The isochronous cyclotron: principles and recent developments.

The principals of a cyclotron are described. A magnetic field guides the ions in circular paths, while an electric field accelerates them. The main problem in any accelerator is not to accelerate ions, but to focus them. An isochronous cyclotron overrules the problems related to relativistic mass increase during acceleration. Harmonic operation and negative (vs positive) ion acceleration (and extraction) are explained, as they make dedicated PET cyclotrons a simple, reliable, and suitable tool. The characteristics of such PET cyclotrons are described, as well as their technical implementation. The IBA 18/9 PET cyclotron is given as an example.