Potential well formation in electrostatic confinement devices. Technical progress report

Abstract

Electron injection experiments on the large spherical inertial electrostatic plasma confinement devices have been extended to much higher voltages and currents (up to 10 kV and up to 25 A). Electron beam diagnostics have verified the production of a deep negative electrostatic well under high vacuum conditions and a multiple potential well when low pressure deuterium is added. A movable electrostatic probe has been constructed and has been used to show that the ions produced within the chamber can be focussed towards the center of the device with very low divergence. Additional theoretical work has been done to clarify the electron and ion parameters for which a triple well structure (trapped ions or trapped electrons) can be expected to be produced. A small hydrogen negative ion source has been constructed and is under study as a possible source for ion diagnostics.