Optimization of 1.6–4.0 keV broadband x-ray backlighting source from high-<i>Z</i> mixture plasmas irradiated by intense nanosecond laser

Abstract A bright x-ray backlighter with a broad spectrum in the multi-keV range is essential for diagnostics of opacity and plasma states in high-energy-density physics. This paper experimentally investigates the x-ray conversion efficiency (CE) and spectra across the 1.6–4.0 keV range for three types of material targets irradiated by lasers: Au films, Au foams, and WBi mixture films. The multi-keV x-ray CE of WBi mixture targets is approximately 34% and 17% higher than that of the Au film and Au foam targets respectively, and the backlighting spectral ranges of the Au and WBi targets are the spectral ranges of Au 4f–3d, W 4f–3d, Bi 4f–3d, and Au 5f–3d transitions are complementary in multi-keV range. Consequently, a combination of Au, W, and Bi is proposed to generate a bright and broadband x-ray source that covers the entire 2.0–3.8 keV range, which will have extensive applications in x-ray absorption spectroscopy.