A Modified Steady-State Method for Space Charge-Limited Effect of SGEMP

Excitation of the system-generated electromagnetic pulse (SGEMP) effect by high-dose X-rays in a cavity may induce the high space charge-limited (SCL) effect. This nonlinear effect limits the photocurrent from the electron emission surface, thereby limiting the increase in the SGEMP electromagnetic field. A modified steady-state approximation method is derived, which considers the influence of electron velocity and the relativistic effect on the number and motion of electrons, respectively. It can be applied to simulate the motion of electrons with a discrete spectrum. Compared with the original method, this method obtains more accurate results for an increase in energy. The method can be applied to the simulation of a cavity SGEMP with the boundary layer treatment. The results show that the increase in the electron yield may induce a nonlinear change in the peak value of the electric field; however, the frequency spectra are less affected. The influence of the SCL effect on lower-energy electrons is higher than that on higher-energy electrons. With an increase in lower-energy electrons in the energy spectrum, the excited electric field is affected more significantly by changes in the energy spectrum, owing to the SCL effect.