PROCEDE ET APPAREILLAGE D'ANALYSE SPECTROMETRIQUE A RAYONS X

1422330 Electron microscopes SOC NATIONALE DES PETROLES D'AQUITAINE 29 Dec 1972 [29 Dec 1971] 33711/75 Divided out of 1422329 Heading H1D [Also in Division H5] Apparatus suitable for the method of X-ray spectrometric investigation of a sample described and claimed in Specification 1,422,329, in which the angle between an incident electron beam irradiating an extended area of the sample surface to excite X-rays, and the X-ray beam selected by the spectrometer collimator does not exceed 40 degrees, includes a glow discharge tube as the electron source. The arrangement of Fig. 4b includes a pair of similar glow tubes (one only shown in full) detachably mounted in a frame 26 one either side of a collimator 1. The spacing between the cathode 20 and the anode 21 is adjustable by sliding portion 22 within portion 25, and gas exit and entry ports 23 and 24 are provided. In Fig. 5 the glow tube has an annular aluminium cathode 2 and mesh grid anode 3, which surrounds a collimator 1; to prevent excessive irradiation at the centre of the irradiated area, the cathode emissivity may be reduced in the inward radial direction, either by forming the cathode of a succession of concentric annuli of differing materials, or by forming it of indented shape, Fig. 11 (and Fig. 10, not shown), and rotating it in use. In other arrangements the incident electron beam may be directed normal to the specimen and the X-ray beam may be inclined thereto; both the electron beam and the X-ray beam may be directed normal to the specimen by deflecting the electron beam by magnetic (Fig. 3a, not shown) or electrostatic means (Figs. 3b, 12 and 13, not shown); and intersecting incident beams may be employed to ensure that every point on the sample surface receives electrons from at least two different directions.