Characteristics and structure of an axially symmetric plasma echo

Abstract

An axially symmetrical spatial plasma echo is obtained theoretically by using the Vlasov–Poisson equation system. Several features of the echo are studied by making use of this echo solution. Common linear relations between exciter grid separation l and the position of echo-amplitude maximum le are shown, and an influence of l on the amplitude is also obtained. The radial extent of the echo and the effects of the magnetic field and the plasma temperature on the echo are discussed. Most importantly, the existence of the fine structure of the echo, such as the appearance of a side lobe (besides the main lobe) in the amplitude curve and the presence of a phase gap on the interferometric phase trace were demonstrated by their appearance in this experiment. Good agreement is obtained between theory and the experimental results concerning the side lobes and the phase gaps.