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The keys to finding your way around on an ENDF tape are
the MAT, MF, and MT numbers. On the ASCII versions of
ENDF-format files, they appear in columns 67 to 75 of
every "card" (we also use the term "card" out of respect
for the history of computing--besides, some of us
remember them real well!). The Fortran notation is
I4,I2,I3. The MT value is zero to indicate the end of a
section (SEND record), the MF value is zero to indicate
the end of a file (FEND record), and the MAT number is zero
to indicate the end of a material (MEND record). There is
a special "tape ID" record at the beginning with the MAT
value equal to the tape number, and a special tape-end
record (TEND) with MAT=-1 at the end of the tape.
Here is an example of the skeletal structure for a typical
ENDF tape (the 5-digit sequence numbers in columns 76 to
80 have been omitted for clarity):
tape id 7777 0 0
start of MF1, MT451 (description) 1111 1451
...
SEND record 1111 1 0
FEND record 1111 0 0
start of MF2, MT151 (resonances) 1111 2151
...
SEND record 1111 2 0
FEND record 1111 0 0
start of MF3, MT1 (total cross section) 1111 3 1
...
SEND record 1111 3 0
start of MF3, MT2 (elastic cross section) 1111 3 2
...
FEND record 1111 0 0
MEND record 0 0 0
TEND record -1 0 0
To find samples of this kind of structure, look at the
"raw" ENDF files from
ENDF/B-VII,
JEF-3.0, or
JENDL-3.3.
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