The NJOY Nuclear Data Processing System, Volume 1:User's Manual

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TEMPR... Resonances can be constructed directly at an elevated temperature
using the $X resonance shapes (with some loss in accuracy and great savings in
time) for single-level Breit-Wigner or Adler-Adler representations. In general,
it is recommended that resonance reconstruction be performed at zero Kelvin
(TEMPR = O); BROADR can then be used to Doppler-broaden to the desired tempera-
ture with great accuracy.
NDIGIT... All energies are adjusted to have exactly this number of signi-
ficant digits before the cross section is computed, and no two energies are
* allowed to be equal. For formatted output, NDIGIT must be less than or equal to
7; larger values are allowed with binary output, if permitted by the word length
of the computer.
ERRMAX,ERRINT. .. These parameters control an optional resonance-integral
thinning procedure, which helps reduce the number of energy points generated
during resonance reconstruction. The option can be turned off by specifying
ERRMAX = ERR.
c. BROADR Module
ISTART... Since Doppler broadening is comparatively expensive, it is often
useful to “restart” from previous data at a lower temperature. For example, in
attempting to produce cross sections at 300, 900, and 2100 K, the job runs out
of time while doing the last temperature. Set ISTART = 1 and TEMP1 = 900, and
continue the job using the output of the aborted run as input. (If ISTART = O,
none of the input cross sections are copied to the output.)
ISTRAP... “Bootstrap” refers to using the output of one broadening run as
the input for a subsequent higher temperature run. If thinning was used, the
second run can be much faster than the first. However, errors will accumulate.
ERRTHN... Cross sections become smoother with Doppler broadening and can
be thinned. It is recommended that ERRTHN ~ ERR be used. (See Item B above.)
THNMAX. .. Broadening and thinning are not normally performed above 1 MeV
or the inelastic threshold, whichever is lower. In some cases, it is useful to
further reduce this energy, for example to the top of the resolved-resonance
energy range or to an energy that avoids sharp steps or triangular representa-
tions of resonances found for some evaluations (for example, ENDF/B-V lead).
D. HEATR Module
NPK,MTK. .. Usually only the total kerma is needed (NPK = O). For struc-
tural metals, MTK = 444 can be requested to obtain the total radiation damage
production cross section. Other partials are useful in connection with IPRINT=
2.
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