A synchrocyclotron is a cyclotron 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. This is in contrast to the classical cyclotron, where the frequency was held constant.
The two fundamental differences between this machine and the orthodox cyclotron are that
in this machine, only one dee is used instead of two
Synchrocyclotrons have not been built since the isochronous cyclotron was developed.
Isochronous cyclotrons maintain a constant RF driving frequency and compensate for relativistic effects by increasing the magnetic field with radius. Isochronous cyclotrons are capable of producing much greater beam current than synchrocyclotrons.
The chief advantage of the synchrocyclotron is that there is no need to restrict the number of revolutions executed by the ion before its exit. As such, the potential difference supplied between the dees can be much smaller.
The smaller potential difference needed across the gap has the following uses:
There is no need for a narrow gap between the dees as in the case of convention cyclotron, because strong electric fields for producing large acceleration are not required. Thus only one dee can be used instead of two, the other end of the oscillating voltage supply being connected to earth.
The main drawback of this device is that, as a result of the variation in the frequency of the oscillating voltage supply, only a very small fraction of the ions leaving the source are captured in phase-table orbits of maximum radius and energy so that the output beam current is rendered weak. Thus the machine produces high energy ions, though of small intensity