Radiation, angular distribution diffusion

In addition to thermal desorption, gas desorption has been found to result from electron, ion and photon bombardment of surfaces. Therefore, simultaneous particle and photon bombardments can be expected to alter desorption rates, as well as the nature and charge distribution of the desorbed species. Furthermore, simultaneous bombardment of a surface by neutrons and ions could affect diffusion processes, e.g., by radiation-induced segregation. In turn, desorption processes can be influenced by altering the diffusion of species from the bulk to the surface. The type, energy, and angular distribution of particles expected to strike neutral beam injector dump areas (such areas can represent 1/9 of total first wall area) can cause synergistic effects on gas desorption which can be quite different from those expected from the interaction of plasma radiations with the first wall. 

If the sample is an ideal diffuser, then the angular distribution of the radiation flux through a plane layer dx in a given direction is... 

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