A Large-Area Dc Grid Anode Glow Discharge in Helium
A grid anode glow discharge is a promising source of plasma for absorbing electromagnetic radiation. This paper presents an experimental study of a large-area DC grid anode glow discharge in helium. The behavior of the helium discharge was studied at pressures in the range of 2–50 Torr and discharge voltages up to 1500 V. It was observed that the discharge completely covered the cathode surface at helium pressures of 2–25 Torr. For all pressures, voltage increases as current increases, typical for anomalous glow discharge. The electron density in the post-anode plasma and attenuation of the microwave radiation by the plasma were measured using microwave diagnostic methods. It was found that the electron density and degree of helium ionization decrease with increasing helium pressure and increase with increasing discharge current. The electron density in the post-anode plasma is not high: <i>n<sub>e</sub></i> is about 2 × 10<sup>9</sup>–6 × 10<sup>10</sup> cm<sup>–3</sup>, corresponding to a degree of ionization of about 10<sup>–7</sup>–10<sup>–6</sup>. It is shown that the maximum attenuation of 10-Ghz microwave radiation is about 6% at a helium pressure of 2 Torr.