On electromagnetic measurements of particle velocity

One of the shortcomings of the classical electromagnetic method of Zavoisky is sensitivity to the non-one-dimensionality of the flow behind the front of the investigated wave. In this paper, it is proposed to use a four-contact gauge to correct the measurements. Two signals are detected from frames, one of which is located in a plane tangent to the front, and the other in a plane parallel to the direction of wave propagation. Next, the true velocity signal insensitive to the curvature of the front is constructed from the two signals. The second difficulty that arises in electromagnetic measurements is the large size of the gauges. Typically, the length of the working arm $L$ is about 1 cm. An analysis of the potential distribution in the gauge showed that the proposed combined gauge is equivalent to two frames of zero width, and the effective length $L$ is the distance between the midlines of the supply conductors. It is shown that the value of $L$ can be reduced to 1.5 $\div$ 2 mm with a lead width of about 0.5 mm. This makes it possible to perform local measurements at spots of millimeter size and handle small-sized charges. These improvements bring electromagnetic measurements closer to the level of modern optical techniques, at a much more modest cost of hardware.