A DESIGN OF LARGE CURRENT ION GUN EMPLOYING LIQUID-METAL ION-SOURCE

A lens system for a large current liquid metal ion source has been designed by a numerical computer simulation method. As a computed result, the lens system can focus an ion beam having an emission angle of 60°to a beam having a radius of 1.8 mm at 1 m from the ion source. Following the simulated result, the lens system was constructed and tested. When the total ion current extracted from the ion source was less than 10 μA, more than 95% of the total ion was focused to a beam with a radius of about 2 mm at 1 m from the ion source, which agreed well with the computer simulation result. When the total ion current became more than 10 μA, the minimum radius of the focused ion beam at 1 m from the ion source gradually increased with it. However, even if the total ion current was more than 50 μA, almost 80% of it could be obtained on a 1×1 cm2 target at 1 m from the ion source.