Laser-driven particle beam irradiation apparatus and method

1. A laser-driven particle beam irradiation apparatus comprising:

a particle beam generator irradiating a target with pulsed laser light to emit a laser-driven particle ray;

a beam converging unit forming a transportation path which guides the emitted laser-driven particle ray to an object to be irradiated and spatially converging the laser-driven particle ray;

an energy selector selecting an energy and an energy width of the laser-driven particle ray;

an irradiation port causing the laser-driven particle ray to scan the object to be irradiated to adjust an irradiation position in the object; and

an irradiation controller controlling operation of the particle beam generator, the beam converging unit, the energy selector, and the irradiation port, wherein

the beam converging unit generates a magnetic field on a trajectory of the laser-driven particle ray and converging the laser-driven particle ray by the magnetic field, the magnetic field forcing divergence components of the laser-driven particle ray that go away from a center of the trajectory back to the center of the trajectory, and

the beam converging unit is provided between the particle beam generator and the energy selector.

2. A laser-driven particle beam irradiation apparatus comprising:

a particle beam generator irradiating a target with pulsed laser light to emit a laser-driven particle ray;

a beam converging unit forming a transportation path which guides the emitted laser-driven particle ray to an object to be irradiated and spatially converging the laser-driven particle ray;

an energy selector selecting an energy and an energy width of the laser-driven particle ray;

an irradiation port causing the laser-driven particle ray to scan the object to be irradiated to adjust an irradiation position in the object;

an irradiation controller controlling operation of the particle beam generator, the beam converging unit, the energy selector, and the irradiation port; and

an energy distribution converging unit forming the transportation path of the laser-driven particle ray and converging an energy distribution of the laser-driven particle ray through the transportation path to provide a peak at a particular energy, wherein

the beam converging unit generates a magnetic field on a trajectory of the laser-driven particle ray and converging the laser-driven particle ray by the magnetic field, the magnetic field forcing divergence components of the laser-driven particle ray that go away from a center of the trajectory back to the center of the trajectory, and

the energy distribution converging unit includes a phase rotation cavity unit forming a transportation path of the laser-driven particle ray and, under application of a high-frequency voltage, generating in the transportation path a high-frequency electric field in which a state in which protons in a bunch are accelerated and a state in which protons in a bunch are decelerated appear to converge the energy distribution of the laser-driven proton ray to a particular energy, and wherein the irradiation controller adjusts the phase of the high-frequency voltage to be applied to the phase rotation cavity unit to adjust the position of the energy peak of the energy distribution of the laser-driven particle ray.

3. The laser-driven particle beam irradiation apparatus according to claim 2 , wherein the phase rotation cavity unit of the energy distribution converging unit includes an outer cavity forming the transportation path of the laser-driven particle ray and a plurality of inner cavities which are spaced in a row in the outer cavity and to which a high-frequency voltage is applied, wherein a high-frequency electric field is formed in a gap between adjacent inner cavities to converge the energy distribution of a proton beam around the energy of protons that enter the gap at a timing of being synchronized with the phase of the high-frequency voltage applied to the inner cavities among the protons in a bunch in the outer cavity.

4. The laser-driven particle beam irradiation apparatus according to claim 3 , wherein the irradiation controller applies a pulse width compressing voltage to the inner cavities of the energy distribution converging unit to generate a high-frequency electric field in the gap between adjacent inner cavities, the pulse width compressing voltage being defined as

V

>

E

0

⁢

β

0

2

⁢

γ

0

2

q

·

1

-

m

2

⁢

c

4

/

E

0

2

1

-

m

2

⁢

c

4

/

E

0

2

+

fL

/

c

wherein f is the frequency of the high-frequency voltage to be applied to the inner cavities, L is the distance from a laser-driven particle ray emission point in the target to the gap between adjacent inner cavities, β 0 and γ 0 are Lorentz factors, E 0 is the total energy of the laser-driven particle ray, c is the speed of light, m is the mass of the laser-driven-particle ray, and q is the charge of the laser-driven particle ray.

5. A laser-driven particle beam irradiation method, comprising:

a particle beam generating step of irradiating a target with pulsed laser light to extract a laser-driven particle ray;

a beam converging step of spatially converging the laser-driven particle ray;

an energy selecting step of selecting an energy and an energy width of the laser-driven particle ray according to a depth of an irradiation position set in an object to be irradiated;

an irradiation step of adjusting the irradiation position of the laser-driven particle ray in the object to be irradiated; and

a pulse width compressing step of reducing the pulse width of the laser-driven particle ray,

wherein, in the beam converging step, a magnetic field forcing divergence components of the laser-driven particle ray that go away from a center of the trajectory of the laser-driven particle ray back to the center of the trajectory is generated on the trajectory and the laser-driven particle ray is converged by the magnetic field.

6. The laser-driven particle beam irradiation method according to claim 5 , wherein, in the pulse width compressing step, a high-frequency electric field induced by a pulse width compressing voltage is generated and the laser-driven particle ray is guided to and passed through the high-frequency electric field to reduce the pulse width of the laser-driven particle ray, the pulse width compressing voltage being defined as

V

>

E

0

⁢

β

0

2

⁢

γ

0

2

q

·

1

-

m

2

⁢

c

4

/

E

0

2

1

-

m

2

⁢

c

4

/

E

0

2

+

fL

/

c

wherein f is the frequency of the high-frequency voltage, L is the distance from a laser-driven particle ray emission point, β 0 and γ 0 are Lorentz factors, E 0 is the total energy of the laser-driven particle ray, c is the speed of light, m is the mass of the laser-driven-particle ray, and q is the charge of the laser-driven particle ray.