There are several principles for accelerating particles. Each corresponds to an accelerator family. Because particles trajectory radius and frequency are variable, they need a lower electric field to reach the same energy as cyclotrons. Higher energies are available with the same electric field. The essential part of the beam gets out by the extraction channel to the treatment room.
Magnet focuses the beam all along the beam path.
At the end of the beam path the particle has a very thin energy spectrum. In this case, particles travel through a distance of 3 cm in biological tissus. At C. P.O. the energy is closed to 200 MeV, which allows to treat lesions up to 22 cm deep in water equivalent tissues.