Hydrodynamic simulation of gold ion distribution in dual-pulse laser plasma to enhance soft x-ray emission

Abstract The temporal and spatial distributions of highly charged gold ions (Au 19+ –Au 34+ ) generated by a double-pulse laser-produced plasma were investigated via the one-dimensional Lagrangian hydrodynamic simulation code Med103. The prepulse and main-pulse durations were set to 10 ns and 100 fs, respectively. The prepulse intensity was fixed at 8.5 × 10 11 W cm −2 , with a delay of 5.8 ns between the two pulses, whereas the main-pulse intensity was varied at 6.3 × 10 14 , 6.3 × 10 15 , 7 × 10 16 , and 6.3 × 10 17 W cm −2 . The results reveal that an intensity of 7 × 10 16 W cm −2 is optimal for generating medium- to high-charge states (Au 25+ –Au 30+ ). In addition, lower charge states (Au 19+ –Au 24+ ) maintain a relatively high ion fraction (>0.2) across all intensities, primarily due to their sensitivity to the prepulse parameters. This study presents a systematic evaluation of charge-state distributions as a function of main-pulse intensity under fixed prepulse conditions. The results improve our understanding of double-pulse plasma dynamics and support the optimization of soft x-ray sources operating in the water window range (2.3–4.3 nm).