352 / 2019-02-27 14:25:21

A numerical method for analyzing plasma expansion in rod-pinch diode[]

flash radiography source,rod pinch diode,expansion of electrode plasma

全体主题 > Fundamental Physics at Extremes

The rod pinch diode is a cylindrical pinched beam diode that generates an intense pulsed small diameter bremsstrahlung source for flash radiography. The intense electron beam is generated from cathode by explosive electron emission. In this process, the plasma is formed on the cathode surface due to the supply of the high voltage pulse. The anode plasma is produced when the intense electron beam bombards the anode, and the energy deposited by electrons is large enough to heat the surface temperature to a few hundred degrees. The radial expansion of electrode plasma shortens the gap between the cathode and anode，it also degrades the performance of the diode. To study the plasma expansion velocity, we have taken four experiments with different ratios of the cathode to anode radii at 1 MV. A numerical method is proposed to evaluate the anode plasma expansion velocity with the numerical solution of the critical current model at the magnetically limited phase. This method features a fast analyzing process that directly obtains the average anode plasma velocity. With this method, the fitted diode currents agree well with experimental results, which proves that the calculated velocity is usable to analyze the gap closure process, and to evaluate the performance of the rod pinch diode.