Medium Energy Ion Mass Spectrometer Capable of Measurements of Three-Dimensional Distribution Functions in Space

We have developed a new energy/mass spectrometer for medium energy range (10-200 keV/q) ion measurements in the Earth's magnetosphere and interplanetary space. The wide field-of-view ( ~360deg fan) enables acquisition of 3-D distribution functions for all the major ions, by utilizing spacecraft spin motions. The g-factor is much larger than the previous ion mass spectrometers in the medium energy range. The mass analysis unit that measures ion time-of-flights is well designed to realize a lightweight and simple signal processing. Laboratory experiments with a test model show that the performance of mass spectroscopy agrees with numerical simulations. Medium energy ion mass spectrometer with this new design will surely be useful for upcoming space missions in the inner magnetosphere, reconnection regions, and other energetic plasma structures/phenomena in space.