Multi-millijoule, highly coherent X-ray laser at 21 nm as a routine tool for applications

A recently developed double-pass, deeply saturated Ne-like Zn X-ray laser at 21.2 nm, is presented. The system consists of a 3-cm long plasma and a half cavity constituted by a flat multilayer mirror located at 8.5 mm. The pump sequence includes a weak prepulse and a main heating pulse, delivering ∼500 J of net energy at 1.315 μm, in pulses with a length of ∼450 ps. A novel prepulse illumination geometry is employed, in which the prepulse beam generates a wide preplasma buffer into which subsequently a much more tightly focused main beam is coupled. The emitted X-ray beam is narrowly collimated and possesses a remarkably high spatial quality. In the half-cavity regime, the system provides an output energy of about 4 mJ, corresponding to peak power of 40 MW. A fully routine operation of the half-cavity has been achieved, making it possible to perform, without any realignment or manual intervention, about 100 shots with one multilayer mirror