Progress towards demonstration of soft x-ray amplification at shorter x-ray wavelengths

Recent progress in soft x-ray laser research has been marked by significant advances in source development and x-ray laser applications. In the first area, efforts have focused on producing amplification at higher powers and shorter wavelengths. The push to shorter wavelength is closely related to efforts to demonstrate significant applications, as the utility of techniques such as x-ray laser holography l is enhanced when performed with radiation in the "water window" between the K absorption edges of carbon (43.76 Å) and oxygen (23.32 Å). In this paper, we report on recent results aimed at demonstrating gain at shorter wavelengths. The first selection will discuss measurements of amplification in Ni-like ions, where amplification has been shown at wavelengths as short as 50.26 Å in Ni-like Yb. This is 6.5 Å away from the water window threshold at 43.76 Å. We also discuss results from recent recombination experiments. These schemes have been investigated because of their possible higher efficiency due to rapid scaling to shorter wavelength with ion charge Z.