Behaviour of small induction coil for electromagnetic confinement process

The distributions of magnetic flux densities of two kinds of induction coil with a trumpet inside wall and with a vertical inside wall have been measured by means of a detection coil and a position system. The shape and size of liquid metal meniscus were determined by measuring the quenched metal meniscus under electromagnetic pressure. By comparing the induction coil with a vertical inside wall and that with a trumpet inside wall, it was found that the later had a steeper distribution of magnetic flux density along axis. The electromagnetic pressure acting on the surface of liquid metal meniscus with a vertical periphery was nearer to the static pressure produced by liquid metal column. The vertical periphery of meniscus ensured the following advantages: uniform cross-section, smooth surface, good coupling with temperature field and steady processing. In this kind of coil the maximum magnetic flux density was at the bottom; thus it was easier for the induction coil to contain the liquid metal column when the position of S/L interface fluctuated during this processing. In addition, experimental results show that the magnetic flux density of coil with round cross section was nonuniform, it was found that square cross section was much better. There appeared a reduced flux density at the region between coil turns that caused a fluctuation of electromagnetic pressure on the surface of liquid metal and caused the sample to be nonuniform in cross-section and the surface to be not smooth.