On the plug potential formation mechanism in a tandem mirror.

A formation mechanism of the plug potential in a tandem mirror is proposed. The orbits for ions, which are accelerated by the thermal barrier potential, are calculated numerically in a magnetic mirror field. A non-Maxwellian electron distribution function, which leads to a modified Boltzmann law, is assumed in order to determine the electrostatic potential profile. Monte Carlo simulation is carried out for ion dynamics to include the effects of Coulomb collisions and ion radial losses. It is found that the plug potential is formed under the condition that the ions trapped in the thermal barrier region are few. [ABSTRACT FROM AUTHOR]