A review of Ni-like X-ray laser experiments undertaken using the VULCAN laser at the Rutherford Appleton Laboratory

Recent progress using the VULCAN laser at the Rutherford Appleton Laborator y to pump X-ray lasing in nickel-like ions is reviewed. Double pulse pumpin g with similar to 100 ps pulses has been shown to produce significantly gre ater X-ray laser output than single pulses of duration 0.1-1 ns. With doubl e pulse pumping, the main pumping pulse interacts with a pre-formed plasma created by a pre-pulse. The efficiency of lasing increases as there is a re duced effect of refraction of the X-ray laser beam due to smaller density g radients and larger gain volumes, which enable propagation of the X-ray las er beam along the full length of the target. The record shortest wavelength saturated laser at 5.9 nm has been achieved in Ni-like dysprosium using do uble pulse pumping of 75 ps duration from the VULCAN laser. A variant of th e double pulse pumping using a single similar to 100 ps laser pulse and a s uperimposed short similar to 1 ps pulse has been found to further increase the efficiency of lasing by reducing the effects of over-ionisation during the gain period. The record shortest wavelength saturated laser pumped by a short similar to 1 ps pulse has been achieved in Ni-like samarium using th e VULCAN laser operating in chirped pulse amplified (CPA) mode. Ni-like sam arium lases at 7.3 nm. (C) 2000 Academie des sciences/Editions scientifique s et medicales Elsevier SAS.