Detection of electric field around field-reversed configuration plasma

摘要

Electric-field probes consisting of copper plates are developed to measure electric fields in a vacuumregion around a plasma. The probes detect oscillating electric fields with a maximum strength ofapproximately 100 V/m through a discharge. Reproducible signals from the probes are obtainedwith an unstable phase dominated by a rotational instability. It is found that the azimuthal structureof the electric field can be explained by the sum of an n=2 mode charge distribution and aconvex-surface electron distribution on the deformed separatrix at the unstable phase. The formerdistribution agrees with that anticipated from the diamagnetic drift motions of plasma when therotational instability occurs. The latter distribution suggests that an electron-rich plasma covers theseparatrix.