[ 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.

.. code-block:: text
  :caption: **[ Weight Window ]** section example (1)

      [ 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 :numref:`format-tally` 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, :math:`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 :math:`e_{i-1} < E < e_i`.
:math:`e_0 = 0` and :math:`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.