a modified cyclotron in which the frequency of the accelerating voltage is modulated to take into account the increase in the relativistic mass of the particle as it reaches high energies
See synchrocyclotron in American Heritage Dictionary 4
noun
A cyclotron that accelerates protons and positive ions by using frequency modulation to synchronize the phase of the accelerating potential with the frequency of the accelerated particles to compensate for relativistic increases in particle mass at high speeds.