Role of end regions in the steady state of mirror-confined plasmas

In open-ended plasma confinement at reasonable ion temperatures and relatively high densities (such as 10 keV and 1013 cm-3, or 100 eV and 1010 cm-3) the Coulomb-scattering loss flux alone gives rise to a charged-particle density outside the mirrors that is usually large enough to require quasi-neutrality there. Such confinement must therefore be considered as involving an external plasma even in the absence of ionization or other plasma sources in this external region. The authors have investigated some of the effects of this plasma on the steady-state features of mirror confinement. In particular, they find that a significant electrostatic potential must usually exist between a mirror and any external boundary (though its magnitude can be reduced by plasma sources outside the mirrors). It follows that some energetic electrons will have turning points well outside the mirrors and yet remain trapped.