Uniform target irradiation by circular beam sweeping

A circular sweep of the beam over a large target for making a uniform irradiation zone is suggested. The scan pattern is an untwisted spiral for a continuous beam or a family of concentric circles for a bunched beam. The deflection voltage is provided by RF cavities with orthogonal transverse fields shifted in time by π/2. The amplitude of the deflection voltage as a function of time and the optimal beam scan frequency with respect to the RF frequency of the accelerator are given. The considered method of target irradiation can be useful in different applications of charged particle beams including microfilter production and transmutation of nuclear wastes where a large amplitude of the deflection voltage and a high uniformity of irradiation are required. (orig.)