Tabletop Soft X-Ray Laser for Magnetic Imaging at Transition Metal M Edges

X-ray magnetic circular dichroism and linear dichroism are important tools in probing and imaging magnetic materials. The short wavelengths of the soft X-ray regime provide enhanced spatial resolution compared to visible wavelengths, and unique atomic absorption spectra allow for element specific measurements. Soft X-ray experiments are often conducted at large synchrotron facilities. More recently, high-harmonic generation setups have allowed tabletop access but with limited photon flux. We are developing a third complimentary tool that provides the advantages of tabletop access of high-harmonic generation along with the single shot capabilities of synchrotron facilities. We have developed a compact soft X-ray laser driven by an all diode-pumped 1030 nm Yb:YAG joule level laser. The Yb:YAG laser beam is split into two arms which are both focused onto overlapping 5 mm x 30 um lines on a metal target. A long pulse arm is used to generate a plasma, and a short picosecond pulse arm to rapidly heat the plasma creating a population inversion and amplification in soft X-ray transitions of Ni-like ions. We have demonstrated soft X-ray lasing in transitions of Ni-like molybdenum, niobium, and zirconium at wavelengths of 18.9, 20.3, and 22.0 nm respectively, chosen for optimal magnetic dichroism in nickel, cobalt, and iron