Prepulse-produced plasma waveguide for longitudinally pumped nickellike molybdenum x-ray lasers

A novel method is proposed by which multiple prepulses are used to generate a waveguidelike density profile for longitudinally pumped transient collisional excitation x-ray lasers. It is shown that a high-density waveguide with subcritical densities can be produced with this method, which requires a typical total prepulse energy of only 200 mJ. A multipulse pumping configuration to achieve the optimal plasma condition and also to completely confine the longitudinal pump beam within the waveguide is proposed. Gain calculations along the waveguide reveal the conditions necessary for saturated operation of the 18.9-nm nickellike molybdenum x-ray laser.