A flow chart showing the steps taken to simulate the linac is given. The gray lines represent electron phase space outputs, the black line represents the final dose distribution output, and all the simulation programs used are given in italics. The relevant sections describing each step are also shown in the flow chart.
(a) The electron gun current with the ordinate axis converted to current using the pulsed transformer’s conversion of 1.0 A/V. The dotted line reflects the current value measured on the electron gun and represents . (b) The potential drop at the cathode during the radiation pulse with the ordinate axis reflecting the correction factor required due to the oscilloscope impedance. The dotted line represents the potential used for the electron gun simulations and represents . (c) The target current of measured from a Varian 600C is shown with the ordinate axis changed to current using Ohm’s law.
The electron gun design is shown in the plane. All dimensions are in mm.
The transverse phase space from EGN2W. The effect of spherical aberrations and nonlinear electric fields causes the nonlaminar aspect of the EGN2W electron beam.
The and normalized spatial intensity distribution profiles at the target are given.
Measured and simulated inline and crossline profiles for the 0.25 mm cavity shift at 1.5, 5, 10, and 20 cm depths.
The crossline dose profiles for three different mean total energies of 5.4, 5.6, and 5.8 MeV were compared to measurement to determine the correct beam energy. Only this section of the profile is shown for visual clarity. The left half of this profile as well as the inline profile is identical to what’s given above.
The optimal electron beam total energy spectrum for an inline side-coupled 6 MV linac waveguide. The two large energy peaks correspond to total energies of 5.8 and 6.3 MeV with the spectrum’s maximum and mean total energy of 6.3 and 5.6 MeV, respectively.
(a) Crossline profiles for , , , and field sizes at 5 cm depth. (b) Inline profiles for the same field sizes at a depth of 10 cm. The profiles were initially normalized to the CAX dose and then were scaled in the plots for visual clarity.
The DD curves for the , , , and field sizes were initially normalized at and were then scaled for visual clarity. The uppermost DD curve is for the field and the bottommost DD curve is for the field size with the and curves falling in between.
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