A bounce-averaged ion Fokker-Planck code for Penning fusion devices

A bounce-averaged Fokker-Planck code (BAFP) has been developed and tested. BAFP implements a multi-dimensional, energy-conservative, time-implicit sol ution of the Fokker-Planck equation in two velocity and one spatial dimensi ons. A Jacobian-free, Newton-Krylov solver efficiently inverts the time-imp licit equations. Bounce averaging removes the fast time scale for motion of trapped ions, so low-collisionality ion systems can effectively be treated . BAFP has been applied to ion dynamics in virtual-cathode spherical inerti al electrostatic (IEC) fusion devices, which employ a spherical cloud of el ectrons to create a kV electrostatic well to confine and spherically focus ions. Here, Penning-type IEC devices are studied. Steady-state ion distribu tion functions obtained with BAFP in operating limits of interest are prese nted, and show that a variety of steady-state equilibriums are possible in these systems. (C) 2001 Elsevier Science B.V. All rights reserved.