Influence of current prepulse on capillary-discharge extreme-ultraviolet laser

In this paper the influence of the prepulse current on a capillary-discharge 46.9 nm Ne-like Ar extreme-ultraviolet laser is reported. A current pulse with a typical RC shape (decay time of similar to 30 mu s) was used as a prepulse. Measurements indicate that when the filling pressure is low, the output can be improved by reducing the time delay between the application of the prepulse current and the onset of the main discharge current. For high pressure the reverse is true. This change is most significant for time delays between 2 and 4 mu s, and beyond these time delays, the effect is less significant. This effect is attributed to the changes in the capillary channel pressure and also to the absorption of the laser emission by the plasma plume ejected during the prepulse. Thus, apart from ensuring a minimal amount of prepulse current to prevent nonuniformity effects, the timing of the application of the prepulse current is also important.