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The calibration of electrostatic triple-probe voltage and current response in a supersonic continuum plasma has been carried out using a low-pressure shock tube. The electron temperature Te and charge number density Ne are compared to probe voltage and current response, respectively, for a useful range of plasma parameters (1≲Rp/λD≲10, 2≲M≲5, and 7<φ13<35, where Rp is the probe radius, λD is the Debye length, M is the shock Mach number, and φ13 is the nondimensional probe voltage). The dependence of probe response on Debye ratio Rp/λD and various flow parameters was investigated. The probe voltage response was found to depend significantly on the Debye ratio. Expressions for electron temperature determination by triple probe are presented.

An exact theory is developed for the use of the instantaneous triple-probe method in the continuum Laplace limit. The theory applies to probes of arbitrary shape, including the commonly used spherical and finite cylindrical probe configurations. The theory yields the same form for the probe characteristic for all probe shapes. The theory is also extended to deal with the effects of the presence of negative ions. An experimental confirmation of the theory has been carried out both in glow discharge and discharge afterglow plasmas.

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