The physics of positively biased conductors surrounded by dielectrics in contact with a plasma

Abstract

The physics of a positively biased conductor surrounded by dielectrics in contact with plasma is investigated. It is shown that because of the presence of secondary emission from the surrounding dielectrics the voltage of the surfaces near the conductor has three solutions. Of the three possible solutions, the high- and low-voltage solutions are stable while the intermediate voltage solution is unstable. For the stable solutions, the low-voltage solution always has very low secondary emission while the high-voltage solution has high secondary emission. The secondary current emitted from the neighboring dielectrics is collected by the conductor. When the voltage on the dielectric undergoes a transition from one bistable solution to another this will be seen as a concomitant increase in the current collected to the conductor. This theory is applied to explain the ‘‘snapover’’ effect. The snapover effect is observed on high-voltage solar arrays that involve the use of highly biased surfaces in contact with the space environment. It has been observed that when such surfaces are postively biased the current undergoes an anomalous increase at a critical voltage.