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The data-flow example on the previous page introduces the terms
"PENDF tape" and "GENDF tape." Because these files will be
very important for all the NJOY examples, we define them more
completely here:
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PENDF tape: a pointwise version of an ENDF tape
where any resonance parameters or nonlinear interpolation
ranges have been converted into pointwise cross sections
suitable for linear interpolation to within specified
accuracy criteria. The File 1 comments have been simplified,
although the directory is correct. Resonance parameters have
been removed from File 2. Only Files 3, 6 (for thermal data
only), and 13 are given for data; the other information, such
as angle and energy distributions, must be read from the
corresponding ENDF tape. Multiple temperatures may be given
for a material by repeating each "MAT" in order of increasing
temperature.
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GENDF tape: a multigroup version of an ENDF tape with
the group structures, temperatures, and background cross
section defined in File 1, "vector" cross sections given
in File 3, and group-to-group matrices given in File 6.
Higher MF Files are used for photons and charged particles.
Using these standardized files supports the modular nature of
NJOY. Different modules can sometimes be run in different
orders and combined in various ways. Internally, all NJOY
modules use a common set of subroutines for reading and writing
the ENDF, PENDF, and GENDF "tapes" (they are located in the NJOY
module).
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