Key points are not available for this paper at this time.
A geometric-progression (G-P) method formula, Br = 1 + (B − 1) · (Kx − 1)/(K − 1), accurately represents the buildup factor data as a function of distance for the following reasons:1. The value of parameter B corresponds to that of the buildup factor at 1 mfp, which is the integration of a basic spectrum for a specified material and for a specified source energy.2. The variation of parameter K with penetration represents the photon dose multiplication and the change in the shape of the spectrum.Exposure buildup factors for point isotropic sources in an infinite medium approximated by the G-P fitting parameters are in good agreement with the basic data calculated by the PALLAS code, including that of boron for low energies, and of lead, including the effects of bremsstrahlung and fluorescence.The validity of using the G-P parameters to interpolate the buildup factor in μr and in E is ascertained. Furthermore, the extrapolation to the buildup data for depths above 40 mfp is examined.
Harima et al. (1986) studied this question.