Patent GB-974392-A (GB)
Title: Apparatus for x-ray fluorescence emission analysis of elements in a pulp or slurry
IPC: G01N/
Filed: 1962-10-10
Abstract: 974, 392. Analysis of elements in pulp or slurry, using X-rays. RHOANGLO MINE SERVICES Ltd. Oct. 10, 1962 [Oct. 11, 1961], No. 38332/62. Heading G1A. The invention relates to a method of an apparatus for X-ray spectrographic analysis of fluent materials in which a number of separate streams of materials are caused to flow along prescribed paths each path including a cell for presenting the stream of material in that cell to an analyser consisting of an X-ray tube, suitable collimators and analysing crystals, and relatively moving the cells and the analyser in timed sequence so that each cell in turn is presented to the analyser. As shown six cells 12-17 through which the materials to be investigated flow are mounted on a rotatable turntable 10 and in the position shown for the cell 12 are irradiated with X-rays from a tube 23. Two analysers 25 to detect secondary emission from the material in the cell being irradiated are provided so that two elements in the material may be analysed simultaneously, and each analyser consists of entrance and exit slits or collimators and analysing crystals which disperse the secondary X- rays the wavelengths of which are characteristic of the element to be analysed and allow the characteristic wavelengths to be diffracted on to a scintillator detector 26. The resultant output pulses from the detector are fed through an amplifier 27 to a counter 28 and to a ratemeter 29 which converts impulse signals from the counter to a D.C. signal which is applied to one of a number of recorders 30. each of which records the concentration of one element in the material. A servo system comprising a servomotor 33 coupled to the turntable 10, which together with a slide wire 34 operated by the motor 33, a potential divider 35 and a servo amplifier 36 forms a self balancing system under the control of a timing mechanism 37 which actuates a series of relays (not shown) to unbalance the servo system to cause the turntable to be rotated in such a manner that the cells 12. . . 17 are presented to be irradiated by the tube 23 in sequence. The relays also set the ratemeter 29 to an appropriate range by means of a range switching unit 31, select the appropriate recorder 30 and select an appropriate material density compensation circuit. The compensating circuit affects the intensity measurement derived from the scintillation detector 26 inversely according to the density of the material in the cell under investigation. The compensating circuit comprises a third scintillation detector 43 which receives that residuum of the primary X-ray beam which has passed through the cell under investigation. The output signal of the detector 43 is applied to an amplifier 44, a counter 45, a ratemeter 46 and from there to compensating networks 55 (Fig. 2 not shown) connected to the recorders 30 to apply a correction signal in accordance with the density of the material in the investigated cell. Suitable filters 61 are provided between the detector 43 and the investigated cell so as to provide a linear relationship between the intensity of the X-rays emerging from the cell and the density of the material therein. Adjustable iris attenuators 53 are situated in front of the detectors 26 and 43 in order to allow compensation for drift in the characteristics of the detectors. A cell 18 containing a standard sample of material may be brought to the investigation position by the actuation of a selector 51. In this position a recorder 52 may be switched to indicate the various output voltages of the ratemeters 29 or of the density compensation ratemeter 46.