Although semi-empirical models exist to calculate the x-ray emission
for electron-collision targets ( e.g.,\
Pella[2]), we have used
simple but fundamental models to represent the
microphysics of electron transport and x-ray production within the target.
This approach allows us to model the target without macroscopic parameters
derived from previous measurements of electron-impact x-ray spectra
(such as line--to--continuum ratios) that must
be included in semi-empirical models. For example,
Pella et al.
[2] compiled parameters to determine only the 
,
, 
and 
lines, using x-ray data from
targets with 
. Determining the intensities of
other lines requires additional data, and extrapolation of model parameters
to atomic numbers outside
of the Cr - W region may be problematic. In our approach, we specify the
problem at a more fundamental level, using parameters that determine electron energy loss,
ionization cross sections, x-ray radiative transition probablitites, and
mass attenuation coefficients. Such an approach also makes
simulating multilayer or compound targets a straightforward extension to
simulating a monolithic target.