Spatio-temporal evolution of the optical field on a hohlraum wall at the rising edge of a flat-topped pulse

Considering the time delay in different hohlraum wall positions caused by oblique incidence, the spatio-temporal optical field distribution characteristics of a hohlraum wall, especially during the rising edge of a flat-topped pulse, is simulated by a fast Fourier transform method together with chromatography. Results demonstrate that beam propagation along the hohlraum wall is a push-broom process with complex dynamic spatial-temporal evolution. In the first few picoseconds, the optical intensity of the front position increases rapidly, while that of the rear position is relatively weak. The ratio R of the optical intensity during the rising edge is smaller than that of the steady state. R gradually increases and finally tends to the value of the steady state with time. Calculation also shows that, with shorter total width of the rising edge, R of the optical field decreases and the difference compared to the steady state becomes larger. The evolution is more severe with smaller angle of inclination.