Design of an electrostatic end-plugged plasma-confinement device

Abstract

A laboratory-scale experimental device having an outside diameter of 1.2 m has been designed to test the idea of electrostatic end plugging of an open-ended magnetic-field configuration. The configuration is a toroidal quadrupole having four very thin (less than 1-mm-thick) line cusps produced by four circular copper coils. Iron is used to concentrate the magnetic flux density to 2.0 T; without the use of iron, the power consumption, which is about 1 MW, would be about 25 times higher. The use of iron also produces a precisely known magnetic field and allows good access for diagnostics and pumping. Iron is also used for both the flux return path and the vacuum chamber. A hollow anode with an adjustable (nominally 1-mm-wide) gap is biased from 10 to 20 kV. Plasma densities of about 10/sup 13/ cm/sup -3/ and temperatures of about 1 keV might be produced by an electron beam and by electron cyclotron resonance heating. Higher-order multipoles (hexapoles and octopoles) also are described