GB887704A - Improvements in devices for measuring wave-lengths of x-rays - Google Patents

Abstract

887,704. X-ray diffraction apparatus. PHILIPS ELECTRICAL INDUSTRIES Ltd. Dec. 1, 1959 [Dec. 4, 1958], No. 40795/59. Class 98(1). Diffraction apparatus comprises an X-ray source, a diffracting crystal positioned in the X-ray beam and sufficiently thin for part of the beam to be transmitted through it, a part only being diffracted, means for guiding both transmitted and diffracted beams along different paths back to the same detecting device, and means for varying the length of at least one of said paths. This produces a variation in intensity at the detector, and by measuring the variation in path length required for two successive intensity maxima, the wavelength # of the incident X-radiation can be measured without having to measure the diffraction angle #. In Fig. 1, the X-ray beam strikes the crystal 2, part being transmitted directly 5 and part being diffracted 3. Further crystals 4, 6 reflect back to crystal 2 the diffracted and transmitted rays respectively, these rays then passing crystal 2 once more to be received by the detector 7. Displacement of crystal 6 as shown will vary one path length only. Due to consequent phase variation, the intensity of the combined radiation from both paths at the detector will also vary. By measuring the displacement of crystal 6 required for successive intensity maxima, the required wavelength # is determined. Fig. 4 shows another embodiment using four crystals. Crystals 10, 11 are moved together as shown to alter one path length. Fig. 6 shows a suitable mechanism for moving the crystals, which are carried on supports 16, 17 guided to move in slides 18, 19. They are rigidly connected by members 20, 21 to a frame 22 movable by a shaft 23. The end 28 of the shaft is guided in a spiral groove 29 in a gear-wheel 30 driven by a worm wheel 25. Figs. 3 and 5 (not shown) illustrate other path arrangements using four crystals and Fig. 2 (not shown) an arrangement using six crystals.