Off-axis x-ray spectra: A comparison of Monte Carlo simulated and computed x-ray spectra with measured spectra

The off-axis x-ray spectra from a constant potential x-ray generator were measured with a high purity germanium spectrometer cooled to liquid nitrogen temperature. The measured spectra were compared with off-axis x-ray spectra calculated using a code based on the semiempirical model developed by Tucker et nl, and Monte Carlo simulated x-ray spectra using the EGS4 code system. In this study, both the Tucker model, and the EGS4 code system, were found to produce off-axis bremsstrahlung x-ray spectra which agreed well with the spectra measured at three emerging angles. In the measured and the EGS4 generated spectra the total K-characteristic peaks were in increasing order, as observed in the anode to cathode direction, whereas the Tucker model produced maximum total K-characteristic peaks at the 6 degrees anode side, and lesser amounts at the central axis and the 6 degrees cathode side. Large differences in the total K-characteristic lines is seen among the three different methods. The EGS4 code system was able to produce x-ray spectra for a combination of target materials. (C) 1999 American Association of Physicists in Medicine. [S0094-2405(99)02102-1].