Three-Way And Charged-Particle Coupled Sets

This version of TRANSX is capable of producing transport tables for charged-particle transport and coupled sets for more than two particles. The main difference between charged-particle cross sections and neutral-particle cross sections occurs for elastic scattering, because the Rutherford cross section becomes singular as the scattering angle goes to zero. In practice, this singularity is screened out by the electronic structure of the material. This is no longer a strictly nuclear problem, and the forward transport of charged particles is normally handled as a continuous slowing-down calculation using stopping powers. NJOY constructs charged-particle elastic matrices that include scattering to cosines less than 0.96 only (approximately 20 deg).

Coupled transport is natural for charged-particle problems. High-energy neutrons normally produce secondary protons, and these protons can produce additional secondary neutrons. The structure of a coupled set for neutron-proton-photon transport is shown here. Note that a $(p,n)$ reaction looks like an upscatter event in this type of table. The user must be careful to use NUP>0, and the transport calculation may run more slowly because it will have to use outer iterations.

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