Electrostatic probe disruption of drift waves in magnetized microdischarges

Ultrahigh speed images of ExB discharges are collected during electrostatic probing of magnetized microdischarges. Two azimuthally separated floating micro-Langmuir probes inserted into an axisymmetric microscale magnetically confined plasma are used to characterize azimuthal drift waves. The images reveal features associated with probe intrusion, showing how the electrostatic probes may disrupt the otherwise coherent azimuthal waves. The resulting wave dispersion calculated from the probe signals is consistent with the disruptions seen in the images. These images demonstrate how probe measurements of fluctuations and turbulence, even when probe dimensions are much smaller than characteristic discharge scales, must be interpreted with caution.