Use of Langmuir probes in a weakly ionized, steady-state plasma with strong magnetic field

Abstract

This article describes the use of Langmuir probes to measure plasma parameters in low density, low temperature plasmas with a strong applied magnetic field. The experiment has been performed at the Physics Department of Milan’s University on the steady-state toroidal machine “Thorello.” Results have been analyzed by taking into account instrumental and ionic sheath effects. Finally, experimental results have been compared with direct measurements of the electron distribution function in Thorello.

ECR Heating in a Helicon Device

“…where M i is the ion mass, A probe the projection of the effective area of the collecting probe in the direction of the magnetic field and k ¢ 0£ 49 is a constant which includes the influence of the magnetic field [19]. The comparison of the radially integrated ion saturaton current profile with the line integrated density as measured with the interferometer [ Fig.…”

Propagator integral method for plasma physics kinetic equations with practical applications

“…This reference voltage can be easily modified before starting the measurement process. Even when this circuit is not unique and other options exist in the literature [137], this scheme has been tested in previous works [99,100,141], providing good results and its verification or possible improvements are out of this thesis scope.…”

“…The modelisation of this interaction is usually established by models that may not capture all microscopic processes involved, specially in Weakly Ionized Plasmas (WIP) for which the inclusion of a dense heavy cold neutral species hinders the development of models [137][138][139]. Our research group is interested in the use of these probes to analyse the plasma generated in our low temperature laboratory [99,100,152], making this topic of main interest.…”

“…An important case of plasma-wall interaction appears in the characterization of plasmas, usually carried out with emissive [84,142,151] or collecting probes [134,135,137], to calculate plasma parameters such as temperature, density or plasma potential responsible of energy transference. The modelisation of this interaction is usually established by models that may not capture all microscopic processes involved, specially in Weakly Ionized Plasmas (WIP) for which the inclusion of a dense heavy cold neutral species hinders the development of models [137][138][139].…”

“…The I-V curves of collecting probes provide information about parameters such as the local plasma potential, the electron or ion temperatures and the charged species density [131][132][133]. These probes are widely used for the diagnostics of fully [134][135][136] and weakly ionized plasmas [137][138][139]. Theoretically, the operation of Langmuir probes does not depend on the shape of the signal used to bias the probe.…”