High gain x-ray lasers at the water window.

Abstract

We propose a scheme for producing a spatial and temporal averaged gain of 45 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ in nickel-like Ta, including refraction. This result is achieved by irradiating a 40 \ensuremath{\mu}g/${\mathrm{cm}}^{2}$ target with a low intensity pulse [2\ensuremath{\omega}(\ensuremath{\lambda}=0.53 \ensuremath{\mu}m), 5\ifmmode\times\else\texttimes\fi{}${10}^{13}$ W/${\mathrm{cm}}^{2}$, 80 ps] to make the plasma subcritical. This is followed by a high intensity pulse (2\ensuremath{\omega}, 2\ifmmode\times\else\texttimes\fi{}${10}^{15}$, 20 ps) to give the proper ionization. Therefore the principle of pulse shaping to achieve high gain using high intensity pump radiation is demonstrated.