Figure 3

Left: Ideal case with the absence of time delay. The blackening of the film on the bottom has the exact length of the desired irradiation. Right: Real case with system latency: There is a difference in exposure length between the BEAM-ON signal and the actual exposure of the film (ΔL _BEAM-ON ) and a difference between the termination signal of the linac and the actual termination of the beam (ΔL _BEAM-OFF ). Both of these can be measured and with a given velocity, the time delay of the system (Δt _BEAM-ON and Δt _BEAM-OFF ) can therefore be calculated. The schematic blackening of the film on the bottom of each subfigure is a transposition of the film onto the time axis, as ΔL behaves linear proportional to the time delay Δt for given velocities.