Fabrication of chopper for particle beam instrument

A technique for providing a grid for a gate such as utilized in gating a stream of ions or other particles in a spectrometer instrument. The grid of wires may, for example, be a so-called Bradbury-Nielson Gate that consists of a set of two electrically isolated sets of equally spaced wires that lie substantially in the same plane and alternate in potential. The method utilized to provide is to first fabricate a frame of an insulating substrate having a hole and depositing metal film patterns such that conductive portions are formed on either side of the hole. Conductive portions on either side form a series of terminating pads on the portion of the substrate closest to the hole and a bus bar. Grid wires are then formed by stretching a section of wire with desired constant tension across the hole and bonding the ends of the wire to a respective one of the pads on one side and bus bar on the other side. The method provides a rapid, inexpensive way to fabricate such modulating devices.