kHz tabletop coherent soft X-ray source enabled by single-stage 10 mJ Ti:sapphire amplifier

We present a tabletop source of bright, broadband, soft X-rays with photon energies up to 300 eV. By driving the harmonic generation process using 1.3 $\mu $m light in a high-pressure, phase matched geometry, we significantly enhance the soft X-ray flux and stability. We achieve a photon flux \textgreater 10$^{8}$~photons/s/1{\%} bandwidth, which emerges as a soft x-ray supercontinuum. Utilizing this broad bandwidth, we can implement high-quality x-ray absorption spectroscopy of multiple elements and transitions in a single spectrum. Near edge fine structure is obtained from molecular samples (CS$_{2}$ and SF$_{6})$. Furthermore, we demonstrate the applicability of this source to transient absorption studies by measuring the transient soft X-ray absorption of xenon plasma with high spectral sensitivity and femtosecond temporal resolution.