Extracted-Beam Divergence Calculations for a Liquid-Metal Ion Source

The space-charge spreading of the beam in the ion-extraction region of a liquid-metal ion source is evaluated by calculating the ion trajectories. The rate of increase is the emission angle for the modified “Taylor cone” anode is expressed by a universal curve given by a function of (d I /dΩ) 0 M 1/2 /( V AC /α) 3/2 . Here, (d I /dΩ) 0 is the angular ion intensity on the anode surface, M is the atomic mass of a singly-charged ion, V AC is the difference in potential between the anode and the cathode, and α is a shape factor for the anode.