Computational modelling of short pulse X-ray laser experiments

The basic theory of amplified spontaneous emission (ASE) for long lived las ers was developed several years ago, allowing a clear understanding of the effects of saturation on the output irradiance to be achieved. The developm ent of ultra-short lasers has necessitated the development of the model to include time dependence. Extending a simple ASE model developed earlier, we have investigated in detail the features of time dependent ASE laser actio n. The model is compared to more detailed computational simulation, and sho ws good agreement, whilst revealing the limitations of the model, Simulatio n shows that the beam is broadened transverse to the propagation direction. Good agreement is shown between simulation and experimental values.