Non-linear beam optical calculations and measurements for a sputter negative ion source

This paper describes a simple and rapid method for calculating the non-linear optical properties of a negative ion beam from a sputter-type source model 860. The calculation includes the space charge effects and non-linear aberrations. The beam envelope and the distorted emittance ellipses are obtained using the method of tracing ray trajectories. A 50 % increase in beam emittance was found due to aberrational effects when the ion beam goes through a strong decelerating-accelerating Einzel lens. The space charge effects are small over the range of intensities investigated (0<I<50*10-6 A). Measurements were performed on a test bench using the same model 860 negative ion source. The calculated results are roughly consistent with the measurements. Therefore, more reliable starting conditions than can be obtained from linear calculations are now available to design the downstream transport system