An unambiguous correspondence between the potential of an insulated metal target, irradiated by a continuous electron beam, and secondary electron emission yield from the target, in the medium vacuum pressure range (at fore-vacuum pressures), is demonstrated. This connection allows one to estimate the secondary emission properties of the target material and to predict the beam-plasma parameters. Moreover, this can help to estimate the intensity and energy of the ion bombardment of the target when it is irradiated by the electron beam. The metallic target potential value was found to be dependent on its material (aluminum, stainless steel, titanium and copper), which is related to the secondary emission properties of the surface. Since an electrically insulated metal target can be regarded as an experimental model for exploring the effect of energetic electron beam bombardment of dielectric surfaces, this work also provides a firm basis for the study of electron-beam modification of dielectric materials. A method for estimation of the potential of a dielectric having a secondary emission yield less than 1 and irradiated by a dc electron beam in fore-vacuum pressures is proposed. This method is based on measurements of the ionic sheath length and plasma parameters near the surface of the target irradiated by the electron beam.
Results of experimental study of nanosecond diffuse discharge in SF 6 and gas mixtures of SF 6 with H 2 , D 2 and C 2 H 6 are presented. The aim of this work is to study parameters of discharge between two extended electrodes with a small radius of curvature in SF 6 and SF 6 with additives. It was shown that diffuse discharge can be formed in SF 6 at elevated pressure between blade electrodes with length of 30 cm. It was also confirmed that in a sharply non-uniform electric field a beam of runaway electrons is generated and that the gap breakdown occurs due to ionisation waves which begin on electrodes with small radius of curvature. Laser action in the infrared spectral region was obtained in SF 6-H 2 (D 2 , C 2 H 6) mixtures. The laser output up to 110 mJ was easily achieved which corresponds to ultimate intrinsic efficiency (with respect to deposited energy) of 10%.
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