Measurement and validation of benchmark-quality thick-target tungsten X-ray spectra below 150 kVp

Pulse-height distributions of two constant potential X-ray tubes with fixed anode tungsten targets were measured and unfolded. The measurements employ ed quantitative alignment of the beam, the use of two different semiconduct or detectors (high-purity germanium and cadmium-zinc-telluride), two differ ent ion chamber systems with beam-specific calibration factors, and various filter and tube potential combinations, Monte Carlo response matrices were generated for each detector for unfolding the pulse-height distributions i nto spectra incident on the detectors, These response matrices were validat ed for the low error bars assigned to the data. A significant aspect of the validation of spectra, and a detailed characterization of the X-ray tubes, involved measuring filtered and unfiltered beams at multiple tube potentia ls (30-150 kVp), Full corrections to ion chamber readings were employed to convert normalized fluence spectra into absolute fluence spectra, The chara cterization of fixed anode pitting and its dominance over exit window plati ng and/or detector dead layer was determined. An Appendix of tabulated benc hmark spectra with assigned error ranges was developed for future reference . (C) 2000 by Radiation Research Society.