Detailed simulations of Ne-like Cu x-ray laser are undertaken using the EHYBRID code. The atomic physics data are obtained using the Cowan code. The optimization calculations are performed in terms of the intensity of background and the time separation between the background and the short pulse. The optimum value is obtained for the conditions of a Nd: glass laser with 1.2 ps pulse at 4.4 × 1015 W cm−2 irradiance pumping a plasma pre-formed by a 280 ps duration pulse at 5.4 × 1012 W cm−2 with peak-to-peak pulse separation set at 300 ps. X-ray resonance lines between 6 Å and 15 Å emitted from copper plasmas have been simulated. Free-free and free-bound emission from the Si−, Al−, Mg−, Na−, Ne− and F−like ions is calculated in the simulation.