Cyclotron dee

A hollow D-shaped electrode that shields a circulating ion from the accelerating electric field during one half-turn. Two opposed cyclotron dees provide two shielded regions separated by a gap; their electric potential difference alternates. The vacuum reduces collisions with residual gas. An ion source supplies particles near the center, and an extraction system directs an outer orbit toward a particle detector or target. Useful electric current depends on retaining particles near the median plane and delivering them to the outlet, as well as on increasing their kinetic energy.