Patent GB-870867-A (GB)
Title: An apparatus for the evaluation of x-ray photographs of fine structure of materials
IPC: G01N23/205
Filed: 1958-05-30
Abstract: 870,867. Mechanical calculating-apparatus. KHOL, F. May 30, 1958 [May 31, 1957], No. 17339/58. Class 106 (1). The device described in Specification 824,994 for determining the crystal lattice parameters d corresponding to lines on an X-ray photograph of the Debye-Scherrer type is provided with additional apparatus whereby X-ray photographs of the back reflection type may also be analysed. As in the prior arrangement, an arm P is pivoted at the centre O 1  of a transparent drum D having a radius double that of the camera in which the photograph was exposed. A Debye-Scherrer photograph is placed in the drum and by means of a sight V the arm P is aligned with a chosen line on the photograph. The arm P then makes an angle # with its zero position Po, where # is the glancing angle in Bragg's equation, sin # = #/2d. A cursor N is then moved to intersect the appropriate one of a set S 1  of lines parallel to the zero line Po and at distances therefrom corresponding to various values of #/2 for different characteristic wavelengths of radiation. The value d may then be read from a scale on the arm P by means of the cursor N. A cursor N 1  co-operates with a scale of angles S. The present apparatus also includes a transparent holder Z for back reflection photographs which include lines produced by a reference substance, e.g. gold, having a known parameter d. The holder Z is of similar form to the chamber in which the photograph was taken. Also, three arms P 1 , P 2  and P 3  of equal length are pivoted at a point O 2  spaced from the centre O 1  by an amount equal to the length of the arms. The arms P 1  and P 2  are coupled by a linkage so as to move equally from the centre line O 1 , O 2 . The arms P 1 , P 2  and P 3  have sights V 1 , V 2  and V 3  for viewing the lines of the photograph so that an arm can be aligned with a line passing from the point O 2  through a selected line of the photograph. A further set S 2  of lines is provided, these again being parallel to the line Po and at distances therefrom corresponding to various values of #/2 for different characteristic wavelengths. Initially, the arm P is set by positioning the cursor N in accordance with the known value of d for the reference substance and then bringing it into coincidence with the appropriate line S 2 . The arm P then makes an angle #r + 90‹ - #r with the line O 1 , 02, 6r being the glancing angle for the reference substance. Then, the arms P 1  and P 2  are adjusted until the sight in the arm P 2  intersects the radial line of the arm P. To facilitate this, the cursor N may first be placed over the intersection of the radial line of the arm P with the circle described by the sights V 1 , V 2  and V 3 . Since O 1  is also on this circle, the arms P 1  and P 2  now make an angle 2#r with the extension of O 1 , 0,. The holder Z carrying the photograph is then adjusted along the line O 1 , O 2  and perpendicularly thereto until the symmetrical lines produced by the reference substance are centred in the sights V 1 , V 2  respectively. Then the arm P 3  is moved until a line under investigation is centred in the sight V 3 . The arm P is then adjusted so as to intersect the sight V 3  whereupon it makes an angle #, corresponding to the unknown substance, with the line O 1 , O 2 . When the cursor N is moved to intersect the appropriate line S 2 , the desired value d may be read from the scale on the arm P since d = #/2 coon. The lines S 1  and S 2  may be moved out of parallelism with the line Po in order to correct for absorption in a tube containing the sample. The drum D for holding Debye-Scherrer photographs is now adjustable along a line at 45 degrees to the line Fo.