5.19. [ Weight Window ] section¶
The weight window function can be defined in this section. A maximum of 6 [weight window] sections can be defined in an input file.
[ Weight Window ]
mesh = reg
part = proton neutron
eng = 5
( tim = 5 )
6.00e-7 3.98e-1 1.00e+0 7.00e+0 5.00e+4
reg ww1 ww2 ww3
1 0.010000 0.100000 0.001000
11 0.005000 0.050000 0.000300
( { 2 - 5 } 8 9 ) 0.001000 0.010000 0.000100
( 11 12 15 ) 0.000500 0.005000 0.000030
( 6<10[1 0 0]<u=3 ) 0.000010 0.001000 0.000010
.... ........ ........ ........
ww4 ww5
0.010000 0.100000
0.005000 0.050000
0.001000 0.010000
0.000500 0.005000
0.000010 0.001000
........ ........
Mesh type should be defined in the first line, that is, mesh=reg, mesh=xyz, or mesh=tet. When mesh is not defined, the default setting mesh=reg is used. For mesh=xyz, x-type, y-type, and z-type must be defined in subsequent lines. Please see Section 6 for details. Note that surfaces of the xyz mesh should be slightly shifted from cell surfaces. Please be especially careful if you are using parameters to link geometry boundaries and xyz mesh ranges. After version 3.34, if the maximum and minimum xyz mesh values for [weight window] and [t-wwg] are defined as integers, the minimum value is shifted by -1*deltxyz and the maximum value by +2*deltxyz from the integer. The mesh option mesh=tet can be used only for geometries containing tetrahedral-mesh geometry. The cell number specification of the rectangular box where the tetrahedral-mesh geometry is implemented needs to be followed as reg=. The weight window for each tetrahedron element can then be specified.
Particle type should be defined as part=. part=all means all particles. The format used in part= is the same as that in tally definitions. However, it can distinguish only ityp, and each nucleus is not specified individually.
Next, you define the energy mesh or time mesh. First, define the number of meshes by eng= or tim=. In the next line, define the values of each mesh, \(e_1, e_2, e_3, ...\). Minimum values of the weight window for each mesh should be defined in the following lines. Each minimum value is written as ww1, ww2, ww3, and so on. Here, wwi is the minimum value of the weight window for a mesh \(e_{i-1} < E < e_i\). \(e_0 = 0\) and \(t_0 = -\infty\) are assumed. If there are no eng= or tim= definitions, energy or time meshes are not prepared. In this case, you should set only ww1.
Region information, reg, xyz, or tet, must be written in the first column. As shown in the example above, you can make another table for wwi definitions. From the second table onward, the region definition can be skipped. You can use the skip operator non in this section.
For mesh=reg, you can use the format ( { 2 - 5 } 8 9 ), and you can use the lattice and universe style ( 6 < 10[1 0 0] < u=3 ). However, a value must be enclosed by ( ) if it is not a single numeric value. For mesh=xyz, the position of each data should be defined as (ix iy iz). For mesh=tet, minimum values of the weight window for all tetrahedron elements need to be specified following the element number.
For highly penetrating particles, such as neutrinos, assigning a large importance may lead to a significant increase in computation time. To avoid this issue, neutrinos are excluded even when part=all is specified; please take note of this behavior.