THE EGS5 CODE SYSTEM

One of these six cross sections is selected by the user by specifying a PEGS5 input parameter. EII
is treated as being a part of Møller scattering in the EGS5 code, and neither the electron mean-free
path nor the stopping power are modified by including EII.
After a K-shell vacancy creation by EII, the emission of a K x-ray is sampled using the K-
shell fluorescence yield. This is identical to the calculation after a K-shell vacancy creation by the
photoelectric effect, although no Auger electron or cascade particle is followed in the treatment of
EII. For the case of K x-ray emission, the K x-ray energy is sampled from the ten K x-ray energies
listed in [57] according to the relative yield of the K x-ray, and the difference between E B (K shell
binding energy) and the K x-ray energy is deposited locally. In the case that no K x-ray is generated
(i.e., Auger electron emission), E B is deposited locally.
1.4.3 Other Improvements
Merging of EGS and PEGS
Historically, EGS, the simulation code, and PEGS, the data generation code, were completely
separate entities. This left open the possibility that a simulation could work on inappropriate
data, despite the built-in integrity checks. In EGS5, the two codes have been merged, and now
EGS calls PEGS during its initialization procedures. Since the elastic scattering runtime databases
can require large amounts of CPU time in certain cases, the capability to reuse PEGS data files
still exists, but its use is discouraged unless the accurate low energy elastic scattering option is
employed.
Long sequence random number generators
EGS5 employs the RANLUX random number generator[82], with the default “luxury level” set to
one. RANLUX has a period of 10 155 unique random numbers and at luxury level 1 has a fidelity
approximately equal to that of RANMAR[81], which became the default random number generator for
EGS4 in the interim period between major releases. The user may override the default luxury level
and so employ sequences which pass more stringent tests of randomness, although at a significant
cost in speed.
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