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7 July 1993 Mass spectrograph for imaging low-energy neutral atoms
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We describe an instrument concept for measuring low energy neutral H and O atoms with kinetic energies ranging from about 10 eV to several 100 eV. The instrument makes use of a low work function surface to convert neutral atoms to negative ions. These ions are then accelerated away from the surface and brought to an intermediate focus by a large aperture lens. After deflection in a spherical electrostatic analyzer, the ions are post accelerated to approximately 25 keV final energy into a time-of-flight mass analyzer. The latter consists of a thin carbon foil at the entrance that provides the secondary electrons for the start signal, a drift space, and a stop microchannel plate that detects the primary particles. Mass resolution is adequate for resolving H, He, and O, and the isotopes D and 3He. The image created by the spherical electrostatic analyzer is arc shaped with initial incident direction dispersed in azimuth and energy dispersed radially. Energy and azimuth information are obtained by position imaging the secondary electrons produced at the foil. A large geometric factor combined with simultaneous angle-energy-mass imaging that eliminates the need for duty cycles provide the necessary high sensitivity. From a spinning spacecraft this instrument is capable of producing a two-dimensional map of low energy neutral atom fluxes.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Arthur G. Ghielmetti, Edward G. Shelley, Stephen A. Fuselier, Federico A. Herrero, Mark F. Smith, Peter Wurz, Peter A. Bochsler, and Thomas S. Stephen "Mass spectrograph for imaging low-energy neutral atoms", Proc. SPIE 2008, Instrumentation for Magnetospheric Imagery II, (7 July 1993);


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