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 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 linear accelerator apparatus may include a beamline enclosure that defines a polygonal backbone, and a plurality of acceleration stages, disposed along a length of the beamline enclosure. A given acceleration stage may include a drift tube assembly to conduct an ion beam therethrough, a resonator, coupled to deliver an RF signal to the drift tube assembly, and a quadrupole assembly to shape the ion beam. As such, at a first acceleration stage, a first resonator may be disposed along a first side of the polygonal backbone, and at a second acceleration stage, adjacent to and downstream of the first acceleration stage, a second resonator may be disposed along a second side of the polygonal backbone, different from the first side.

An ion implanter, including an ion source and extraction system, arranged to generate an ion beam at a first ion energy, and a linear accelerator, arranged to accelerate the ion beam to a second ion energy, wherein the linear accelerator comprises a plurality of acceleration stages coupled to receive a plurality of RF signals from a plurality of power assemblies, respectively. The linear accelerator may be configured wherein at least one stage of the plurality of acceleration stages is coupled to: reversibly connect to a first power assembly, comprising a resonator that contains a resonator enclosure, the first power assembly generating a first RF signal at a first frequency; to disconnect from the first power assembly; and to connect to a second power assembly, generating a second RF signal at a second frequency, greater than the first frequency, while not changing the resonator enclosure.

A beam transport system for transporting a charged particle beam, includes a magnetic field generation device that is provided in a transport line that transports the charged particle beam and generates a magnetic field parallel to a center orbit of the charged particle beam, and a beam shielding device that is provided in a region through which the charged particle beam in the magnetic field generation device passes, causes a charged particle beam in a predetermined range of the charged particle beam to pass through, and stops other charged particle beams.

An ion implanter, including an ion source and extraction system, arranged to generate an ion beam at a first ion energy, and a linear accelerator, arranged to accelerate the ion beam to a second ion energy, wherein the linear accelerator comprises a plurality of acceleration stages coupled to receive a plurality of RF signals from a plurality of power assemblies, respectively. The linear accelerator may be configured wherein at least one stage of the plurality of acceleration stages is coupled to: reversibly connect to a first power assembly, comprising a resonator that contains a resonator enclosure, the first power assembly generating a first RF signal at a first frequency; to disconnect from the first power assembly; and to connect to a second power assembly, generating a second RF signal at a second frequency, greater than the first frequency, while not changing the resonator enclosure.