EXPERIMENTAL DETERMINATION OF ION EXCITATION ENERGIES AND DENSITIES IN A LOW PRESSURE DISCHARGE.
Final scientific rept., May 64-Jul 65,
SYSTEMS RESEARCH LABS INC DAYTON OHIO
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An experiment is described for measuring the relative population densities of the energy levels of a neon plasma using a tuneable helium-neon laser. Absorption measurements of the laser irradiation upon a neon plasma are made. A phase sensitive lock-in amplifier is used as a detector which measures only the absorption of incident laser radiation and thus eliminates erroneous measurement of background light. Two specially constructed plasma diagnostic instruments are described. The first instrument measures the second derivative of Langmuir probe current with respect to probe voltage, and thus is a measure of the electron velocity distribution in a plasma. This instrument employs a phase sensitive detector which is a theoretically optimum technique for detecting small signals in the presence of noise. The second instrument is a simple logarithmic amplifier which displays, on an oscilloscope, the logarithm of the Langmuir probe current. The slope of the resulting oscilloscope trace is a measure of the electron temperature of the plasma. Author
- Plasma Physics and Magnetohydrodynamics