E x B Drift of Electrons in a Radial Electric Field and Longitudinal Magnetic Field

To examine the effect of the radial electric field on the electron rotational motion under E x B field, particularly E-r x B-z geometry, for a plasma with magnetized electrons and nonmagnetized ions flowing through a uniform magnetic channel, an experimental study is conducted by applying a steady-state plasma flow along the uniform longitudinal magnetic field B-z. The argon plasma flow is generated by atmospheric-pressure dc arc discharge, followed by a continuous expansion into a rarefied gas-wind tunnel with a uniform magnetic field 0.15 T. Inside one of the magnets which is situated at rather a downstream position, a ring electrode is set to apply the radial electric field E-r. An up-down probe is employed for the analysis of the electron azimuthal rotational motion. The value of the radial electric field applied in the plasma is about similar to 150 V/m. The probe measurement indicates the E x B rotation of electrons, particularly when the radially inward electric field is externally applied, whose order is about similar to 1000 m/s. The inward electric field results in the electron rotational motion in the same direction as the diamagnetic current. On the other hand, when the outward electric field is applied, the electron rotational motion is not observed. The order of the observed electron drift velocity is consistent with the theoretical value. E x B rotation velocity is found to be almost equal to that by the electron diamagnetic current. Even without the external electric field, the observed electron saturation current indicates that there is a rotational motion of electrons, which is considered to be due to the electron diamagnetic current.