Accurate space potential measurements using an emissive probe in high pressure plasma and neutral gas

Abstract

The accurate measurement of plasma potentials at high pressure is investigated with an emissive probe. The emissive probe I-V characteristic of argon plasma obtained at 100 Pa is interpreted in detail, showing two inflection points in the I-V trace. Accurate plasma potentials at high pressure can be determined from the first inflection point potential (the higher potential) by using the improved inflection point method of the emissive probe, while the second inflection point is a result of the additional ionizing phenomenon caused by the collision between the emitted electrons and the neutral argon atoms. Additionally, the accuracy of the plasma potential measurement at high pressure is verified to be within 0.3 V, confirmed by the measurement of space potential distribution between two parallel plates in neutral gas at 100 Pa. The accurate measurement of space potentials in high pressure plasma and neutral gas indicates that the improved inflection point method of the emissive probe approach is promising in the study of collisional sheath structures and electrostatic probe diagnostics of high pressure plasmas.