System, apparatus and method for multi-frequency resonator operation in linear accelerator

A method of operating a linear accelerator, comprising:

• directing a first ion beam through a drift tube assembly, the drift tube assembly, comprising:
• a first drift tube electrode, coupled to a first output end of a resonator;
• and
• a second drift tube electrode, coupled to a second output end of the resonator and separated from the first drift tube electrode by a first gap;
• delivering a first radio frequency (RF) signal to the resonator at a first frequency, the first frequency representing a second Eigenmode of the resonator;
• directing a second ion beam through the drift tube assembly, the second ion beam comprising a second mass/charge (M/q) ratio, wherein the first ion beam comprises a first M/q ratio, less than the second M/q ratio;
• and
• delivering a second RF signal to the resonator at a second frequency, the second frequency representing a first Eigenmode of the resonator,
• wherein at the first Eigenmode frequency:
• a first voltage V1 at the first drift tube electrode is π radians out of phase with a second voltage V2 of the second drift tube electrode;
• and
• wherein at the second Eigenmode frequency:
• a voltage at the first drift tube electrode has a same magnitude and a same polarity as a voltage at the second drift tube electrode.

A high energy ion implantation system, comprising:

• an ion source and extraction system, arranged to generate an ion beam at a first energy;
• a linear accelerator, disposed downstream of the ion source, the linear accelerator arranged to accelerate the ion beam to a second energy, greater than the first energy, wherein the linear accelerator comprises a plurality of acceleration stages;
• and
• an RF power system, comprising a plurality of RF power assemblies, and arranged to output a plurality of RF signals individually to the plurality of acceleration stages;
• wherein the RF power system comprises an RF voltage source and a controller that is arranged to send a first RF signal to the linear accelerator corresponding to a first Eigenmode frequency for a first resonator of the plurality of acceleration stages, and to send a second RF signal to the linear accelerator corresponding to a second Eigenmode frequency for a second resonator of the plurality of acceleration stages, wherein, for a given resonator of the first resonator and the second resonator:
• at the first Eigenmode frequency, a first voltage V at a first drift tube electrode is π radians out of phase with a second voltage V2 of a second drift tube electrode;
• and
• at the second Eigenmode frequency, an oscillating voltage at the first drift tube electrode has a same magnitude and a same polarity as an oscillating voltage at the second drift tube electrode.