Formation of sub-μm x-ray beam from tabletop soft x-ray laser

An x-ray microprobe with a sub-micron size beam and high intensity has been obtained by focusing the x-ray laser output for the first time. In our experiment, an x-ray laser of Li-like Al 3d-4f transition at 15.47 nm was delivered from an unstable cavity consisting of a concave mirror, a flat mirror with a square orifice of 100 mu m x 100 mu m The beam from the orifice was then focused by using a Schwarzschild mirror coated with Mo/Si multilayers. The x-ray beam size with a diameter less than 0.5 mu m and the estimated photon number of about 2 x 10(6) photons/shot into the spot were achieved.