Patent GB-872174-A (GB)
Title: Improvements in spectrum analysis apparatus
IPC: G01N21/67
Filed: 1957-11-07
Abstract: 872,174. Photo-electric spectrometers. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. Nov. 7, 1957 [Nov. 9, 1956], No. 34770/57. Class 40(3) [Also in Groups XX, XXIX and XL(a)] The apparatus comprises a cylindrical casing having at least two apertures and carrying a rigid plate secured to which is a support extending towards the outside through one aperture 0 carrying means forming an extreme slit which is surrounded by a gas-tight cap fitted over said one aperture. This cap supports a spark producing device including 2 electrodes and a piece of insulating or semi-conducting material disposed therebetween. Within the casing is a diffraction grating which diffracts the rays from the entrance slit towards the second aperture on which is fitted a gas-tight housing accommodating a photographic or photo-electric analyzer. In use, a vacuum is created within the casing. The apparatus shown in Fig. 7 employs a photographic film as the radiation detector and comprises a cylindrical casing 24 with inwardly concave and walls of which the latter communicates with a pump so that the interior of the casing may be evacuated. Mounted at three points in the casing is a rigid plate 30 and flanges 27, 28, 29 which project from apertures in the cylindrical wall of the casing are used to define three chambers. One chamber houses the radiation source 9 and the entrance slit 35; another houses a concave diffraction grating 36 and the third houses a photographic film holder, the slit, grating and film being on the Rowland circle 37. The radiation source is disposed in a chamber 42 defined by an end cap attached to flange 28 and is provided by a spark which travels along an insulator or semi-conductor support located between two electrodes (see Group XL(a)). The entrance slit 35 is disposed on the Rowland circle 37 as shown in Fig. 7 in the same chamber as the radiation source. Attached to the plate 30 is a tube 62 which extends from inside the casing 24 through the apertures defined by flange 28 into the spark chamber 42 and is connected to the flange by bellows 77. Slidable in a recess in tube 62 is a gas tight valve, operable from outside the chamber, so that the latter may be opened to the atmosphere by means of a door 61 without destroying the vacuum in the rest of the apparatus. The slit itself is formed between two plates 63 and 64, Fig. 12, and the slit width is adjustable by an eccentric 65 operable from outside chamber 42. The plates 63, 64 are mounted on tube 62 by a plate 67 which is rotatable about the tube axis by a screw 69 to alter the direction of the slit. A rotatable shutter 78 is also provided to cut off the radiation from the spark when required. The diffraction grating 36 is disposed on Rowland circle 37 in the chamber defined by flange 27 and its end cap. It is concave and is adjustably mounted on a support carried by the rigid plate 30. The photographic film holder is disposed in the chamber defined by flange 29 and its end cap and comprises two concave surfaces (not shown) between which a film is clamped so as to lie on the Rowland circle 37 through slit 35 and grating 36. The holder is carried by a plate 84, as shown in Fig. 7, which is movable in slideways so that several images can be recorded on one film. The holder and the parts carrying it are rotatable about a point 38 on the Rowland circle by a screw 84a. A slit shutter is mounted in front of the film holder. The chamber may be closed to the inside of casing 24 by a gas-tight valve (see Group XXIX), so that the end cap may be removed to allow handling of the film holder. Instead of photographic film being used as detector a photo-electric device may be employed. This photo-electric device includes (as shown in Figs. 9 and 16) a plurality of slits 101 carried by a part 100 so that the slits lie on the Rowland circle 37, the part 100 being rotatable by screw and nut means on a plate 102 about an axis passing through point 38 of the Rowland circle. Plate 102 is mounted on curved guides on a plate 107, fixed to the rigid plate 30 in casing 24, so that by screw and nut means, the plate 102 and the parts carried thereby can be slightly rotated relatively to plate 107 about the centre of the Rowland circle. The slits are arranged in a gastight container 110 fixed to the flange 29 and on to the container is fixed another container 112. In the latter are disposed oppositely inclined fluorescent screens 115a, 115b (Fig. 16) on which the radiation from the slits is incident. The light from the screens passes through glass window in container 112 to photo-electric cells located outside. Radiation not deflected by the screens 115a, 115b is incident on flourescent windows at the rear of the container 112.