defines the energy limits for a Russian Roulette/splitting weight
window and applies particle-dependent modification factors to the
windows defined by WW-FACTOr
(see also BIASING, WW-FACTOr, WW-PROFIle)
WHAT(1) > 0.0: upper kinetic energy threshold in GeV for RR/Splitting
with a weight window. For low-energy neutrons,
corresponding (smallest) group number (included).
= 0.0: ignored
< 0.0: any previously selected threshold is cancelled
WHAT(2) >= 0.0 and < WHAT(1): lower kinetic energy threshold in GeV
for RR/Splitting with a weight window. For low-energy
neutrons, corresponding (largest) group number
(included)
< 0.0 or > WHAT(1): WHAT(2) is set = WHAT(1)WHAT(3) > 0.0: amplification factor used to define the weight window
width at the higher energy threshold represented by WHAT(1).
The weight window at the higher energy threshold is
obtained by multiplying by WHAT(3) the top edge of the
window (splitting level) at the lower threshold, and
dividing by the same factor the bottom edge
(RR-level).
< 0.0: |WHAT(3)| is used as multiplication factor for the
bottom and top levels of every region for the particles
selected by WHAT(4-6). That is, for such particle(s) both
bottom and top levels are multiplied by |WHAT(3)|
Default = 10.0 (amplification factor for the splitting and RR-level
at the higher threshold). The particle dependent
multiplication factor by default is set = 1.0.
WHAT(4) = lower bound of the particle numbers to which the indicated
weight window energy limits apply
Note that particle number 40 indicates low-energy neutrons
(for this purpose only!). Particle number 8 indicates neutrons
with energy > 19.6 MeV.
("From particle WHAT(4)...").
Default = 1.0.
WHAT(5) = upper bound of the particle numbers to which the indicated
weight window energy limits apply
("...to particle WHAT(5)...").
Default = WHAT(4) if WHAT(4) > 0, all particles otherwise.
WHAT(6) = step length in assigning numbers. ("...in steps of
WHAT(6)").
Default = 1.0.
SDUM = PRIMARY: the weight window applies also to primary
particles (default)
= NOPRIMARy: the weight window doesn't apply to primaries
Default (option WW-THRESh or WW-FACTOr not given): no weight window is
defined
Note: this option is only meaningful when WW-FACTOr is also
requested. See the note to that option for more information.
For low-energy neutrons, the two energy thresholds are expressed
as group numbers, while for all other particles (including
high energy neutrons) they are expressed in GeV. Therefore,
thresholds for low-energy neutrons must be assigned in a
separate WW-THRESh card from other particles.
Example:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7...+...8
WW-THRESh 2.0 0.05 2.4 3.0 7.0 0.0
* The weight window weight limits for particles 3 to 7 (practically electrons,
* positrons and photons, since neutrinos are discarded), which have been set
* by WW-FACTOr are applied as such below 50 MeV. Above that energy, the width
* of the window is progressively increased up to 2 GeV: at 2 GeV, the upper
* weight limit is a factor 2.4 larger and the lower limit a factor 2.4
* smaller.
