X-ray phase-contrast imaging (XPCI) provides superior sensitivity for the diagnosis of low-Z materials compared with absorption-based techniques. Betatron radiation generated by laser wakefield accelerators, which offers high photon flux, ultra-short duration, and relatively high spatial coherence, is a promising compact source for XPCI. At present, there is a lack of knowledge about how to control wakefield accelerators and realize high-quality XPCI. This study investigates the influence of gas pressure (plasma density) on betatron source characteristics and on the performance of propagation-based XPCI. Through particle-in-cell and wave-optics simulations, it explores the relationship between gas pressure and imaging characteristics such as spatial resolution and brightness and determines an optimal operation window. Experimental results confirm this optimal operation window at 40–45 psi plasma density ∼3–4×1018cm−3, with which a peak photon flux of 8×1012photons/sr and a contrast of 20.32% at a spatial resolution of 5 μm are realized. This study demonstrates a pathway for the optimization of betatron-based XPCI, enabling synchrotron-comparable spatial resolution in a laboratory-scale setup and shows the potential of XPCI in ultrafast microscopic imaging applications.
Fan et al. (Mon,) studied this question.