Radiation Mechanism Analysis of Hypervelocity Impact Ejecta Cloud

•Three peaks exist in the evolution of the special radiation intensity with aluminum spheres hypervelocity impact aluminum thick targets.•Physical mechanism of the first radiation peak is the jetting mechanism considering the shear heating effect.•Physical mechanism of the second radiation peak is the shock-induced gasification.•Main mechanism of the third peak is the ablation of tiny fragments.•The ambient gas pressure has a significant effect on the radiation characteristics.