Patent GB-899291-A (GB)
Title: An arrangement capable of being used as an electron microscope and for x-ray spectrometric examination
IPC: H01J37/252
Filed: 1958-09-26
Abstract: 899,291. Electron microscopes; X-ray spectrometers. LABORATOIRE SUISSE DE RECHERCHES HORLOGERES. Sept. 26, 1958 [Sent. 26, 1957], No. 30842/58. Class 98(1). [Also in Group XL(a)] An electron microscope has means for producing a fine electron beam and focusing it on an object, with means for detecting electrons passing through or reflected from the object, and an X-ray spectrometer so arranged as to receive X-rays produced as a result of the beam striking the object. The spectrometer may be enclosed completely within the vacuum space of the electron microscope, or alternatively connected structurally with it. In the arrangement of Fig. 1 the spectrometer is attached to the microscope and separated from it by an X-ray-permeable window. In this arrangement, electrons from a source 1 pass through magnetic lenses 2, 3 forming a condenser system and strike an object 4, in this instance a ray-permeable object. The beam then passes further through an object lens 5, an intermediate (magnification) lens 6 and a projection lens 7, finally forming an image on a viewing screen 8. The object 4 is inclined so that at the same time X-rays 10 produced by the impingement of the beam pass to a pulse generator 12 and shaper 13 to a synchroscope 14, on the screen of which an X-ray spectrum may be obtained. This form of the apparatus may thus be used for simultaneous electron-optical and X-ray spectrometric investigation of the same specimen. Fig. 5 shows a modification for use with ray-impermeable objects, the object 62 now being located beyond the projection lens 7. The beam is produced by lenses 2 and 7, the other lenses not being used. The surface of the object is irradiated with light from a source 68, which is reflected on to the object via mirror 70 and a semi-opaque mirror 65, each of which has an aperture for passage of the electron beam. The visible image is observed through an eye piece 64, which receives the light reflected from the object via a mirror objective 66, 67. (The surface of the components of the optical system may be rendered electrically conductive and biased with a constant voltage, to prevent the adherence of secondary particles). Two spectrometers 71, 73 are provided, each adjusted to a different range of wavelengths, and having associated crystals 72, 74. The arrangement of Fig. 5, in which the object is located beyond the last lens, can also be used with ray-permeable objects producing an image on a screen (Fig. 6, not shown). Fig. 7 shows an arrangement of adjustable specimen stage which can be controlled from outside the microscope, whose wail is shown as 91. The specimen is placed on a central stage portion 93 which is adjustable relative to a main stage 96 by screws 94, 95 acting against springs 97, 98. On stage 96 is mounted a rotatable table 99 carrying a plurality of comparator elements 100, any of which can be brought round into a preparatory position (as at 102) by screw 101, which rotates the table. Screw 101 also operates to displace the main stage axially against springs 103, 104, so that the central portion is displaced out of the beam path, and the comparator 102 brought into it.