On the time of lasing onset and the end-effect of a soft x-ray laser device using a capillary z-pinch discharge

We have measured the time of lasing onset of a capillary z-pinch discharge used for Ne-like Ar soft x-ray laser generation. It was found that for a relatively long plasma, the relationship between the time of lasing onset and the filling pressure of the Ar gas agrees, in trend, with that predicted by simulation. An interesting result was observed: the time of lasing onset becomes delayed when the length of the capillary becomes shorter, which is considered to be caused by an end-effect of the capillary on the pinching process. This also implies that a relatively long capillary is favourable for obtaining a plasma column of uniformity, and thus for reducing the relative absorption of laser power.