A novel planar ion funnel design for miniature ion optics

The novel planar ion funnel (PIF) design presented in this article emphasizes simple fabrication, assembly, and operation, making it amenable to extreme miniaturization. Simulations performed in SIMION 8.0 indicate that ion focusing can be achieved by using a gradient of electrostatic potentials on concentric metal rings in a plane. A prototype was fabricated on a 35 × 35 mm custom-designed printed circuit board (PCB) with a center hole for ions to pass through and a series of concentric circular metal rings of increasing diameter on the front side of the PCB. Metal vias on the PCB electrically connected each metal ring to a resistive potential divider that was soldered on the back of the PCB. The PIF was tested at 5.5 × 10⁻⁶ Torr in a vacuum test setup that was equipped with a broad-beam ion source on the front and a micro channel plate (MCP) ion detector on the back of the PIF. The ion current recorded on the MCP anode during testing indicated a 23× increase in the ion transmission through the PIF when electric potentials were applied to the rings. These preliminary results demonstrate the functionality of a 2D ion funnel design with a much smaller footprint and simpler driving electronics than conventional 3D ion funnels. Future directions to improve the design and a possible micromachining approach to fabrication are discussed in the conclusions.