Absolute energy spectra [1/(keV·mAs·sr)] for an industrial micro focal X-ray source has been measured under working conditions, using a Compton scattering spectrometer. The energy spectra were measured as a function of tube potential (30 – 190 kV for every 10th kV) at maximum tube charge of 8 W for the minimum focus (~5 μm diameter). Target material was tungsten. The spectra were measured for a highly focused fresh focal spot. Neither focal spot wear (age) nor defocusing of the focal spot was considered.
The measured spectra were compared to simulated spectra for the same source supplied by the X-ray source manufacturer. It was found that the measured spectra have slightly different energy distributions with a lower mean energy even though their emitted number of photons were similar. The energy calibration was shown to be accurate compared to the energy resolution, Dhu=0.5 keV, used.