Among the different schemes for 14 MeV neutron generators designed for the material testing of the elements of a fusion reactor, the concept of a generator based on a gas dynamic trap has been seriously studied during the last ten years. It is assumed that an oblique injection of fast tritium atoms is used in order to enhance the density of the neutron flux. In this case, a high energy `sloshing' ion component creates a strongly anisotropic plasma pressure with P||>>Pperpendicular to . The effect of anisotropy on the stability of localized ballooning modes and the interrelation of the latter with the `fire-hose' instability are studied on the basis of the paraxial energy principle. In contrast to the standard mirror calculation, the anisotropic model allows a complete analytical treatment of the problem. The fire-hose instability is shown to be of importance for flat radial profiles, while the stability of peaked configurations is restricted by the ballooning modes. In many cases of practical interest, the fire-hose criterion beta ||<or=2 can be used for a rough estimate of marginal stability
Theory and Modelling of Helium Enrichment in Plasma Experiments with Pump Limiters