Oxygen plasmas generated by the slot antenna type microwave plasma source are studied using the single Langmuir probe technique. Microwave power in the range from 600 to 1200 W at frequency 2.45 GHz is applied at neutral gas pressure 100 Pa. Axial distributions of floating potential, plasma potential, concentrations of electrons and negative ions and electron energy probability function are obtained. The influence of the electromagnetic field on the plasma parameter distribution is discussed on the basis of analytical formulas and numerical field computation. The experimentally obtained electronegativity α 2 is compared with the theoretical results from a simple model based on the balance equation for the negative ions.

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The spatial distribution of the plasma parameterselectron density and temperature as well as plasma and floating potentials-in the region of plasma expansion of an inductively driven low-pressure discharge in hydrogen is studied by probe diagnostics. Electron cooling and a decrease of the electron density with formation of regions with different axial gradients are outlined as basic features of the expanding plasmas. Thermal conductivity and electron energy flux from the driver are considered to be responsible for the plasma behavior at its expansion. The role of the thermal diffusion in the formation of the axial profile of the plasma density is also shown.

Summary: Results from tandem‐type probe diagnostics of a plasma source based on an inductive discharge are presented in this study. The driver region is in the classical form of a cylindrically shaped inductive discharge, with a coil positioned over a gas discharge tube, whereas a bigger metal chamber provides volume for plasma expansion. Low pressure argon discharges were studied. The axial profiles of the plasma parameters were measured in the discharge in the metal chamber. The results obtained show that decreasing electron temperature and plasma density with increasing distance from the driver characterizes the behavior of the expanding plasmas. Moreover, two regions with different rates of variation of the plasma parameters complete the plasma expansion volume: a faster drop close to the driver and slow axial changes away from it. The gas pressure and power applied for the discharge maintenance were the external parameters varied.

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