Heterogeneous development of decomposition reactions of shock-compressed homogene ous explosives

Abstract

and based on the use of light beams with a wide aperture. The advantage of these beams is revealed here in more detail than previously, and new experimental results are discussed. The scheme of the corresponding experiments is described in [8, 9]. The image of an extraneous light is focused on a thin, plane layer of liquid enclosed between metal screens, by means of an absorbing lens and with the passage through it of a shock wave, and in the experiment the variation with time of the intensities of the reflected and scattered beams is recorded as a function of the surface nature of the screen (mirror, matte, black). From these data, the dimensions and volume concentration of the scattering centers or the average distance between them were determined. We shall show the feasibility of these estimates for the most widespread case, when the scattering centers have a sharp characteristic curve, i.e., scattering takes place predominantly at small angles to the direction of the transmitted beam of light. This requirement is achieved in all the experiments described below. In this case, it is simplest to consider direct beams in place of reflected beams, passing through an imaginary layer of liquid, which is adjacent to the layer being investigated, and which is its mirror image relative to this surface [10]. In describing the latter property of the ideal mirror, we shall assume that the boundary between these layers is completely transparent {strictly speaking, the transmission coefficient should be described by it, equal to the coefficient of reflection of the mirror, but such accuracy is not necessary). It is obvious that the wider the aperture of the incident light beam {i.e., the greater the relative opening of the focusing system in the experimental scheme being considered), the greater is the accuracy with which the beams of the transmitted and scattered light can be assumed to be superposed, despite the second one always being wider. It is precisely this that is the advantage of wide-aperture beams. It reduces to the fact that along any ray not very close to the edge of the light beams, the total intensity of the transmitted and scattered light is reduced almost only because of its absorption in the scattering centers. Consequently, along this ray we have Ii = l0 exp (- K~a~Nl),