Certain embodiments described herein are directed to reflectron assemblies and methods of producing them. In some configurations, a reflectron comprising a plurality of lenses each comprising a planar body and comprising a plurality of separate and individual conductors spanning a central aperture from a first side to a second side of a first surface of the planar body is described. In some instances, the plurality of conductors are each substantially parallel to each other and are positioned in the same plane.