The Lorentz Electron and Ion Analyser (LEIA) – An Instrument Prototype for Low-Contamination Particle Measurements

Plasma Observatory is a candidate mission of the European Space Agency (ESA), with a potential launch in 2037. It aims to investigate plasma coupling across multiple scales in the Earth’s magnetosphere.Energetic ions and electrons are sensitive tracers of plasma acceleration and transport processes. This makes high-cadence in situ measurements essential for understanding magnetospheric dynamics. On Plasma Observatory, such measurements will be provided by the Energetic Particle Experiment (EPE). The instrument utilizes the well-proven foil–magnet technique to separate electrons from ions and covers an energy range from 30 keV to 600 keV.In this contribution, we present a novel instrument prototype, the Lorentz Electron and Ion Analyser (LEIA). The concept is based on an earlier, alternative design developed in the context of Plasma Observatory, but is independent of the currently baselined EPE instrument and not intended for flight on Plasma Observatory. It uses a single-channel approach, separating particles by means of a finely tuned magnetic field as well as a modified dE/dx-E detector stack. No foil is used.This design aims to enable advanced particle species discrimination while significantly reducing electron–ion cross-contamination. Although LEIA is presented as a concept study rather than a mission-specific instrument, it demonstrates a promising pathway for future energetic particle measurements in magnetospheric and heliospheric science missions.