The 3-D Plasma Distribution Function Analyzers With Time-of-Flight Mass Discrimination for Cluster, FAST, and Equator-S
Balsiger, H.; Klecker, B.; Kistler, L. M.; Rosenbauer, H.; Shelley, E. G.; Parks, G. K.; McCarthy, M.; Korth, A.; Möbius, E.; Réme, H.; McFadden, J. P.; Carlson, C. W.; Sauvaud, J. A.; Hovestadt, D.; Laeverenz, P.; Eliasson, L.; Jiang, Y.; Aoustin, C.; Cros, A.; Rouzaud, J.; Granoff, M.; Seidenschwang, E.; Ingraham, C.; Olsen, S.; Curtis, D.; Popecki, M. A.; Médale, J. -L.; Crocker, K. C.; Sartori, E.; Ye, V.; Camus, T.; Heetder, H.; Croyle, J.; Ertl, M.; Eberl, F.; Kästle, H.; Künneth, E.; Klumpar, D. M.; Hertzberg, E.; Gräve, B.; Schwab, U.; Steinacher, M.
United States, France, Sweden, Germany, Switzerland
Abstract
A similar time-of-flight plasma analyzer system will be flown as CODIF (COmposition and DIstribution Function analyzer) on the four Cluster spacecraft, as ESIC (Equator-S Ion Composition instrument) on Equator-S, and as TEAMS (Time-of-flight Energy Angle Mass Spectrograph) on FAST. These instruments will for the first time allow the 3-dimensional distribution functions of individual ion species to be determined within 1/2 or 1 spin period. This will be crucial for the study of selective energization processes in various regions of the magnetosphere. The sensor consists of a toroidal top-hat electrostatic analyzer with instantaneous acceptance of ions over 360° in polar angle. For Cluster and Equator-S this range is subdivided into two halves with geometric factors different by a factor of 100 in order to cope with the wide dynamic range of fluxes in the magnetosphere. For FAST the time resolution is increased by a factor of two to focus on fast auroral phenomena by using both halves simultaneously. After post-acceleration of the incoming ions by up to 25 kV, a time-of-flight mass spectrograph discriminates the individual species. It has been demonstrated in calibration runs that the instruments can easily separate H+, He2+, He+, O+ and for energies after post-acceleration of 320 keV even O+2 molecules. On board discrimination, accumulation, and moment computation allow efficient retrieval of the data stream.