We report the demonstration of x-ray lasing in nickel-like tin at 12 n
m by using the prepulse technique in combination with a curved target.
A gain length of 4.8 was obtained with a 3-cm-long target of 1 m radi
us of curvature irradiated by the Asterix iodine laser at 1.315 mu m w
ith a total energy of 500 J and a 7.5% prepulse.