An instrument which can separate selected ion beams with fields which do not vary with time. The fields are generally both electric and magnetic.
Sources: Orange Book, 2nd ed., p. 202 [Terms] [Book] PAC, 1991, 63, 1541. (Recommendations for nomenclature and symbolism for mass spectroscopy (including an appendix of terms used in vacuum technology). (Recommendations 1991)) on page 1546 [Terms] [Paper]