Fig. 1From: PENELOPE/PRIMO-calculated photon and electron spectra from clinical acceleratorsCalculated photon spectra (planar fluence differential in energy) for 6, 10, 15 and 20 MV Varian clinical beams normalized to their integral. The dashed histograms correspond to spectra for 6 and 10 MV FFF beams. Observe the 511 keV peak resulting from positron annihilation, visible in the higher energy beamsBack to article page