Full characterization of a high-gain saturated x-ray laser at 13.9 nm

We report the characterization of a saturated collisional Ni-like Ag soft-x-ray laser at 13.9 nm. A main pumping pulse of 140 J in 100 ps [Formula Presented] the preceded 3 ns before by a prepulse of variable intensity was used to create the amplifying medium. The target length was varied up to 2 cm for the single target and 4 cm for the double target. For the double target the quasi-traveling-wave excitation (QTWE) technique has been used. Time-integrated as well as time-resolved measurement of the [Formula Presented] [Formula Presented] line have been performed for different pumping configurations and target geometry. Due to the very high pumping intensity and the resulting plasma overheating, an exceptionally high-gain coefficient of [Formula Presented] has been measured leading to the saturation regime for plasma length longer than 8 mm. Time-resolved and time-integrated [Formula Presented] spectra of the plasma are also displayed and ionization balance is discussed. Using double-target geometry a narrow divergence is observed due to efficient coupling factor as well as a temporal increase of the x-ray laser pulse duration in the direction of QTWE. The far-field pattern of the x-ray laser beam has been characterized. Two vertically separated bright spots were observed for the double target, while a single spot was observed for the single target. The energy of the double-target x-ray laser beam has been measured to be [Formula Presented] which closely corresponds to an output power of 5 MW.