The instantaneous triple-probe method for the direct display of plasma parameters in a low density continuum plasma

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.