Polarized pyrometric probe: principles of operation and measurement of plasma particle energy

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Abstract
The polarized pyrometric probe is a thermally insulated electrostatic probe made of tungsten or carbon. Unlike the Langmuir probe, its operating characteristic is located beyond the knees on the curve indicating ion and electron saturation. In hot, dense plasmas (where the Langmuir probe is difficult to use), the radiance of this probe, inferred from the temperature reading on the pyrometer, is compared with the product VI (voltage times current) of the characteristic. It is then easy to calculate the energy of the particles and to estimate their density. The principle underlying these measurements is explained and illustrated by two experimental applications for ions of 300 and of 1200 eV.