Abstract: With a view to enabling errors in the space potential to be automatically corrected by detecting a floating potential in each of a plurality of probes and to remove the errors in measurement based on the corrected space potential to thereby realize the accurate measurement of the space potential, there is provided a triple-probe plasma measuring apparatus, which comprises: a circuit for measuring electron temperature and electron density of a plasma with use of triple probes; a circuit for detecting and holding a floating potential difference; a differential voltage adding circuit; a fixed voltage source; and a change-over switch, the apparatus being capable of determining a difference in the floating potentials at the position of said probes, and superimposing the potential difference determined on the fixed voltage.

Abstract: A plasma stabilizing apparatus having circuits for measuring electron temperature and electron density of a plasma using triple probes, a plasma gas pressure control circuit, and a plasma excitation power control circuit, for automatically stabilizing the plasma.

Abstract: A plasma diagnosing apparatus for performing plasma diagnosis witch probes having a high degree of cleanliness by removing contamination caused by reactive plasma, etc., while quantitatively detecting a degree of the contamination of the probes. The disclosed apparatus avoids the disadvantages of conventional apparatuses, in which the voltage-current characteristics of the probes are deteriorated by growth of the contaminant film formed on the probes, making it difficult to measure the parameters of the plasma conditions.