcting method of a particle beam treatment system which includes an accelerator system that accelerates a charged particle beam and a beam transport system that transports a high-energy beam emitted from an accelerator to an irradiation location, comprising:

• observing a position variation of a beam periodically accelerated and emitted by a synchrotron by the use of a beam position monitor disposed downstream of a deflection electromagnet in a final stage of the beam transport system;
• calculating a beam trajectory of the beam transport system on the basis of the observation result;
• disposing a steering electromagnet at a position s at which a beam position X0(s) at the position s when there is no disturbance and a beam position X1(s) at the position s when there is disturbance are equal to each other, that is, the position at which X0(s)=X1(s) is satisfied, acquiring and storing a current pattern in which a beam position does not vary by the use of the beam position monitor by causing a current to flow in the steering electromagnet in test irradiation;
• and
• causing the beam position and a beam angle not to vary by causing a current corresponding to the current pattern to flow in actual irradiation.

A beam position correcting method of a particle beam treatment system which includes an accelerator system that accelerates a charged particle beam and a beam transport system that transports a high-energy beam emitted from an accelerator to an irradiation location and in which the beam transport system is provided with two steering electromagnets and two beam position monitors disposed in the back of the two steering electromagnets, comprising:

• detecting a detection signal X1(t) of a beam position at each time t by the use of the first beam position monitor;
• detecting a detection signal X2(t) of the beam position at each time t by the use of the second beam position monitor;
• calculating a kick angle at each time at which X1 and X2 are able to be set to 0;
• creating current patterns I1(t) and I2(t) corresponding to the calculated kick angle;
• outputting the current patterns as excitation currents of the two steering electromagnets, respectively;
• and
• correcting the beam position so as to be finally located on a beam axis.