Cyclotron that achieves relativistic velocities by modulating the frequency of the accelerating electric field WordNet 3.0 & Open English WordNet

A synchrocyclotron is a special type of cyclotron, patented by Edwin McMillan in 1952, in which the frequency of the driving RF electric field is varied to compensate for relativistic effects as the particles' velocity begins to approach the speed of light. Wikipedia

Special type of cyclotron Wikidata

A particle accelerator like a cyclotron, but which operates at variable frequency to account for the particles gaining energy, allowing for greater energies to be achieved. Wiktionary

Particle accelerator. Wiktionary (translation)