THE EGS5 CODE SYSTEM

Following is the output produced by tutor4.f, showing that the severe step-size dependence exhibited
by EGS4 on this problem is greatly diminished in EGS5. Recall that in the tutor4 example
of EGS4, runs using the default step-size algorithm predicted 1.3% reflection and 49.21.0%, EGS4
returned values of 6.4% reflection and 61.3% transmission. In contrast, an EGS5 run using very
long multiple scattering steps (corresponding to 30% energy loss over the steps, and labeled “loop
1” in the output file) yields values for reflection (8.1%) and transmission (66.5%) which are fairly
close to EGS5 results generated with 1% energy loss steps (7.3% and 64.4% for reflection and
transmission, respectively, “loop 2” in the output). This level of agreement (roughly 3% error in
the transmission fraction, even when using 30illustrates the power of the modified random hinge
approach. In addition, the significant discrepancies between the 1% energy loss step results of
EGS4 and EGS5 forcefully demonstrate the shortcomings of the EGS4 transport mechanics model,
even for very small electron step sizes.
The results from the third part of this example (“loop 3”) show that the expected 1% accuracy
is obtained when the multiple scattering steps sizes are chosen automatically by EGS5 based on
the given characteristic dimension of 2 mm for this problem. Note that for this dimension and at
this energy, the step-sizes selected by EGS5 for silicon are roughly 10-15 times as large as those
used in the 1% energy loss run (loop 2), thus providing significant speedup (a factor of three, as
seen from the output) for calculations at this level of accuracy.
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Initializing EGS5, loop = 1: charD = 0.00
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PEGS5-call comes next
Using media number 1, SI with long steps
for this run
inseed= 1 (seed for generating unique sequences of Ranlux)
ranlux luxury level set by rluxgo : 1 p= 48
ranlux initialized by rluxgo from seed 1
Start tutor4
Call hatch to get cross-section data
HATCH-call comes next
EGS SUCCESSFULLY ’HATCHED’ FOR 2 MEDIA.
WARNING in RMSFIT: no characteristic dimension input for media 1
Using old data from gsdist.dat with:
efrach, efrachl = 3.0000E-01 3.0000E-01
WARNING in RMSFIT: no characteristic dimension input for media 2
Using old data from gsdist.dat with:
efrach, efrachl = 1.0000E-02 1.0000E-02
Knock-on electrons can be created and any electron followed down to
0.189 MeV kinetic energy
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