Abstract: High energy resolution at high electron current at the specimen or at the detector is obtained by an electron beam guiding with focusing energy selection, in particular in an electron spectrometer with emission system and at least one energy dispersive system with different focusing in two mutually perpendicular directions, by a non-circular-symmetrical lens system placed after or before the energy dispersive system and correcting the different focusing of the electrons in the two mutually perpendicular directions such that either the virtual or the real entry stop of the energy dispersive system is imaged on an accessible image plane outside the energy dispersive system or an object outside the energy dispersive system is imaged on the virtual or real exit stop of the latter.

Abstract: Disclosed is an entrance system having an image angle of 180.degree. suite for a radiation detector for detecting differing wavelengths of sunlight, comprising a hemispherical shell of light transmitting material; a tube of light transmitting material extending coaxially from the hemispherical shell; a granulated light scattering medium containing inside the hemispherical shell; and a stepped body of light transmitting material inserted into the tube, the stepped body having an end which terminates in at least three steps and which abuts against the granulated medium and seals the medium in the hemispherical shell.