Vacuum-compatible sub-micrometer liquid flat-jet apparatus for soft x-ray spectroscopy

We have developed a vacuum-compatible liquid flat-jet apparatus that delivers stable, sub-micrometer sheets for soft-x-ray spectroscopy. Interchangeable PEEKsil microjets (ϕ 25-100 μm) collide to form a leaf-like jet that runs reproducibly for more than 6 h at ∼0.1 Pa. A stepper-motor-driven high-performance liquid chromatography pump, stop-and-go flow control, and anti-icing skimmer/catcher enable rapid restart without venting the vacuum. Spectral interferometry confirms jet thicknesses of 0.7 μm (ϕ 25 μm) and 1-2 μm for the standard ϕ 50 μm setup. The open design of the apparatus simplifies alignment and supports both transmission and grazing-incidence reflection modes. This apparatus provides a robust, user-friendly platform for ultrafast liquid-phase spectroscopy and surface-sensitive measurements.