Experimental study of a new mechanism of magnetic flux cumulation by the propagation of shock-compressed conductive region in silicon

Abstract

A new mechanism of magnetic flux compression proposed by one of the authors has been experimentally proved promising for the generation of ultrahigh pulsed fields. A cylindrical implosion type device is used here, and the thin metal liner normally used is replaced by a solid cylinder of crystalline or powdery silicon. As predicted by the theory, the field compression factor depends strongly on the initial density of the silicon, on the explosive, and on the scale. A typical value of the field multiplication factor is 17.8 for a 45-mm-diam silicon cylinder of density 1.1 g/cm3.

Experimental study of shock-wave magnetic cumulation

“…where B 0 is the initial magnetic field, S 0 is the initial area of the region, S(t) is the area of the region at the time t, and α is the coefficient equal, for the model considered, to the ratio of the particle velocity u to the wave velocity D. Experimental investigations of magnetic cumulation presented in [5,13] produced expected results for the silicon powder only. The model did not predict the signal recorded for metal powders (especially for heavy metal powders).…”

“…Several more comprehensive models were proposed later [9,14,18,20,21,23,[25][26][27]. These models reduce to MHD equations supplemented by the equation of state of the substance and by the law of variation of electrical conductivity under compression and heating.…”

“…Shock-wave cumulation of the magnetic field is a method for obtaining superstrong magnetic fields and high electromagnetic energy densities [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The method is based on the property inherent in a large group of materials to acquire high electrical conductivity under shock compression.…”

“…The model [3][4][5][6][7][8] was the first attempt to describe shock-wave magnetic cumulation. Several more comprehensive models were proposed later [9,14,18,20,21,23,[25][26][27].…”

“…As the parameters of state of the substance were unknown, the experiments and model problems could not be compared. The model of magnetic cumulation proposed in [3][4][5][6][7][8] is based on several assumptions: 1) compressibility of the substance is independent of the shock-wave pressure; 2) electrical conductivity of the substance emerges directly after compression in the shock front; it is constant over the layer thickness and independent of the shockwave pressure; 3) electrical conductivity of the shockcompressed substance is so high that diffusion losses of the magnetic flux in the compressed region are negligibly small. Such a model yields a simple dependence of the magnetic field on the compressed region area…”