An analyzer for separating ions according to their time of flight comprising two opposing ion mirrors abutting at a first plane, each mirror comprising inner and outer field-defining electrode systems elongated along an analyzer axis, the outer field-defining electrode system surrounding the inner field-defining electrode system. The outer field-defining electrode system of one mirror comprises two sections, the sections abutting at a second plane, comprising a first section between the first plane and the second plane, and a second section adjacent to the first section. The first section has at least a portion which extends radially from the analyzer axis a greater extent than an adjacent portion of the second section at the second plane. The outer field-defining electrode system comprises an exit port and the analyzer comprises a detector located downstream of the exit port.
