Emissive probe current in response to time-varying probe bias voltage

Applications of biased emissive probes for measurements of the plasma potential [1] require an understanding of the dynamic response of the probe current to time-variations of the sweeping probe bias voltage. In this work, we explore fundamental and technical limitations of emissive probe measurements with a changing bias voltage at timescales both slower and faster than the inverse of the ion plasma frequency. The focus is on measurements of the time-evolution of the probe current as the sheath between the plasma and a strongly emitting probe restructures in response to the bias change. A comparison of experimental results with simulations [2] will be discussed.

[1] J. P. Sheehan, Y. Raitses, N. Hershkowitz, I. Kaganovich, and N. J. Fisch, Physics of Plasmas 18, 073501 (2011).

[2] G. R. Johnson and M. D. Campanell, Plasma Sources Sci. Technol. 30, 015003 (2021)