Charge depletion downstream of a cylindrical Langmuir probe immersed in a flowing, high-pressure plasma

An experiment performed to examine the charge-depletion downstream of a cylindrical Langmuir probe immersed in a flowing, high-pressure plasma is described. A cylindrical electrode, negatively biased to collect ions, was placed in an atmospheric pressure, premixed air/propane flame. A small Langmuir probe was used to observe the removal of ions downstream of the electrode, and a laser anemometer was used to measure the velocity of the flame gases near the electrode. This procedure results in a unique confirmation of the thin-sheath and thick-sheath equations for cylindrical Langmuir probes, without the necessity of having an absolute calibration of the flame density