Hollow-Cathode Development for Use as a CW Plasma Source

摘要

NRL is developing a Large Area Plasma Processing System (LAPPS) for materials processing applications. The goal is to develop a uniform plasma source that is 100 cm by 100 cm in size. The plasma generation technique utilizes a sheet electron beam to ionize a low density, neutral background gas (oxygen, nitrogen, argon, or neon). The beam electrons are generated by a separate cathode located outside the processing region and continued to a narrow channel by a transverse magnetic field of 100-300 Gauss. Plasma production is confined to the beam channel and can be pulsed or continuous. Pulsed beams have been produced at up to 5 keV and 20 mA/cm using a 60 cm long by 1.9 cm diameter cylindrical hollow-cathode. Continuous beams have been produced at up to 6 keV using both cylindrical and rectangular hollow-cathodes operated at low voltage (200-400 V) followed by a high-voltage acceleration stage. These electrons have a propagation range of several hundred cm in the neutral gas background within the 20-200 mTorr operating pressure range of the system. This paper will describe the development work to date on cathodes for the continuous source.