Spectral characteristics and plasma state diagnosis of highly charged iron ions in laser-produced plasma

To accurately analyze the extreme ultraviolet radiation characteristics of laser-produced iron plasmas and diagnose their state parameters, time- and space-resolved spectroscopy was employed in this work to obtain the emission spectra of the plasma in the 9.5-12 nm wavelength range. Atomic structure calculations were performed using the relativistic configuration-interaction Hartree-Fock method with the Cowan code, which determined the charge states and dominant transition arrays of highly charged iron ions. Plasma diagnostics were achieved by reconstructing the experimental spectra using the SpeIma3D spectral simulation code. The results show that the spectral peaks in the experimental spectrum mainly originate from the 3d-4f and 3d-4p doubly excited-state transitions of Fe8+-Fe12+ ions. In addition, by assuming Gaussian-distributed state parameters and solving the radiative transfer equation, the central plasma temperature of 38.4 eV, total ion number density of 5.6×1019 cm-3, and average charge state of 8.86 were inferred at a delay time of 40 ns. This study provides reliable atomic data and experimental methods for the spectral analysis and state diagnosis of laser-produced plasmas of medium and high-Z elements, and is valuable for related research in inertial confinement fusion and astrophysics.