A split grid multi-channel secondary particle detector for a charged particle beam system includes a first grid segment and a second grid segment, each having independent bias voltages creating an electric field such that the on-axis secondary particles that are emitted from the target are directed to one of the grids. The bias voltages of the grids can be changed or reversed so that each grid can be used to detect the secondary particles and the multi-channel particle detector as a whole can extend its lifetime.