Hello, I've simulated the output of a x-ray tube using a software (spekcalc). In my simulation the energy range is 17-170 keV, the air thickness is 1m and there is 1.5 mm of Al. The mA value is 1 (default value). After the estimation I obtained a characteristic spectra: in y there is the numper of photons [keV cm^2 mAs^-1 @ 1 meter] while in x there are the energy range (17-170 keV). The mean energy = 61 keV, bremsstrahlung = 273 μGy/mAs @1 meter and characteristic energy = 26 μGy/mAs @1 meter. I know how to estimate the mean energy using the spectra data, but I don't know how the bremsst and the characteristic energy is estimated. Any help? Moreover, I'd like to know the values at 1.5m of air, so I wanted to use the inverse square law(I1/I2=D1^2/D2^2, where I1 and I2 are the intensity values at D1 and D2 respectively)..can I apply this to bremmst and characteristic energy? Thanks!