Standing wave particle beam accelerator

An accelerator for accelerating a particle beam includes a main body having a plurality of electromagnetic cavities coupled in series, and a first coupling body having a first side cavity coupled to one of the electromagnetic cavities through a first opening, and to another of the electromagnetic cavities through a second opening, wherein the first opening and the second opening have different configurations. The accelerator further includes a pair of conductive capacitively coupled noses secured to side walls of the first coupling body, wherein the pair of noses have equal lengths.