Cathode development for LAPPS

Summary form only given. NRL is developing a Large Area Plasma Processing System for materials processing applications. 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 confined 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/sup 2/ using a 60 cm long by 1.9 cm diameter cylindrical, hollow cathode. Continuous (CW) beams have been produced at up to 6 keV using both cylindrical and rectangular hollow cathodes operated at low voltage followed by a high-voltage acceleration stage. The beam 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. Langmuir probe data is used to determine the properties of the plasma produced by the CW electron beam. This data will be presented for each gas. Beam profile measurements, which are made with grounded, interceptive probes, will also be presented.