Synchrocyclotron

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.

In the synchrocyclotron, only one dee (hollow D-shaped sheet metal electrode) retains its classical shape, while the other pole is open (see patent sketch).

Furthermore, the frequency of oscillating electric field in a synchrocyclotron is decreasing continuously instead of kept constant so as to maintain cyclotron resonance for relativistic velocities.

multiplies the mass, such that where This is then the angular frequency of the field applied to the particles as they are accelerated around the synchrocyclotron.

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.

The smaller potential difference needed across the gap has the following uses: 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-stable orbits of maximum radius and energy with the result that the output beam current has a low duty cycle, and the average beam current is only a small fraction of the instantaneous beam current.

In 1945, Robert Lyster Thornton at Ernest Lawrence's Radiation Laboratory led the construction of the 184-inch (470 cm) 730 MeV cyclotron.

The first funding was in 1946 for Carnegie Institute of Technology to build a 435-MeV synchrocyclotron led by Edward Creutz and to start its nuclear physics research program.

[3] At a UNESCO meeting in Paris in December 1951, there was a discussion on finding a solution to have a medium-energy accelerator for the soon-to-be-formed European Organization for Nuclear Research (CERN).

In 1952, Cornelis Bakker led the group to design and construct the synchrocyclotron named Synchro-Cyclotron (SC) at CERN.

[4] Synchrocyclotrons are attractive for use in proton therapy because of the ability to make compact systems using high magnetic fields.