Soft x-ray spectral radiations from Xe, H2O, and CO2 cryogenic targets irradiated by a 1 μm neodymium doped YAG-slab laser at pulse widths of 12–20 ns and at laser intensities of 5×1010–1012 W/cm2 have been observed. These targets radiate soft x-rays in a wavelength range of 10–13 nm which is useful for projection microlithography. We have found a strong x-ray spectral peak at λ = 10.8 nm with a Xe cryogenic target. The measured x-ray conversion efficiency with the Xe target was 0.8%/sr(λ=10.8±0.27 nm) at a laser intensity of 1×1012 W/cm2. This was ten times or more efficient than that with H2O and CO2 targets. © 1998 American Institute of Physics.