No abstract

The properties of an electron beam~e-beam! formed in air under atmospheric pressure are reported. The nanosecond generators RADAN-303~two devices! and RADAN-220, producing nanosecond voltage pulses with amplitude of up to 400 kV and subnanosecond rise time were used in the experiments. It was shown for the first time that the duration of e-beam current of gas diode behind the foil does not exceed 0.1 ns. The maximum amplitude of current of a supershort avalanche electron beam~SAEB! behind the foil was ;400 A. The data on the influence of various parameters on e-beam current amplitude measured behind the foil were obtained. An electron beam with energy less than 60 keV and powerful X-ray radiation were formed in discharge gap simultaneously with SAEB.

The paper presents the results of experimental research on nanosecond high-pressure diffuse discharges in an inhomogeneous electric field with a time resolution of ∼100 ps. It is shown that decreasing the voltage pulse duration enhances the feasibility of the diffuse discharge with no additional ionization. In particular, with a narrow interelectrode gap, a diffuse discharge in atmospheric pressure air with preionization by runaway electrons, called a runaway-electron-preionized (REP) diffuse discharge (DD), was realized. It is found that most of the energy is deposited to the REP DD plasma once the voltage across the gap reaches its maximum. It is demonstrated that the REP DD holds promise for producing high-power VUV pulses. The radiation power attained with xenon at a wavelength of ∼172 nm is 8 MW. The treatment of an AlBe foil with an REP DD in atmospheric pressure air provides cleaning of its surface layer from carbon and penetration of oxygen atoms into the foil to a depth of 450 nm per 300 pulses.

This paper reports on the properties of a supershort avalanche electron beam generated in the air or other gases under atmospheric pressure and gives the analysis of a generation mechanism of supershort avalanche electron beam, as well as methods of such electron beams registration. It is reported that in the air under the pressure of 1 atm, a supershort (<100 ps) avalanche electron beam is formed in the solid angle more than 2π steradian. The electron beam has been obtained behind a 45 µm thick Al-Be foil in SF6 and Xe under the pressure of 2 atm, and in He, under the pressure of about 15 atm. It is shown that in SF6 under the high pressure (>1 atm) duration (full width at half maximum) of supershort avalanche electron beam pulse is about 150 ps.

This article reports on experimental studies of subnanosecond electron beams formed in air under atmospheric pressure. An electron beam with an amplitude of ∼170 A with a duration at FWHM of ∼0.3 ns has been obtained. Based on beam temporal characteristics and discharge spatial characteristics, the critical fields were supposed to be reached at plasma approach to anode. Simultaneously, the sharp high-energy pulse of e-beam current is generated. Of critical importance is the cathode type and occurrence on the cathode of plasma protrusions. It is shown that to get maximum amplitude of the electron beam in the gas diode, the discharge in the gas diode should be volumetric.