Visualization of double-pulse discharge in excimer laser with gas flow

The double-pulse discharge has been demonstrated in a gas flow with a veloc ity of 200 m/s which is generated by a Ludwieg tube. A gas mixture of heliu m and argon is used to simulate the excitation discharge of excimer lasers. The shock waves and the gas density perturbation between two successive di scharges have also been visualized applying the shadowgraph technique using a high-speed image-converter camera. The second discharge at an equivalent pulse repetition frequency (f) of 10 kHz becomes an are through the heated column which is generated by the first discharge. At f = 5 kHz, the glow d ischarge can be produced between the electrodes, however, an are is also ob served through the heated column which is located somewhat downstream of th e electrodes. Only a glow discharge is possible up to f = 3 kHz. These resu lts clearly demonstrate that the heated column has a decisive effect on the stability of repetitive pulse discharges.