Radio-frequency quadrupole

A radio-frequency quadrupole (RFQ) is a linear accelerator component[1] generally used at low beam energies, roughly 2keV[2] to 3MeV.

This causes the particles to form bunches in step with the exciting frequency, such that they pass through each region as the local field is near the acceleration maxima.

There are two common electrode shapes, either a group of 4 vanes with a wave pattern on the tips that approach, or 4 cylinders with periodic conical sections.

The electrodes are mounted in vacuum and excited from by suitably phased signals from a high power RF source.

Invented by Soviet physicists I. M. Kapchinsky and Vladimir Teplyakov in 1970, the RFQ is used as an injector by major laboratories and industries throughout the world for radiofrequency linear accelerators.