- The idea is to define a current surface detector which track particles crossing in/out the surface - regardless whether the particle interacts inside the surface, and limit the spatial domain of integration of the surface by adding a collision detector (of type cell or mesh - super-imposed). The surface detector estimates are integrated over the “reduced” surface, energy and all directions - by “reduced” I mean region define by the original surface with boundaries defined by the mesh and/or cell detector.

- Collision detectors, e.g. mesh detectors are volumetric in 3D geometries. Meaning, its definition should involved a real volume. Setting in a curvilinear detector an equal minimum and maximum radius would not define a zero volume (theoretically that corresponds with a line).

- I will try to exemplify this capability:

Code: Select all

```
surf 100 cube 0 0 0 50
surf 200 cube 0 0 0 100
surf 300 py 50
surf 400 py 25
cell 50 0 material_1 -100
cell 60 0 material_2 100 -200
cell 70 0 outside -200
det 1 ds 100 1
det 2 ds 300 1
det 3 ds 100 1 dx -25 25 1
det 4 ds 300 1 dx -25 25 1
det 5 ds 300 1 dx -25 25 1 dz -25 25 1
det 6 ds 400 1 dc 50
```

Note that dx -25 25 1 Cartesian detector defines a volume: x in [-25,25] y in [-INFTY, INFTY], z in [-INFTY, INFTY] - y and z ultimately defined by the 3D (model) geometry boundaries. As well, dc 50 cell detector defines a volume: within surface 100, x in [-50 50], y in [-50 50] and z in [-50 50].

Results are integrated over space, energy and all directions (particles/s). Keep in mind that the integration domain has been re-defined when normalise by the detector area.