Figure A3.

The 6MV FFF treatment beam source spectrum (used for the MC simulations) and source photons per energy bin (analytical simulations) are shown. To reduce the computational time and memory requirements, non-uniform source photon energy bins ( $N_0^j$) were used (solid dots, right axis). When divided by the energy bin width (photons/bin → photons/MeV), the analytical source photon distribution spectrum matches the desired 6 MV FFF spectrum. The energy bin centered at 2.1 MeV has a larger width—and amplitude—than the surrounding bins.