ABSTRACT
In order to meet the requirements of practical applications, the improvement of spatial coherence of X-ray lasers has become an important subject in the collision excitation research after the achievement of saturated output. It is difficult to build a resonant cavity for improving the X-ray laser quality. Recently, Shiji Wang, et al did the travelling wave amplification experiments. A soft X-ray laser with nearly saturated intensity and minimum divergence angle ~ 1 mrad was obtained. In this paper, we analyse these experiments. We simulate the X-ray laser propagation in the plasma with an exponential electron density distribution, finding that there are waveguide phenomena. Using these we can design a good quality amplifier.
