Flow shear effects on plasma microinstability in open-ended magnetic configurations

The external and independent control of parallel and perpendicular flow shears in collisionless magnetized plasmas is realized using segmented plasma sources. Then, ion flow velocity shears parallel to the magnetic-field lines are observed to destabilize not only the drift-wave but also the ion-cyclotron instabilities depending on the sign of the parallel shear in the absence of field-aligned electron drift flow in laboratory experiments. On the other hand, perpendicular ion flow velocity shears are demonstrated to suppress both the drift-wave and the ion-cyclotron instabilities, and furthermore, the suppressions are found to take place independently of the sign of the perpendicular shear.