Study of Drift-KH type Fluctuations in PHASMA*

A single flux rope is created with a pulsed plasma gun in the cylindrical PHASMA (PHAse Space MApping) device. Correlated density and potential fluctuations are observed is in a region of the plasma with strong density and potential gradients. In such devices, space charge or/and net current can develop in a perturbed, electrostatic, inhomogeneous plasma with a background electric and magnetic field. The result is perturbed electric fields that drive perturbed EB drifts, causing instability growth and generating correlated strong density and potential fluctuations. In the PHASMA, observed fluctuation frequencies vary radially from above the ion-cyclotron frequency (f>fci) to below the ion-cyclotron frequency (f). The typical fluctuation characteristics are consistent with the drift-KH instability. Details of spectral features will be presented and the effects of changes in the axial magnetic field strength and neutral pressure are described.