Intense Emission from a Grid-Stabilized Plasma Cathode

Intense emission from a grid-stabilized plasma cathode based on a glow discharge with an expanded anode area is studied. In the electrode system of the ion source, the potential difference between a large-mesh grid electrode (a hole diameter of 4-6 mm) and cathode and anode plasma reaches 200 V and the glow discharge current is up to 1 A. The current distribution over the electrodes of the plasma cathode is taken, and the dependences of the electron extraction efficiency and electron-emitting-plasma potential on the gas pressure and discharge parameters are obtained. A relationship between the geometric parameters of the grid, cathode plasma potential, and efficiency of electron extraction from the plasma is derived. It is shown that stable intense emission from the plasma cathode can be provided in wide ranges of gas pressure and discharge current by varying the geometry and mesh size of the plasma cathode grid. Discharge contraction in the grid plane at elevated gas pressures is explained. It is assumed that the emitting plasma becomes inhomogeneous due to variation in the thickness of near-electrode layers in the holes of the grid, which makes the distribution of the emission current from the plasma more nonuniform.