High gain‐production efficiency and large brightness X‐UV laser at Palaiseau

A large gain has been measured for the J=0–1 line of neonlike Zn at λ=21.2 nm. The time evolutions and the localization of emission zones of the J=0–1 and J=2−1 lines are compared. It is shown that a train of very small prepulses before the main pulse has an important role in the J=0=1 emission. A half‐cavity has been successfully used to attain a nearly saturated intensity with a 2 cm long plasma. The X‐UV pulse energy is of 400 μJ, the laser power of 5 MW. The driving laser is the 0.4 KJ, 600 ps laser of LULI.