Enhanced Experimental Techniques to Increase the Current in a Thermionic Emission Physical Plasma System for Practical Applications

Abstract

The thermionic emission phenomenon is often overlooked when it comes to implementing practical applications using physical plasma discharges even though it can be more important than the photovoltaic effect for instance [1] . The reason for this little interest is the existence of the space charge effect that limits the current flowing from the plasma discharge cathode toward the anode when more current is needed for practical applications [2] . This contribution reviews experimental techniques used to overcome this limiting space charge effect in a thermionic emission plasma system allowing for a substantial current to flow toward the anode. These experimental techniques include leaking chemical impurities to the plasma system and changing certain anode conditions [3] . In addition, a Langmuir probe is to be used and operated in the "charge collection" mode to map the electric field trajectories between the cathode and the anode with a size that is much smaller than the plasma chamber size [4] . This ensures minimal distortions of the measured physical plasma system electric field. Further, it will be demonstrated that the current drawn using these techniques is sufficient to be applied in important plasma applications such as the sputtering of metal targets to produce metal fine powders [5] .