Ion current density profile control of a scalable linear ion source and its application

Abstract

We present a modular microwave excited electron cyclotron resonance type linear ion source concept that allows the adaptation of the ion beam dimensions to the requirements of the particular application. The ion beam current density profile is controlled by dividing the middle grid of a triple-grid system into segments of 2cm width. Each segment is separately switched between the negative accelerator grid voltage and a positive blocking voltage. By adjusting the pulse-to-pause ratio of each segment, the current density profile can be controlled from a homogeneous profile up to nearly arbitrary profiles. This ion source enables an in situ adaptation of ion beam profile. The application of a 2m linear ion source for hardening of stainless steel tools and the homogenization of the beam profile by segmented grids are demonstrated.