Abstract
The voltage-ripple dependence relations on x-ray spectra and mean energies at 70 kVpeak were obtained theoretically by using the semi-empirical formula of emission spectra given by Birch and Marshall (1979). The calculations were carried out for objects of various thicknesses of acrylic resin and aluminium, and also without an object. As the ripple increases, the spectral componeuns generally move to the low photon-energy side. But with the ripple at 40-60%, the spectral components return slightly to the high photon-energy side in both the saturating and unaturating current modes. Therefore the mean energy reaches the minimum value at 40-60%ripple. This phenomenon was pointed out by Birch et al (1979) only for the saturating current modes. We found this phenomenon also for the unaturating current mode. We verified this phenomenon experimentally for the saturating mode. The reasons for this phenomenon were clarified.
