Demonstration of soft x-ray laser of Ne-like Ar at 69.8nm pumped by capillary discharge

The demonstration of a 69.8nm laser on 3p ³P₂ ? 3s ¹P₁ (J = 2 ? 1) transition of Ne-like Ar pumped by capillary discharge is reported in this Letter. A main current of 12 kA with rise time of 43 ns was chosen to generate the plasma in a 35cm long capillary filling with pressure of Ar as low as 11 Pa, resulting in a gain coefficient of 0.34cm^?1 and gain-length product of 11 at 69.8nm. Also observed is a weak laser on 3p ³D₂ ? 3s ³P₁ (J = 2 ? 1) transition of Ne-like Ar at 72.6nm in the same condition. In addition, multiwavelength lasing at 46.9, 69.8, and 72:6nm was simultaneously realized in a capillary discharge plasma column, conditioning the pressure of Ar to 13 Pa.