A d-d Tandem Mirror Reactor with Central-Cell Potential Modification

Abstract

A conceptual tandem-mirror reactor (TMR) configuration consists of a solenoidal central-cell with its ends plugged by a combination of electrostatic and magnetic fields. The magnetic fields in the end plug also provide MHD stability. The electrostatic plugs for ions and electrons are created by combining hot electron plasmas and neutral beams for fueling and pumping. A large negative potential may be formed in the end plug to contain central cell electrons, but the central cell floating potential /phi/ /SUB f/ is driven negative as charge neutrality is maintained. Cat-d TMR plasma performance is assessed with respect to standard (positive), neutral and negative central cell potential operating modes. It is determined that the plasma Q for a 2000 MW fusion power reactor is peaked for central cell potential /phi/ /SUB f/ near zero. This is because on one hand, the ion-loss cone is bigger for positive /phi/ /SUB f/ and the ion plug electrons must overcome larger /phi/ /SUB f/ + /phi/ /SUB c/ and hence more ECH is required to build the ion plug, and, on the other hand, the electron loss-cone is bigger for negative /phi/ /SUB f/ and synchrotron losses are severe. A zero-dimensional plasma physics model formore » the density and power balance of a Cat-d TMR has been developed from an existing code that models a d-t TMR operating with a positive central cell potential. The new Cat-d code models all potential operating modes and has been benchmarked.« less