Effect of Orifice Diameter on the Performance of a Miniature Microwave Neutralizer

A miniature electron cyclotron resonance (ECR) plasma source is operated as a neutralizer, and the effect of orifice diameter on the output is studied. The output is quite promising for accompanying 1-mN-class ion thrusters with an output ion-beam current of 12–15mA. The optimum orifice diameter is independent of neutral mass flow rate, implying that factors other than electron-neutral collisions are dominant. The variation in orifice diameter is expected to alter the microwave field boundary conditions inside discharge chamber (DC), and also influence the dc-electric field existing between the orifice and collector. The convolution of these two factors would be primarily responsible for the optimum orifice diameter.