Point to plane

The desctiption of SF electtical properties needed for practical appHcations is more complex than knowledge of BDV. Corona-onset voltages (COV) must be considered, particularly for the more usual nonuniform fields. Figure 2 illustrates this for a point-to-plane electrode configuration, where extensive prebreakdown corona occurs before sparkover (36). 

The SSMS point-to-plane surface technique has been shown to be particularly useful in the survey analysis of epitaxial films, heavy metal implant contamination, diflRision furnace contamination, and deposited metal layers. 

Figure 4 SSMS surface analysis. The point-to-plane technique allows ppma elemental surveys over a depth of 1-5 xm.

Takaki, K., Jani, M.A. and Fujiwara, T. (1999) Removal of nitric oxide in flue gases by multi-point to plane dielectric barrier discharge, IEEE Trans. Plasma Sci. 27, 1137—45. 

No attempts to calculate those limiting surface field intensities or gradients for small particles have been reported in the literature. However, point-to-plane corona has been studied in detail. Loeb (L8) has proposed a method for calculating positive corona threshold limits making use of established values of the Townsend first ionization coefficient. Loeb s threshold formula is... 

Figure 4. Most studied electrode geometry in liquid corona discharge reactors (A) point-to-plane and (B) plate-to-plane.

But where did the calibration plane come from By letting the computer use the same statistical tool that it used before the least squares best fit. Only this time it operates with one more dimension. Initially (in order to calibrate the system) one obtains a so-called "learning set" of standards (samples which have been analyzed by some acceptable reference method). Each sample is then measured at each wavelength and the absorbances are plotted in three dimensional space rather than in the plane of a sheet of graph paper. The residuals (distances from point to plane) are minimized by the least squares algorithm, and the plane which fits best through these points is, by definition, the calibration plane (see Figure 10). 

The direct tomographic technique can be further subdivided according to the detector area into which a certain elemental volume in the object can radiate. For the case of a primary beam confined to a 1-D pencil beam, these include the point-to-point, point-to-line, line-to-line and point-to-plane variants [35],... 

Trichel, G.W. The mechanism of the negative point-to-plane corona near onset. Phys. Rev. 1938, 54, 1078. 

Suhr H. and Weddigen, G. Reduction of nitric oxide in flue gases by point to plane corona discharge with cataiytical coatings on the plane electrode Combust. Sci. and Techoi. 1990,72,101-115... 

Spectrochemical Analysis of Aluminum and Its Alloys by the Point-to-Plane Technique Using an Optical Emission Spectrometer, in Methods for Emission Spectrochemical Analysis, 6th ed., Philadelphia American Society for Testing and Materials, 1971, pp 196-207, ASTM E 227-67. 

If you were given a brass block for analysis and told that the tin and zinc distributions in the block were very heterogeneous, would you or would you not choose a spark point-to-plane technique for analysis On what grounds do you make your selection If you chose not to use a spark point-to-plane technique, what alternative spark techniques might you employ for the analysis of zinc and tin ... 

A sample of an unknown light-metal alloy was analyzed using the point-to-plane spark technique. By means of a projection comparator the following wavelengths were identified. What elements are present (Hint the CRC Handbook of Chemistry and Physics contains lists of wavelengths.) What is the alloy matrix ... 

Figure 12-20. Point-to-plane plasma discharge system for pulsed corona discharge and spark in water.

Point to Plane Electrode 25 mil gap, 500 volts/sec. rate of rise. 

The ion chemistry and electrical stability of a point-to-plane corona discharge (CD) ion source was described using a tandem mass spectrometer equipped with an atmospheric pressure source. This source was a continuous current-regulated discharge with a direct current (DC) power supply and danonstrated the regions of stability with potential and distance between the needle and plane. A sch atic overview of the mechanism of formation of ions in a CD is shown in Figure 4.1. 

In a pulsed CD, the formation of ions is initiated with a fast increase in the electric field, commonly near a point-to-plane or point-to-surface discharge. The common... 

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