Application of Plane Probe to Weakly Ionized Plasmas.

Abstract

Probe characteristics are numerically obtained in a wide range of electron temperatures and densities for the collision-dominated plasma sheath in which the fundamental Langmuir theory of the electrostatic probe fails. The asymptotic theory of Cohen for continuum conservation equations is applied to the ellipsoidal probe, and to the plane probe as the limiting case. It is found that, for the collision-dominated plasma sheath, significant errors in measured electron temperature are expected if the fundamental Langmuir theory is used to evaluate the temperature from the measured probe current and voltage. For quick evaluation of the electron temperature in such plasmas, the bound triple-probe method is proposed, and numerical results are summarized in a graphical form for practical use.