classical cyclotron

A classical cyclotron is a type of particle accelerator that uses a magnetic field to guide charged particles in a spiral path, increasing their energy with each revolution. Developed in the early 1930s, it was the first cyclic and resonance accelerator to produce particles energetic enough for nuclear research.12

The key principle is that the time it takes for a particle to complete an orbit is constant, regardless of its speed, as long as its speed is much less than the speed of light. This allows a high voltage, reversing polarity at a constant frequency, to accelerate the particle multiple times. Particles are injected at the center and accelerated across a gap between two D-shaped electrodes called dees. Each pass through the gap increases the particle's energy and the radius of its circular path, creating a spiral trajectory.12

The energy of particles in a classical cyclotron is limited by relativistic effects, where mass increases with speed, causing particles to fall out of sync with the accelerating voltage. This limits proton energies to below 25 MeV.12