Apparatus for generation of nanojoule-class water-window high-order harmonics

In our recent study [Fu et al., Commun. Phys. 3(1), 92 (2020)], we have developed an approach for energy-scaling of high-order harmonic generation in the water-window region under a neutral-medium condition. More specifically, obtained nanojoule-class soft x-ray beam phase-matching It has been achieved by combining newly terawatt-class mid-infrared femtosecond laser and loose-focusing geometry generation. The generated is more than 100 times intense compared to previously reported results. experimental setup included two key parts: terawatt driving Sci. Rep. 8(1), 7692 (2018)] specially designed gas cell. Despite dramatic drop optimal pressure due geometry, it still reached 1 bar level helium. Thus, double-structured pulsed-gas cell with differential pumping system, which enabled providing sufficiently high pressure. Moreover, allowed reducing consumption significantly. A robust energy-scalable apparatus this will enable over ten-nanojoule attosecond pulses near future.