Mapping and analyzing plasma parameter distribution in low-temperature plasma using collecting and emitting probes.

Understanding the electric field profile in plasma is crucial in studying dusty plasma dynamics. Because many dusty plasma experiments are performed at relatively low input powers (< 5 W using a 13.56 MHz radio frequency generator) and at higher neutral pressures (~20 to 200 mTorr), diagnosing these weakly ionized, low-temperature plasmas can be challenging.  The goal of this study is to evaluate the use of different in-situ probe techniques for determining the electrostatic potential structure of the plasma. A Langmuir probe is used to map the spatial distribution of plasma density (n_e), electron temperature (T_e), and floating potential (V_f) within a plasma chamber. Emissive probes are used to measure the plasma potential. The electric field in the plasma chamber will be determined over a range of RF power and neutral gas pressure.  A comparison is made between potential measurements from the emissive probe and the calculated potential from the Langmuir probe to determine the relative accuracy of each diagnostic technique. This study helps to evaluate the discrepancies in different measuring techniques and understand how the plasma parameters behave as they approach the sheath and plasma boundaries.

This research is supported by the US Department of Energy FY2020 Early Career Award DE-SC0021106, Facilities Award DE-SC0023416 from the Office of Fusion Energy Science and US Army Research Office - Sciences of Extreme Materials Branch Award #W911NF-23-2-0013