Modelling of recombination X-ray lasers

¹ Laboratoire de Spectroscopie Atomique et Ionique, CNRS and Université Paris-Sud, bât. 350, 91405 Orsay Cedex, France
² LULI: National Facility for the Use of Intense Lasers under the CNRS and Ecole Polytechnique, 91128 Palaiseau, France
³ Laboratoire de Physique des Milieux Ionisés, CNRS and Ecole Polytechnique, 91128 Palaiseau, France

Abstract

The numerical simulation of X-ray laser experiments, based on the recombination pumping scheme in laser-produced plasmas, is discussed. Modelling studies, performed in different laboratories and related to experimental results on C5+ and Al10+ ions, are presented. We then describe the model that we have developed and recently improved for lithium-like ions. The agreement between X-UV gain predictions and experimental results is discussed for two transitions in Li-like aluminium. Though the simulations correctly reproduce the main experimental features, several discrepancies, which concern in particular the absolute value of gain, are still to be removed. We have used our model to investigate the effect of a non-uniform laser illumination of the target, on the X-ray amplification. We find that these non-uniformities could affect the propagation of the amplified X-ray beamlet and lead to a very poor apparent gain. Such uncontrolled parameters of the experiment should be taken into consideration in the analysis of the experimental results and in the comparison of the latter with the modelling results. Other possible causes of discrepancy between theory and experiments are examined.