[ Identification | Description | Input parameters | Links ]
MCViNE_Phonon_IncoherentElastic ComponentIsotropic incoherent elastic scattering damped by the Debye-Waller factor. dw_core [AA^2] is given directly, or (dw_core<0) computed from a phonon DOS, temperature and average atomic mass exactly as MCViNE's DWFromDOS. McStas' Incoherent has no Debye-Waller factor. Transport (same as MCViNE HomogeneousNeutronScatterer): on the first passage the neutron is forced to scatter at a uniformly chosen depth, weighted by path length, attenuation exp(-(mu+sigma)x) and the scattering coefficient; on exit it is attenuated by exp(-(mu+sigma)L_out). With order>1 further scatterings are sampled analogically (truncated exponential). With p_transmit>0 that fraction of events is kept as the attenuated direct beam. mu(v) = absorption_coefficient*2200/v. Events for which the kernel cannot scatter (kinematically forbidden) are absorbed. Geometry: box (xwidth,yheight,zdepth), cylinder (radius,yheight), hollow cylinder (+thickness) or sphere (radius only). All vectors (Q, targets, reciprocal vectors, atom positions) are in the component's local frame. Uses the shared runtime share/mcvine-lib.h/.c. Example: MCViNE_Phonon_IncoherentElastic(dw_core=0.0067, sigma_inc=10, sigma_abs=10, Vc=27.6, radius=0.01, yheight=0.05)
| Name | Unit | Description | Default | |
| dw_core | AA^2 | Debye-Waller core u^2 (2W = dw_core*Q^2); <0: compute from dos | -1 | |
| dos | str | Phonon DOS file (2-column E[meV] g, or MCViNE IDF DOS) for dw_core<0 | 0 | |
| T | K | Temperature (for dw_core from DOS) | 300 | |
| average_mass | amu | Average atomic mass (for dw_core from DOS) | 0 | |
| sigma_inc | barn | Incoherent scattering cross section per unit cell | 0 | |
| sigma_abs | barn | Absorption cross section per unit cell at 2200 m/s | 0 | |
| Vc | AA^3 | Unit cell volume | 0 | |
| radius | m | Outer radius of a cylinder (with yheight) or of a sphere (yheight=0) | 0 | |
| xwidth | m | Width of a box sample | 0 | |
| yheight | m | Height of a box or cylinder sample | 0 | |
| zdepth | m | Depth of a box sample | 0 | |
| thickness | m | Wall thickness of a hollow cylinder (0: filled) | 0 | |
| pack | 1 | Packing factor (scales absorption and scattering coefficients) | 1 | |
| p_transmit | 1 | Monte Carlo fraction of events kept as unscattered transmitted beam (0: always scatter) | 0 | |
| order | 1 | Maximum number of scattering events per neutron (1: single scattering) | 1 |
| AT ( | , | , | ) RELATIVE | |||
|---|---|---|---|---|---|---|
| ROTATED ( | , | , | ) RELATIVE |
MCViNE_Phonon_IncoherentElastic.comp.
[ Identification | Description | Examples | Input parameters | Links ]
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