Electron Sheaths in Low-Pressure Weakly Collisional Plasma

Summary form only given. Electron sheaths are normally only present near small probes when they are biased more positive than the plasma potential or at electron emitting surfaces in weakly collisional low pressure plasma. Here, electron sheaths created along the axis of a large positively biased plate (diameter = 10 cm) located in a multi-dipole argon plasma are described. Experimental data show that the electron sheath can collect all electrons produced by ionization if sufficient loss area is provided for ions at the chamber walls. Measurements of the plasma potential with emissive probes and Langmuir probes show potential dips form at the sheath edges to limit electron loss and increase ion energy. The use of electron sheaths for extracting electron beams from plasmas will also be discussed