A Hot Plasma Composition Analyzer for the Magnetospheric Multiscale Mission

We have designed and built a prototype of a hot plasma composition analyzer (HPCA) that has applications to in situ space plasma physics in general and the Magnetospheric Multiscale Mission in particular. The HPCA is based on a toroidal top-hat energy-angle analyzer coupled to a time-of-flight mass analyzer based on the carbon foil technique. Using analytical methods we optimized the HPCA for transmission, dynamic range and mass resolution sufficient to measure and resolve all relevant major ion species (H+, He++, He+ and O+) found in the solar wind and Earth's magnetosphere. The design takes into consideration optimum matching of energy-angle and time-of-flight analyzers. Dynamic range issues are addressed in a novel way using an RF waveform applied to the energy analyzer. We have obtained improved ion mass resolution compared to earlier instruments of this type by spatially resolving scattered ions and neutrals exiting the carbon foil of the time-of-flight (TOF) analyzer and using that information to correct the TOF spectrum.