DC gradient-B pumping of tandem-mirror thermal barriers

Passive pumping of tandem-mirror thermal barriers by a combination of E x B and gradient magnetic field (grad-B) drifts has the advantages of engineering simplicity, low power consumption and selectivity in pumping out trapped thermal ions while retaining high-energy sloshing ions, hot electrons, and central-cell ions. Specifically, installing dc perturbation coils in suitable locations utilizes the differences in the turning points of these populations. In addition, we can dispose of the thermalized alphas and impurities after they diffuse into velocity space accessible to the grad-B pumping. Questions concerning adiabaticity are under investigation through guiding-center drift calculations.