IMPURITIES, TEMPERATURE AND DENSITY IN A MINIATURE ELECTROSTATIC PLASMA AND CURRENT SOURCE

We have spectroscopically investigated the Sterling Scientific miniatu re electrostatic plasma source-a plasma gun. This gun is a clean sourc e of high-density (10(19)-10(20) m(-3)), low-temperature (5-15 eV) pla sma. A key result of our investigation is that molybdenum from the gun electrodes is largely trapped in the internal gun discharge; only a s mall amount escapes in the plasma flowing out of the gun. In addition, the gun plasma parameters actually improve (even lower impurity conta mination and higher ion temperature) when up to 1 kA of electron curre nt is extracted from the gun via the application of an external bias. This improvement occurs because the internal gun anode no longer acts as the current return for the internal gun discharge. The gun plasma i s a virtual plasma electrode capable of sourcing an electron emission current density of 1 kA cm(-2). The high emission current, small size (3-4 cm diameter), and low impurity generation make this gun attractiv e for a variety of fusion and plasma technology applications.