Tunable Betatron X-rays via Plasma Density Control with Ionization Injection for Multi-Material Imaging

Experiments with the SULF-1PW laser used densities from 2×1018 to 8×1018cm−3. Photon yield was measured at four densities and remained of order 1012 photons/sr within the reported variations.

Stable Ec values, however, were established only at 2×1018 and 6×1018cm−3: 15.5±3.8 and 25.6±3.9 keV, respectively. PIC-derived trajectories show an increase of the RMS betatron amplitude proxy from 6.2 to 17.2 µm at the higher-density point, despite dephasing-induced loss of final electron energy. The harder spectrum improves penetration of an aluminum-alloy assembly, whereas the lower-density condition provides stronger edge enhancement in Teflon and a plant specimen.