World trends in cyclotron developments for nuclear physics and applications

Today, the number of cyclotrons operating in the world largely exceeds 200. The field of uses covers production of radioisotopes for medicine, therapy by neutron and ion beams, nuclear, atomic and solid state physics research, material analysis and radiation damage studies, and production of intense neutron beams for present and future purposes. Despite this diversity, continuing efforts driven by both research laboratories as well as commercial firms result in a series of improvements in the various techniques used in the design and operation of cyclotrons. This paper intends to draw the main directions of evolution in the following issues: injection and extraction systems, beam dynamics (including high intensity issues), magnetic and electric fields computation, as well as existing and possible future applications in medicine, production of energy, neutron spallation sources and transmutation technologies. The question of a possible resurrection of FFAG (Fixed-Field, Alternating Gradient) cyclotrons, a concept invented in the fifties, will be shortly brought up.