Neoclassical transport and alpha particle confinement in novel 3-D reactor systems

Neoclassical transport and a particle confinement are analysed for three 3-D reactor designs-the QAS3, the ST/sphellamak hybrid and the sphellamak-using the VENUS code. It is observed that neither the QAS3 nor the ST/sphellamak is truly aquasi-axisymmetric configuration. Thus the transport is governed by the helical deformation of the magnetic Field strength, and these configurations do not effectively confine the trapped a particles. On the other hand, the sphellamak is a nearly isodynamic structure in the plasma core, which leads to almost perfect a confinement, and the neoclassical transport is very similar to that obtained in a 2-D equivalent tokamak.