Speaker
Description
Langmuir probes are widely used for local plasma diagnostics, but the extraction of reliable parameters from current–voltage characteristics strongly depends on the plasma regime and on the validity of the underlying sheath and electron-kinetic assumptions. This is particularly relevant for cylindrical probes operated in RF discharges, ECR ion sources and fusion-relevant plasma sources, where density, temperature, pressure, collisionality and plasma composition may vary over broad ranges.
A modular analysis framework is developed to compare complementary interpretations of single-probe I–V curves, combining ion-current scaling, sheath-corrected descriptions, floating-potential-based estimates, iterative density reconstruction and EEDF-derived quantities from the second derivative of the probe characteristic. The aim is not to select a single universal model, but to identify the range of mutual consistency of different diagnostic estimates when moving from thick- to thin-sheath conditions, or when the electron population departs from a single Maxwellian distribution.
Special attention is given to cases showing multiple slopes in the electron retardation region, which may indicate cold and hot electron populations or a more general non-Maxwellian EEDF. The same approach is suitable for electronegative plasmas, where negative ions can affect sheath properties and current balance. The method provides a practical cross-validation tool for probe measurements in plasma sources with changing operating conditions, highlighting inconsistencies related to sheath physics, electron kinetics or plasma composition.