Ion source refinement at VERA

This paper describes various modifications implemented at the 40-samples MC-SNICS Cs sputter source used at VERA. The pneumatic sample changer was replaced with a stepper motor drive, and also the adjustment collar for the vertical target wheel position was motorized. These two modifications allow now an automatic scanning of the target position with respect to the Cs-sputter beam. It also opens the way to use sample wheels holding more than 40 sample positions while keeping the original dimensions of the wheel. In order to hold the negative ion output constant, the control computer now regulates the Cs-capillary heater while the Cs-oven heater power supply stays fixed. Another modification was the replacement of the original conical ionizer with a spherical one, involving the enlargement of the diameter of the Cs-focus lens. This modification almost doubled the source output. To adapt the new ion optical geometry, we mounted a shield electrode in front of the target.