Dynamics and correlated performance of a photo-triggered discharge-pumped HF laser using SF6 with hydrogen or ethane

A detailed experimental study of an X-ray photo-triggered HF laser, with an active volume of 312 cm(3), has been performed in Ne/SF6/H-2 and Ne/SF6/C2 H6 mixtures. Parameters involved have been the storage line capacitance and the circuit inductance, the capacitors charging voltage, the PH-molecule t ype and partial pressure, and the X-ray dose for the preionization. High la ser performance has been achieved with C2H6: an output energy up to 3 J cor responding to a specific energy of 9.6 J/1 at an efficiency of 4.7%, which strengthens the advantage of the photo-triggering technique to energize hig h-power HF lasers. However the optimum performance achieved with H-2, 5.75 J/1 and 3.5%, are lower. It is shown, through a time-resolved study of the electrical discharge and spatial dynamics correlated to laser power and ene rgy measurements, that discharge instabilities are responsible for the poor laser performance of the mixture with H-2. These instabilities, which lead to are development, are characteristics of the discharge in Ne/SF6. It is demonstrated for the first time that addition of a heavy hydrocarbon, such as C2H6, to that mixture induces the discharge stabilization so that the la ser emission arises in a homogeneous active medium. This effect allows us t o achieve better laser performance than with H-2.