Dept. of Applied Physics
Oregon Graduate Center
It has been recently observed that the virtual source size and energy spread increases with current for liquid metal ion sources. It is important to know how the energy spread and virtual source size depend on all of the experimental parameters. The Monte Carlo method was employed to simulate the natural emission process for a liquid metal ion source. Each of the ions was traced from a spherical emitter to a final reference plane while under the influences of the spherical accelerating field and the mutual interactions of the other ions. At the final reference plane the velocities and positions were determined. From these values the final energy spread and virtual source size were obtained. To find the functional dependence of all of the experimental parameters, the program was rerun varying one parameter at a time over a specific range of values. The experimental parameters investigated were: current (I), mass (M), charge (q), emitter radius (a), field at the emitter surface (F), distance traveled by the ions (Z), emission angle (Î±), initial kinetic energy, and initial energy spread of the ions. In the final analysis, the functional dependence of the energy spread ÎE and the virtual source diameter d, on the various parameters was found to be dimensionally consistent.[Equations in original document were omitted.] The virtual source size and final energy spread were found to have no dependence on the initial kinetic energy, and the virtual source size was also found to be independent of the initial energy spread. The final energy spread, however, was found to be proportional to the initial energy spread.
Hoepfner, Patrick J., "A Monte Carlo calculation of virtual source size and energy spread for a liquid metal ion source" (1985). Scholar Archive. 73.