Theory of a cylindrical probe in a collisionless magnetoplasma

Abstract

A theory is presented for a cylindrical electrostatic probe in a collisionless plasma, when the probe axis is inclined at an angle ϑ to a uniform magnetic field. The theory is applicable to electron collection, and under more restrictive conditions, to ion collection. For a probe at space potential, the theory is exact in the limit when probe radius rp≪ Debye length λD. At attracting probe potentials, the theory yields an upper bound and an adiabatic limit for current collection. At repelling probe potentials, it provides a lower bound. The theory is valid if rp/λD and rp/ā, where ā is the mean gyroradius, are not simultaneously large enough to produce extrema in the probe sheath potential. The numerical current calculations are based on the approximation that particle orbits are helices near the probe, together with the use of kinetic theory to relate velocity distributions near the probe to those far from it. Probe characteristics are presented for ϑ from 0° to 90°, and for rp/ā from 0.1 to ∞. For ϑ=0°, the end-effect current is calculated separately.

Measurement of Plasma Parameters in Low Temperature High Density Hollow Cathode Plasma Jet Working in Magnetic Field

“…In this way the probe was roughly perpendicular to the magnetic field lines. Therefore, there was only weak influence of applied magnetic field on the probe characteristics [6]. The applied magnetic field was also much lower at the probe position than at the nozzle outlet.…”

Miniature ion thruster ring-cusp discharge performance and behavior

“…There are more complicated Langmuir probe theories for magnetized electron collection that may yield a more accurate plasma potential. [28][29][30] However, they are prohibitively difficult to implement in the mapping of a ring-cusp discharge since the magnetic field strength and orientation vary significantly throughout the chamber. In addition, the errors associated with the probe analysis are systematic and the results are sufficient for a qualitative comparison between the various discharge conditions.…”

Spatiotemporal temperature fluctuation measurements by means of a fast swept Langmuir probe array

“…It is assumed that T i = T e in the edge plasma of the W7-AS. Since the tip dimensions are small compared to the mean free paths of the plasma particles, and large compared to their gyro radii and to the Debye length, the use of theory for a classical Langmuir probe in a strong magnetic field [25] is appropriate. I sat is thus related to the ion current density according to…”