Confinement of a mirror plasma with an anisotropic electron distribution function

Abstract

A theoretical model has been developed for an electron-cyclotron-resonance-heated plasma confinement in a mirror magnetic trap. The model is based on the simultaneous study of noncollisional kinetics of electrons and gas dynamics of ions. At the trap center, the electron velocity distribution function is approximated by bi-Maxwell distribution with two effective temperatures, transverse and longitudinal to the magnetic field. Electrons were assumed to be hotter than ions. Axial distributions of the ambipolar potential and plasma density as well as the ion confinement time have been investigated both numerically and analytically. A simple formula for the lifetime is suggested. Numerical simulations as well as the formula show that the confinement time is heavily dependent on the electron distribution anisotropy and, in the strongly anisotropic case, on ion temperature if the latter is not too small. With increasing anisotropy the ambipolar potential changes qualitatively, acquiring a peak between the trap center and the plug.© 1998 The American Physical Society.