A novel end‐loss ion‐energy spectrometer is designed for plasma‐ion diagnostics in open‐ended plasma‐confinement devices. This analyzer significantly upgrades a previous slanted grid end‐loss analyzer (SELA) to essentially eliminate secondary‐electron current, and to provide a differential‐spectrum mode of operation, in addition to the usual integral‐spectrum operation of gridded ion‐energy analyzers. The upgraded SELA does not perturb the ambient magnetic field due to its electrostatic operation. Either the differential or integral spectra are obtained by a time sweep of grid voltages, collecting the ion current on a single‐channel plate. Because the angular alignment of the SELA is not critical, it can be used as a spatially scannable diagnostic of ion‐energy distributions and plasma potentials. It is characterized using computer simulations of ion trajectories, monoenergetic ion beams, and end‐loss plasma from the world’s largest tandem mirror—GAMMA 10. ©1995 American Institute of Physics.