Abstract
Overall response function of the thickness gauging system composed of a radiation source and a ionization chamber is calculated theoretically on the simple principle known as “the rectilinear propagation of light”. This function can be calculated from the response functions of each element of the system. In this system the source is of some extent, and the object is interposed between the source and the chamber, casting a blurred shadow on the chamber greater than itself.
The response function of ionization chamber or radiation source is experimentally obtained from the Fourier-transform of the differential of the transient response measured by scanning a shelter plate close to the surface of the subject.
The response functions of cylindrical and spherical chambers with circular, square and rohmbic windows and a radiation source (90Sr) are obtained theoretically and experimentally. These two results are in good agreement.
As to the overall response function, the theoretical values disagree with the experimental values. This must be caused by the effects of scattered β-rays.
The amount and the response function of the scattered rays are remained unknown and left as the next problem to be studied.
