Production, acceleration and diagnostics of high intensity beams

Abstract

High current ion sources are usually defined by the increasing influence of space charge forces on the ion beam or in a more practical way by an ion current ≥ 10 mA for gas ion sources and ≥ 1 mA for metallic ions. Methods of metal ion production will be presented in relation to high current ion sources. Various ion sources have been developed for high current ion beams, like Duopigatrons, Freeman-, Multicusp-, μ-wave-, ECR- and Mevva-ion sources. These ion sources will be presented and discussed with their special features and typical area of applications. The maximum ion current density extractable from a high current ion source is proportional to U 3 2 , ( q A ) 1 2 and d −2 ( U is the extraction voltage, q A the ion charge to mass ratio, d the extraction gap width). Multiaperture extraction systems are frequently used for large area ion beam formation. Efficient beam formation of high current ion beams needs carefully designed extraction and acceleration systems to avoid emittance growth. The transport of high current ion beams is highly influenced by space charge effects. Compensation of the ion charge by secondary electrons from collisions with residual gas particles is a common method to reduce space charge forces in the ion beam. High current ion beams can deposit high power in the diagnosis instruments (and in the targets) and can easily destroy them by melting or sputtering. Careful design and efficient cooling is essential for beam-destructive diagnosis elements and nondestructive methods like beam transformers and pick up probes have to be implemented in many cases. Examples of high intensity diagnosis methods will be discussed.