Abstract
Energy spectra of primary X-rays emitted from an X-ray tube under different radiographic conditions provide useful informations in radiology such as, basic practical data for calculation in radiation protection or for reduction of diagnostic exposures to man. We are currently attempting by correlation between the primary X-ray spectra and those of the secondary X-rays passing through the phantom, to obtain the X-ray images containing the most possible informations at the least exposures. As the first step in such an attempt, we make a study to establish the method of measuring the primary X-ray spectra with lithium-drifted dilicon detector.