The measurement of x-ray intensities by means of Ross filters and photographic films

X-ray intensity measurements in a narrow range of the spectrum can be achieved by means of Ross filters. Nearly always they are used in connection with ionization detectors (especially pulse counters). With regard to certain applications, however, the employment of photographic film is of great interest, e.g. in microradiography or diffraction studies on amorphous materials. If the Ross-filter technique is combined with the photographic method instead of the counter method, the random error (arising from variations of the thickness or the speed of the emulsion, from nonuniform development, the graininess, etc.) becomes of paramount importance. Its dependence on filter thickness and X-ray voltage is discussed for Ni-Co and Zr-Sr filter pairs. Practical rules, which take into consideration the random error, as well as the error of monochromatism, are given.