Diagnosis of electron temperature of copper foil plasmas produced at the Shenguang-II facility

Warm dense plasmas are crucial for high-energy-density physics and inertial confinement fusion research. Experiments involving laser-irradiated copper (Cu) foil were performed at the Shenguang-II facility. A highly oriented pyrolytic graphite crystal spectrometer measured the time-integrated spectral distribution of Cu under varying laser intensities. Using the two-dimensional radiation-hydrodynamics code FLASH and the spectral analysis code FLYCHK, we simulated the temporal evolution of plasma density and temperature distributions, as well as the emission intensities of spectral lines at different temperatures and densities. The simulation results revealed that the two-electron satellite lines (J) and the resonance line (W) emissions of Cu originate predominantly from the radiation region near the critical density surface, with a density range from approximately 0.5 n_c to 1.0 n_c, and radiate primarily during the laser irradiation period. By analyzing the J/W intensity ratio of the measured spectral lines, we estimated the electron temperatures near the critical-density surface under different laser intensities.