Experimental Studies on the Injection and Containment of Electron Clouds in a Toroidal Apparatus

摘要

Studies have been conducted on the production and containment of electron rich plasmas in toroidal geometries. Electron densities in excess of 3 x 10 to the 9th power/cc have been produced and contained in toroidal magnetic fields for as much as 10 milliseconds. Studies also indicate that the optimum production of large electron densities without excessive wall bombardment should be attained with a triode type injection configuration wherein the enrgy investment in waves and electron temperature is minimized. This configuration should be located near the major axis of the apparatus. Containment is terminated when the ion density reaches about 20 percent of the electron density. The ions are shown to be produced from atoms which are released from the walls by electron bombardment associated with inefficiencies in the electron injection process. A technique for controlling this effect which involves electron prebombardment of the walls is described. (Author)