<title>Pulsed HF chemical laser using a VUV phototriggered discharge</title>

Abstract

A simple corona phototriggered discharge has been operated in SF6/C2H6/Ne mixture at typical pressures 90-110 Torr, deposited energies up to 180 J/1 and has resulted in the production of high energy HF laser pulse aroung 2.8 j.m. The maximum laser energy was 3.8 J per pulse which corresponds to a specific energy of 7 J/liter and to an efficiency of 4 % based upon the energy stored on the sustaining capacitor. Results of discharge modeling have shown that F atoms were mainly produced by electron excitation of SF6 dissociative electronic states.

The influence of and molecules on discharge equilibrium and F-atom production in a phototriggered HF laser using

“…HF lasers energized by electrical discharges have been the subject of many studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. The best laser performances, namely the maximum output energy and electrical efficiency, have been achieved using pre-ionized pulsed discharges between flat electrodes and reactive gas mixtures which contain H 2 and F 2 molecules [6,7].…”

High-power pulse and pulse-periodic nonchain HF (DF) lasers

“…Therefore in the given case it is expedient to initiate SIVD, for example, by a low-current spark located either outside the discharge gap or in a hole on the cathode [5]. In principle, this regime is similar to a "photo triggered discharge" mode [15,17,28]. However in classical "photo triggered discharge" schemes applied to excimer lasers, a powerful illumination of the gap is necessary since this illumination serves the dual function of initiating breakdown and producing the necessary primary electron number density in a gas medium.…”

“…(Regardless of lasers, SSVD can in principle be obtained in a highly nonuniform field, for instance, in the rod-plane gap.) Clearly the first condition cannot be practically met in such strongly electronegative gas as SF6 [5,7] because of great losses of primary electrons due to electron attachment except for the special "photo triggered discharge" mode [15], which, however, is ineffective for energy input into molecular gases owing to low over-voltages at the gap and, in the case of large discharge gaps and active medium volumes (large-sized electrodes), is not realized at all. On increase of the laser aperture and discharge volume, the problem also arises as to how to meet the second condition because of both technical difficulties in fabrication of large-sized intricate shape electrodes and in connection with rise of the discharge circuit inductance caused by a useless growth in the transverse sizes ofthe electrodes [3,4].…”

High energy HF (DF) lasers

“…Clearly, the irst condition cannot be observed in such a strongly electronegative gas as SF 6 [5,7] because of the great primary electron losses from electron attachment, except for in the special 'photo triggered discharge' mode [15], which, however, is ineffective for energy input into molecular gases because of the low over-voltages at the gap and, in the case of large discharge gaps and active medium volumes, it is not realized at all. With increasing laser aperture and discharge volume, the problem of how to meet the second condition also arises-there are tech nical dif iculties regarding the fabrication of large-sized intricate-shaped electrodes and the rise of the discharge circuit inductance caused by a useless growth in the trans verse size of the electrodes [3,4].…”

“…Therefore, in the given case, it is expedient to initiate SIVD by, for example, a low-current spark located either outside the discharge gap or in a hole on the cathode [5]. In principle, this regime is similar to a 'photo triggered discharge' mode [15,17,27]. However, in classical photo trig gered discharge schemes being applied to excimer lasers, a powerful illumination of the gap is necessary, since this illu mination serves the dual function of initiating the breakdown and producing the necessary primary electron number density in a gas medium.…”