A structure configuring a ridge filter has line symmetry about a line vertical to a depth direction passing the center of the structure. A small structure obtained in such a way that the structure is divided by this line has a bilaterally asymmetric shape about a center line in an iterative direction, and has a point symmetric shape about an intersection between the center line in the iterative direction and the center line in the depth direction. Thicknesses in the iterative direction of an uppermost stream surface and a lowermost stream surface in the depth direction are equal to each other. The structure is configured so that a thick portion in the iterative direction of the uppermost stream surface and the lowermost stream surface is not present in the depth direction.

Embodiments disclose an energy degrader for attenuating the energy of a charged particle beam, comprising a first energy attenuation member presenting a beam entry face having the shape of a part of a first helical surface, a second energy attenuation member presenting a beam exit face having the shape of a part of a second helical surface, the beam exit face being positioned downstream of said beam entry face with respect to the beam direction, and a drive assembly for rotating the first and/or the second energy attenuation members about respectively a first and/or a second rotation axis while crossed by the particle beam. The first and second helical surfaces are continuous surfaces and have the same handedness, to enable a more compact degrader with a smaller moment of inertia.

In an example, a synchrocyclotron includes a particle source to provide pulses of ionized plasma to a cavity; a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator. The particle source is configured to control pulse widths of the ionized plasma in order to control an intensity of the beam of particles. This example synchrocyclotron may include one or more of the following features, either alone or in combination.

In an example, a synchrocyclotron includes a particle source to provide pulses of ionized plasma to a cavity; a voltage source to provide a radio frequency (RF) voltage to the cavity to accelerate particles from the plasma column outwardly; and an extraction channel to receive a beam of particles from the cavity for output from the particle accelerator. The particle source is configured to control pulse widths of the ionized plasma in order to control an intensity of the beam of particles. This example synchrocyclotron may include one or more of the following features, either alone or in combination.

A high gradient linear accelerating structure can propagate high frequency waves at a negative harmonic to accelerate low-energy ions. The linear accelerating structure can provide a gradient of 50 MV/m for particles at a β of between 0.3 and 0.4. The high gradient structure can be a part of a linear accelerator configured to provide an energy range from an ion source to 450 MeV/u for .sup.12C.sup.6+ and 250 MeV for protons. The linear accelerator can include one or more of the following sections: a radiofrequency quadrupole (RFQ) accelerator operating at the sub-harmonic of the S-band frequency, a high gradient structure for the energy range from ˜45 MeV/u to ˜450 MeV/u.

A high gradient linear accelerating structure can propagate high frequency waves at a negative harmonic to accelerate low-energy ions. The linear accelerating structure can provide a gradient of 50 MV/m for particles at a β of between 0.3 and 0.4. The high gradient structure can be a part of a linear accelerator configured to provide an energy range from an ion source to 450 MeV/u for .sup.12C.sup.6+ and 250 MeV for protons. The linear accelerator can include one or more of the following sections: a radiofrequency quadrupole (RFQ) accelerator operating at the sub-harmonic of the S-band frequency, a high gradient structure for the energy range from ˜45 MeV/u to ˜450 MeV/u.

A particle accelerator comprises a waveguide configured to accelerate a beam of electrons along an acceleration path. A diversion channel is configured to convey a beam of electrons along a diversion path. A first magnet arrangement is configured to, at a first location, direct electrons from the acceleration path to the diversion path. A second magnet arrangement is configured to, at a second location, direct electrons from the diversion path to the acceleration path.

An exciter for a high frequency resonator. The exciter may include an exciter coil inner portion, extending along an exciter axis, an exciter coil loop, disposed at a distal end of the exciter coil inner portion. The exciter may also include a drive mechanism, including at least a rotation component to rotate the exciter coil loop around the exciter axis.

An exciter for a high frequency resonator. The exciter may include an exciter coil inner portion, extending along an exciter axis, an exciter coil loop, disposed at a distal end of the exciter coil inner portion. The exciter may also include a drive mechanism, including at least a rotation component to rotate the exciter coil loop around the exciter axis.

A proton beam imaging system includes: a proton beam generator to generate a proton beam; a proton beam modulator through which the proton beam passes positioned between the proton beam generator and an image target; and a proton beam detector positioned to detect the proton beam existing the image target; wherein the proton beam modulator comprises: a rotating wheel having an axis of rotation positioned so that the proton beam passes through the axis of rotation and the axis of rotation is perpendicular to the proton beam; a first modulating portion comprising a first material portion and a second material portion through which a proton beam passes; and a second modulating portion comprising a third material portion and a fourth material portion through with the proton beam passes; wherein the first and second wedges are positioned opposite each other on the rotating wheel.