Using the X-FEL as a source to investigate photo-pumped X-ray lasers

H-like and He-like resonantly photo-pumped laser schemes were proposed for producing X-ray lasers nearly four decades ago. However, demonstrating these schemes in the laboratory has proven to be elusive. One major challenge has been the difficulty of finding an adequate resonance between a strong pump line and a line in the laser plasma that drives the laser transition. After finding a good resonance, a second challenge has been to simultaneously create the pump and laser plasma in close proximity so as to allow the pump line to transfer its energy to the laser material. With the construction of the X-ray free electron laser (X-FEL) at the SLAC Linac Coherent Light Source (LCLS) researchers now have a tunable X-ray laser source that can be used to replace the pump line in previously proposed laser schemes and allow them to study the physics and feasibility of photo-pumped laser schemes. In this paper we model the Na-pumped Ne X-ray laser scheme that was proposed and studied many years ago by replacing the Na He-α pump line at 1127 eV with the X-FEL at LCLS. We predict large gains greater than 400 cm on the 4f – 3d transition at 231 Å.