[ Identification | Description | Input parameters | Links ]
MCViNE_ConstantvQE_process Componentkf = ki - Q (Q vector fixed in the sample frame); the event weight is multiplied by exp(-(E-E0)^2/(2 dE^2)) where E = Ei-Ef. Used for single-crystal resolution studies. Union process. Part of the Union components: define this process, collect it into a material with Union_make_material (absorption is set there with my_absorption, the absorption inverse penetration depth at 2200 m/s), assign the material to Union_box/Union_cylinder/Union_sphere/Union_mesh geometries, and add a Union_master after them. Geometry, attenuation and multiple scattering are handled by Union_master; this component provides the MCViNE kernel: the scattering coefficient and the final-state sampling (weight). Orientation: this process is anisotropic; its frame (Q vectors, reciprocal vectors, atom positions) follows the ROTATED placement of this component. The kernel code is shared with the standalone component MCViNE_ConstantvQE (mcvine-lib.c). Uses share/mcvine-lib.h/.c and share/mcvine-union-lib.h/.c; the process type MCViNE is declared in share/union-lib.h and registered with Union_master in share/mcvine-union-lib.h. Example: MCViNE_ConstantvQE_process(Qx=1, Qy=0, Qz=0.5, E=10, dE=1, scattering_coefficient=10)
| Name | Unit | Description | Default | |
| Qx | AA^-1 | Q vector x | 0 | |
| Qy | AA^-1 | Q vector y | 0 | |
| Qz | AA^-1 | Q vector z | 0 | |
| E | meV | Nominal energy transfer | 0 | |
| dE | meV | Gaussian sigma of the energy weight | 1 | |
| scattering_coefficient | m^-1 | Scattering coefficient (inverse penetration depth for scattering) | 0 | |
| sigma_scat | barn | Alternative: scattering cross section per unit cell (used when Vc>0) | 0 | |
| Vc | AA^3 | Unit cell volume; when >0 the coefficient is sigma_scat/Vc | 0 | |
| packing_factor | 1 | Packing factor (scales the scattering coefficient) | 1 | |
| interact_fraction | 1 | Union: fraction of interactions forced to this process (-1: by cross section) | -1 | |
| init | string | Deprecated and unused, accepted like on the other Union components (see Union_init). | "" |
| AT ( | , | , | ) RELATIVE | |||
|---|---|---|---|---|---|---|
| ROTATED ( | , | , | ) RELATIVE |
MCViNE_ConstantvQE_process.comp.
[ Identification | Description | Examples | Input parameters | Links ]
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