Ion flux and energy distributions at electrode surfaces in LAPPS

Summary form only given, as follows. In situ mass and energy resolved measurements of ion fluxes to a conducting electrode surface in NRL´s large area plasma processing system (LAPPS) are presented. In LAPPS, a magnetically confined high-energy electron beam is used to ionize a background gas, thus producing a high-density plasma along the beam channel that is scalable to large areas (meters/sup 2/). In the production region, the plasma is characterized by low temperatures (Te<3 eV) and high plasma densities (10/sup 9/-10/sup 12/ cm/sup -3/). Outside the beam channel, the temperature, density, and ion composition is altered by ion-neutral and ion-electron reactions. Because plasma production is decoupled from the reactor geometry, electrode surfaces can be independently located and biased. These unique features are advantageous to materials processing in that they allow for control over the flux composition and ion energies at electrode surfaces. Pulsed plasmas in noble and molecular gases are produced using a hollow cathode electron beam source. Temporally resolved ion flux and energy distributions measurements at an electrode surface located adjacent to the discharge are reported. The incident flux, sampled through a small orifice located in the center of the electrode, is analyzed via an energy selector in series with a mass spectrometer. Measurements are presented for a grounded and RF-biased electrode as a function of operating pressure, beam-electrode separation, and electrode bias. The results are discussed in terms of processing applications. Additional details concerning LAPPS are presented by co-authors at this conference.