MEASUREMENT OF MAGNETIC-FIELD FLUCTUATION IN A FIELD-REVERSED-CONFIGURATION PLASMA

Confinement magnetic field of a field-reversed-configuration (FRC) pla sma is reduced by a factor of about 10 and plasma density is decreased by a factor of about 100 without lowering the temperature seriously b y translating a theta-pinch produced FRC plasma axially into a large b ore metal vessel. Reduced magnetic field brings the lower-hybrid frequ ency into a range easily detected by magnetic probes. Search for wave activities in the FRC plasma for a wide frequency range disclosed magn etic field fluctuations in the lower-hybrid-drift frequency range for the first time in the FRC plasma. The identification of the mode is no t done yet but the fluctuation level is close to the values predicted by theories on the LHD instability. This fluctuation level is not larg e enough to account for the transport rate of the particles from the F RC plasma.