  Bradbury Nielsen gates are well known devices used to switch ion beams and
are typically applied in mass or mobility spectrometers for separating beam
constituents by their different flight or drift times. A Bradbury Nielsen gate
consists of two interleaved sets of electrodes. If two voltages of the same
amplitude but opposite polarity are applied the gate is closed, and for
identical (zero) potential the gate is open. Whereas former realizations of the
device employ actual wires resulting in difficulties with winding, fixing and
tensioning them, our approach is to use two grids photo-etched from a metallic
foil. This design allows for simplified construction of gates covering large
beam sizes up to at least 900\,mm$^2$ with variable wire spacing down to
250\,\textmu m. By changing the grids the wire spacing can be varied easily. A
gate of this design was installed and systematically tested at TRIUMF's ion
trap facility, TITAN, for use with radioactive beams to separate ions with
different mass-to-charge ratios by their time-of-flight.
