Radio frequency Langmuir probe

A Langmuir probe for measuring characteristics of a plasma driven by radio frequency (RF) power, the probe comprising an elongated conductor having an exposed tip for insertion into an RF plasma and an outer end for connection to external measuring circuitry, and an RF voltage divider in series between the tip and outer end of the conductor, wherein the conductor is surrounded by a hollow dielectric tube, and wherein the voltage divider comprises at least two impedances disposed in series with the conductor and respective shunt capacitances, at least one impedance being located within the tube and at least one capacitance being in the form of an electrode on an outside surface of the tube, the impedances and capacitances alternating in the longitudinal direction of the tube.