A mechanism for ion acceleration near the anode of a magnetically insulated ion diode

We propose a theoretical model for the ion acceleration near the anode in the anode plasma of a magnetically insulated ion diode (MID). The applied diode voltage is screened by the anode plasma. We assume that as a result of the strong magnetization of the electrons and nonmagnetization of the ions in the anode plasma, a narrow space charge sheath is formed near the anode, of a width close to the electron Larmor radius. The potential drop that is formed across the sheath accelerates the ions born inside the sheath into the plasma. We solve a system of equations for the sheath and derive an approximate expression for the potential drop across the sheath. This expression exhibits the dependence of the ion energy on the magnetic field intensity and on the electron temperature and density. We also discuss an influence of the sheath width to the electron Larmor radius ratio as a parameter. The theoretical results are found to be in good agreement with the experimental measurements.