A double-focusing toroidal mass spectrograph for energetic plasmas: I. First-order theory
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment(1987)
摘要
A conceptual design for a new type of ion mass spectrograph is presented that is particularly suited for measuring energetic (1 eV to 50 keV/charge) anisotropic space plasmas. The ion optics consist of two toroidal electrostatic analyzers followed by a combined toroidal electric-magnetic sector field. The resultant Mattauch-Herzog type configuration exhibits double-focusing properties for all masses along an oblique line exterior to the magnetic field. Although the focusing properties vary with ion energy, particular field geometries exist which minimize this energy dependence. As a result, good mass resolution and high sensitivity can be maintained over a wide energy range. Mass resolution is adequate to resolve mass/charge values (1, 2, 4, 8, 16) at all energies and can be increased to > 20 in specialized low-energy ( < 5 keV) modes. The spectrographic mass imaging range is > 16 amu at energies above 10 keV. The toroidal geometry focuses in elevation direction, thus minimizing overall instrument and detector sizes while providing limited angular resolution in that direction. Large beam acceptances result in very high overall instrument sensitivity (geometric factor ∼ 10−2 cm2 sr keV).
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关键词
conceptual design,magnetic field,first order
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