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 nonmagnet ization 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 radi us. The potential drop that is formed across the sheath accelerates th e ions born inside the sheath into the plasma. We solve a system of eq uations for the sheath and derive an approximate expression for the po tential drop across the sheath. This expression exhibits the dependenc e of the ion energy on the magnetic field intensity and on the electro n temperature and density. We also discuss an influence of the sheath width to the electron Larmor radius ratio as a parameter. The theoreti cal results are found to be in good agreement with the experimental me asurements.