Microtron

[1][2] The kinetic energy of the particles is increased by a constant amount per field change (one half or a whole revolution).

In a microtron, due to the electrons' increasing momentum, the particle paths are different for each pass.

This procedure can be repeated until the increasing radius of the particle's path makes further acceleration impossible.

The particle beam is then deflected into an experiment area or a further accelerator stage.

[3] Microtrons provide high-energy electron beams with a low beam emittance (no radiation equilibrium) and a high repetition rate (equal to the operation frequency of the linac).

Particles in a classic microtron get emitted from a source (blue), accelerated once per turn ( microwave cavity , gray), increasing their path radius until ejection.
Particles in a racetrack microtron, coming from an external source.