Ion emission simulations of the nano-aperture ion source

The main goal of this chapter is demonstrating realistic simulations of the nano-aperture ion source. The optical effects due to the electric fields, the ion-neutral scattering, and Coulomb interactions are studied simultaneously using Monte-Carlo ray tracing. Two rather unusual coulomb-interactions were taken into account, namely, surface induced charge, and electron-ion scattering. Ion-to-ion coulomb repulsion is found to pose an ultimate limit to the achievable brightness. The effect is relevant inside the chip, but also in the region where the beam is accelerated up to high voltage.In a realistic configuration the simulations predict a brightness of about 3 × ^{10 6} A/m² srV in combination with an energy spread of 1 eV. Interestingly, the attainable brightness is not very sensitive to the geometry, nor was it very dependent on the noble gas species. To achieve the best performance, electric fields close to 10 kV/mm should be used, inside and outside of the gas chamber.