Nier–Johnson geometry

https://doi.org/10.1351/goldbook.N04141
An arrangement for a @D01845@ in which a deflection of $$\frac{\pi}{2}$$ radians in a radial electrostatic field analyser is followed by a magnetic deflection of $$\frac{\pi}{3}$$ radians. The electrostatic analyser uses a symmetrical object-image arrangement and the magnetic analyser is used asymmetrically.
Sources:
Orange Book, 2nd ed., p. 201 [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]