Concentration dependence of gas discharge around drops of inorganic electrolytes

K. G. Korotkov

Institute of Fine Mechanics and Optics, Sablinskaya 14, St. Petersburg 190000, Russia

D. A. Korotkin

Department of Mathematics and Statistics, Concordia University, Sherbrook West 7141,
Montreal, H4B 1R6 Quebec, Canada

~Received 14 September 2000; accepted for publication 6 February 2001!

This article is devoted to the study of image formation in gas discharge, initiated by a strong impulsive electromagnetic field around drops of four different nonorganic electrolytes. To describe the image mathematically we propose several parameters: the form coefficient ~fractality!, the entropy, and the average streamer width. We study the dependence of these parameters on concentration. The form coefficient turns out to have the best combination of stability and sensitivity in the whole range of concentrations. Statistically significant difference between the solutions and distilled water disappears at concentrations of about 2220 N. © 2001 American Institute of Physics. @DOI: 10.1063/1.1360700#

I. INTRODUCTION
Image formation in gas discharge around objects of a different nature initiated by strong impulsive electromagnetic fields ~also called the Kirlian effect! has been known for more then two centuries.1,2 So far the main direction of investigation of the effect has been purely practical; It turned
out that gas discharge images around biological objects can provide substantial information about the internal state of the object. In particular, the gas discharge images of human fingers and toes are actively used by physicians for diagnostic purposes ~see Ref. 2 for a review!. This generated a number of research works devoted to the physical nature of image formation.1,3–7 It turns out that one of the most difficult problems
is finding an adequate quantitative description of the process. The main obstacle to an effective mathematical description is the high nonlinearity of gas discharge. Moreover, this nonlinearity comes on top of extreme complexity of the biological objects themselves.

The authors of Ref. 6 compared gas discharge images around drops of water solutions of several nonorganic salts using the traditional method of gas discharge photography.

The authors introduced several numerical parameters characterizing gas discharge around solution drops, which in particular correspond to size and shape of separate streamers.

Using these parameters they were able to demonstrate essential quantitative differences between gas discharge pictures around drops of solutions of different salts at different concentrations.

However, there are several reasons which led us to attempt to further understand gas discharge around drops of different inorganic electrolytes. First, traditional gas discharge photography is largely replaced by computer image processing.

2 The images produced in this way turn out to be essentially different from the images obtained by use of standard photographic tools. Computerized gas discharge cameras have many obvious advantages, although it turns out to be difficult to directly apply the mathematical description of Ref. 6 to computer images of gas discharge. Ideally, adequate mathematical tools should be stable with respect to the method of measurement, and, in particular, to the type of device used to obtain a gas discharge image of the given object. However, they should also be sensitive enough to
reveal small fluctuations of the object.

As far as water solutions of different salts are concerned,
in our opinion, this is an excellent laboratory for testing the
methodology of gas discharge visualization before trying to
further apply rigorous mathematical tools to gas discharge
images of more complicated objects.

Therefore, the purpose of this article is twofold. First, we
introduce several mathematical parameters characterizing the
gas discharge image ~the form coefficient, entropy, average
streamer width!. All these parameters are borrowed from the
theory of signal and image processing, and appropriately adjusted
to describe the gas discharge images. Second, we test
the applicability of these parameters to explicit description of

gas discharge images around drops of different electrolytes:
NaCl, NaNO3 , KCl, KNO3 . In particular, we evaluate the
average error resulting from the stochastic nature of the gas
discharge process itself. The main focus will be on the dependence
of these parameters on concentration.

II. BASIC PRINCIPLES OF GASEOUS DISCHARGE
VISUALIZATION TECHNIQUE: EXPERIMENTAL
SCHEME
The scheme of the experiment is shown in Fig. 1. By a
vacuum photogalvanoplastic process a thin metal grid with
10 mkm wires is evaporated onto the bottom surface of the
glass plate. A train of duration 0.1 s of triangular 10 mks
electrical impulses of amplitude 3 kV, steep rate 106 V/s and
repetition frequency 103 Hz is applied to this grid.

Full text: 2001 Korotkov_Korotkin_JAPPF

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