THE EGS5 CODE SYSTEM

tranport step 1
DEINITIAL1 DERESID1
transport step 2
DEINITIAL2
DERESID2
translation step,
DERESID1 + DEINITIAL2
A.) Escape prior to end
of transport step
previous energy hinge
Boundary
A.) Energy decremented at last hinge,
but not yet deposited in translation
A.) DENSTEP
next energy hinge
B.) Energy deposited in
translation, but not yet
decremented
Energy deposition
Boundary
B.) DENSTEP
B.) Escape after end of
transport step
Figure 2.14: Electron boundary crossing during translation steps. In the top schematic (case A),
the electron crosses escapes the problem volume before traversing the full distance corresponding
to the initial transport step (i.e., through both legs of the hinge), while in the bottom schematic
(case B), the particle escapes the volume after the completion of initial transport step. In case A,
the full transport step CSDA energy loss is decremented from the particle’s energy at the time it
passes through the hinge point, but as the particle has not traveled the distance corresponding to
that amount of energy loss, some kinetic energy must be added back to the particle. In case B,
the particle crosses the boundary during the first leg of the second energy hinge step, thus it has
deposited energy into the system even though its energy has not been updated, so some kinetic
energy must be subtracted at that point. In either instance, the final energy of the electron can be
shown to be E = E − DEINITIAL + DENSTEP.
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