Collisionless electrostatic single-probe and double-probe measurements

Abstract

An algebraic fit is made to the results of a numerical analysis describing the collisionless current attracted to cylindrical Langmuir probes whose ratios of probe radius to Debye length are of moderate value. The probe currents indicated by these expressions are compared to some numerically computed values and to values obtained using an approximate analytical solution. This algebraic description of the single-probe response is then used to derive the double-probe characteristics in the region where the current attracted to the probe is potentialdependent. Equations are derived and methods are discussed for accurately determining both electron temperature and number density from these double-probe characteristics. The analogous results for double-probe operation in the region of orbital-motio n-limited current collection are also included.