Collisional limits of resonant and neoclassical transport in tandem mirrors

Neoclassical and resonant transport in tandem mirrors in considered in the limit where the collision frequency nusub(c) exceeds the bounce frequency nusub(b) for solenoid ions. Approximate expressions for the diffusion coefficient are obtained analytically and verified by using a random walk code. These expression scale as nusub(c), (nusub(c)/nusub(d))sup(1/2)nusub(b), or nusub(b), depending on the value of the azimuthal drift frequency nusub(d). The connection to regimes of lower collisionality is described. In particular, for neoclassical transport (nusub(d)/nusub(b)<<1) at moderate collisionality, a mechanism previously described but not generally known leads to a term in the diffusion coefficient which scales as nusub(c) and allows smooth matching to the high-collisionality regime. (author)