Influence of eddy-current on inside magnetic field distribution in vacuum electronic devices and corresponding suppression methods

Excitation of magnetic field with short pulse current coils is one of the important technological approaches for achieving ultra-strong magnetic field in high frequency vacuum electronic devices, in which eddy-current would be excited at the same time and influence the distribution of magnetic field inside the tube. Impact of eddy-current on the distribution of short pulse magnetic field is studied in this paper, the effects of pulse duration, conductivity and thickness of the metallic structure on eddy-current are analyzed. The results show that the influence of eddy current on the internal magnetic field increases with the decrease of the pulse width of the coil current, the increase of the conductivity and the thickness of the metal, which leads to failure of effective excitation of magnetic field inside the tube. Two methods for suppressing eddy current are proposed including electroplated coating of good conductor on high-resistivity metallic material and longitudinal slotting, the calculation results show that the two methods could effectively depress the influence of eddy-current on the distribution of magnetic field in the device.