Experimental investigation of electron transport across a magnetic field barrier in electropositive and electronegative plasmas

Abstract

In this paper we experimentally investigate the × E B drift of electrons in low temperature plasmas containing a magnetic field barrier; a plasma configuration commonly used in gridded negative ion sources. A planar Langmuir probe array is developed to quantify the × E B drift of electrons over the cross-section of the ion-extraction region of an ion-ion plasma source. The drift is studied as a function of pressure using both electropositive plasmas (Ar), as well electronegative plasmas (Ar and SF 6 mixtures), and is demonstrated to result from an interaction of the applied magnetic field and the electric fields in the sheath and pre-sheath near the transverse boundaries. The drift enhances electron transport across the magnetic field by more than two orders of magnitude compared with simple collisional transport, and is found to be strongly dependant on pressure. The lowest pressure resulted in the highest influence of the drift across the extraction area and is found to be 30%.

A new ion–ion plasma thruster with an annular geometry

“…Inhomogeneous light distribution as well as asymetry in plasma properties and charged particle currents have been observed and studied in several low-pressure partly magnetized discharges operating with electropositive as well as electronegative gases [20][21][22][23]. The key factor for generating an asymmetry is the magnetic field topology.…”

Instability-enhanced transport in low temperature magnetized plasma

“…The results are of importance for the modeling of industrial plasma devices such as neutral beam injectors, 18 and electric space propulsion systems. 19 In this Letter, the frequencies are normalized to the electron cyclotron frequency ω ce = eB/m e , where B is a uniform magnetic field, the length dimensions are normalized to the Larmor radius of thermal electrons ρ L = a) Electronic mail: romain.lucken@lpp.polytechnique.fr 1 eB (k B T e m e ) 1/2 , where T e is the electron temperature, that is assumed uniform, the velocities are normalized to the electron thermal velocity v T e = (k B T e /m e ) 1/2 , and the electrostatic potential φ is normalized to the electron temperature in volts. Under these conditions, the electron momentum balance equation is:…”

“…The spectral analysis of the PIC simulation results is compared with the solution of the theoretical dispersion relation, and the effective collision frequency measured in the PIC simulation is compared with the analytical model.The results are of importance for the modeling of industrial plasma devices such as neutral beam injectors, 18 and electric space propulsion systems. 19 In this Letter, the frequencies are normalized to the electron cyclotron frequency ω ce = eB/m e , where B is a uniform magnetic field, the length dimensions are normalized to the Larmor radius of thermal electrons ρ L = a)…”

“…The results are of importance for the modeling of industrial plasma devices such as neutral beam injectors, 18 and electric space propulsion systems. 19 In this Letter, the frequencies are normalized to the electron cyclotron frequency ω ce = eB/m e , where B is a uniform magnetic field, the length dimensions are normalized to the Larmor radius of thermal electrons ρ L = a)…”

Reduced-order kinetic plasma models using principal component analysis: Model formulation and manifold sensitivity

“…These correspond to two possible ionization 93 potentials when considering the ionization reactions starting from the excited states. For example, 94 Ar(2) will ionize to Ar + (1) and Ar (4) to Ar + (2). Table II shows the energy data for those two ionized 95 states.…”