Abstract
plasma. The three different shapes of the probe surfaces, square, rectangular, and circular, were employed in the experiment. The surface temperature was varied between 300° and 1100CK. The main point to be noted is that the areas and the separation distance of the two probe surfaces for all cases were much greater than the thickness of the shear layer, thus satisfying one of the major conditions of the theory of Ref. 9. The comparison between the Chung theory8-9 and the experimental results of Bredfeldt et. al., published in Ref. 12, is not valid because, among other things, the main conditions previously mentioned (upon which the Chung theory is based) were not satisfied in the experiment.12 No systematic differences in the results were found between the various shapes of the probe surfaces. In Fig. 3, obtained from Ref. 11, the measured values of nem by a microwave technique are plotted against those obtained by the flush double probes via the Chung-Blankenship theory.9 In translating the flush double-probe readings to neoo, Thompson employed the general sheath correlation equation of Eq. (17) given in Ref. 9, the validity of which is not limited to the conical bodies. In reducing the double-probe data by Eq. (17) of Ref. 9, Thompson employed Sd = 1, for then the best correlation was possible. As it was stated in Ref. 9, the flush probe theory was developed with added approximations to the parallel probe analysis. Hence, one can not be too specific here about the ion Schmidt number. We may only state that Fig. 3 shows a general agreement of the experimental results with the theory for the ion Schmidt number of order one. The details of the experimental work leading to Fig. 3, as well as other related materials, will be published by Thompson at a later date. Concluding Remarks The correlated diagnostic equations for electrostatic parallel double probe have been generalized for arbitrary ion Schmidt numbers. The theory developed in Refs. 8 and 9 agrees satisfactorily with the experimental results of Refs. 10 (parallel probe) and 11 (flush probe). Further comparisons will be possible as more experimental results become available, and refinement of the present theories should then follow.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have