Enhancement of ponderomotive end plugs with low-mass dopants

During conventional confinement of a linear plasma using ponderomotive end plugs, a repulsive potential is created at the axial ends by employing a perpendicularly polarized wave with a wave frequency greater than the ion gyrofrequency. This potential is then partially canceled out by an ambipolar potential that arises to equilibrate electron and ion densities along the field line. However, recent work on centrifugally confined plasmas has shown that the appropriate choice of a dopant in the end region can dramatically change the structure of the ambipolar potential. For the ponderomotive potential, this ambipolar shaping can be even more powerful, since a lightweight dopant can see a different sign of ponderomotive potential relative to the confined species. As a result, the dopant can reverse the sign of the ambipolar potential, causing it to dramatically enhance the end plug ponderomotive confinement.