Abstract
Some components of the r-ray radiography system still leave much to be investigated with respect to the response functions of the system. A few of those components are the source, object, intensifying screen and film. The present paper describes a new method of measuring the response to 7-rays by a combination of X-ray film and Pb screen which is another component of the 7-ray radiography system.
A wedge which absorbs 7-rays is moved back and forth in the way that its displacement is sinusoidal; thus penetrating 7-ray doses vary with time by the sine wave. The film is moved at a constant velocity across such a 7-ray beam, so that nearly sinusoidal patterns are developed upon the film as stripes. The contrast of light and shade in the strip patterns determines the response functions of the film combination. In this experiment, the depth of the 7-ray absorption varies sinusoidally but 7-ray dose variations on the film show an exponentially modulated sine wave.
The difference between the blackness made by the genuine sine wave and that by the modulated wave and also the relation between response functions of both cases were investigated by means of Fourier expansion. The result showed about 1.5% and 5% differences in the blackness and the response value respectively. A collimated γ-ray beam was required in the experiment. In order to obtain the collimated beam, slits with narrow width were used. A correction term √1-cos2πνW/√2πνW was found where W is the width of the slit.
