V. S. Skakun

On formation of subnanosecond electron beams in air under atmospheric pressure

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.

Capacitive and barrier discharge excilamps and their applications (Review)

The results of studies, development works, and tests of barrier-and capacitive-discharge excilamps radiating in the UV and VUV spectrum regions are presented. The main information on the designs of radiators and generators is presented. The spectral, temporal, and energy characteristics of excilamps based on the emission of KrCl*, XeCl*, XeI*, XeBr*, KrBr*, Xe*2, Br*2, and Cl*2 molecules and the I* atomic line are described. It is shown that the created generators and sealed-off radiators have long service lives. Examples of specific applications of excilamps are presented.

Phenomenon of apokamp discharge

A new phenomenon has been discovered where a bend of a plasma channel becomes of a source of one or several diffuse jets that have a length (at a given voltage) up to 4–6 cm and are directed across the plasma channel at a pulse-periodic spark discharge in air under normal conditions. The phenomenon is called apokamp discharge (apokamp). The spectrum of radiation of the apokamp includes primarily the bands of electron-vibrational transitions of the second positive system of molecular nitrogen. The conditions of the formation of apokamp have been experimentally revealed and it has been established that it consists of plasma bunches moving from the plasma channel at each pulse at a velocity of about 220 km/s.

Source of an atmospheric-pressure plasma jet formed in air or nitrogen under barrier discharge excitation

We analyzed the atmospheric pressure plasma jet excited in air and nitrogen by a barrier discharge. The source forming stable plasma jets of length up to 4 cm in air and nitrogen is constructed, and its energy and spectral characteristics are measured.

Excilamp producing up to 130 W of output power and possibility of its applications

Results of an experimental study of a coaxial exciplex lamp pumped by glow discharge are presented. An average power of radiation in the wavelength region below 250 nm and as high as about 130 W has been achieved. Efficiency of the excilamp operation based on input power of 14% was demonstrated. The possibility of applications of this excilamp is discussed.

Optical characteristics of the plasma of a nanosecond atmospheric-pressure volume discharge in a nonuniform electric field

Optical characteristics of the plasma of nanosecond volume discharges in air, nitrogen, krypton, argon, neon, and Ar/N2 and Ar/Xe mixtures at elevated pressures are investigated. The discharges are excited in a gap with a cathode of small curvature radius. The waveforms and spectra of plasma emission from discharges in different gases in the 230-to 600-nm spectral range are measured. Optical generation in an Ar/Xe mixture is achieved at an active length of 1.5 cm. A comparison is performed of the spectral characteristics of the emission from nitrogen, krypton, argon, and neon excited by a volume discharge in a nonuniform electric field, by a nanosecond electron beam, and by a pulsed volume discharge in a uniform electric field at a high initial voltage.

Sealed efficient excilamps excited by a capacitive discharge

The development of sealed XeCl (λ∼308 nm), KrCl (λ∼222 nm), and XeI (λ∼253 nm) excilamps excited by a capacitive rf discharge is reported. It is shown that highly efficient emission of exciplex molecules is achieved under capacitive discharge excitation and the emitter has a simple design. An average emission power of 3W was obtained with a ∼12% efficiency and the lifetime of the sealed excilamps was longer than 1000 h.

A windowless VUV excilamp

An open windowless excilamp capable of operating on argon (λ ∼ 126 nm), krypton (∼146 nm), and xenon (∼172 nm) dimers is described. The lamp has a total radiating surface area of 23 × 23 = 529 cm2. At a total power of ∼0.8 W radiated through this area, the average output power density at λ ∼ 126 nm is ∼1.6 mW/cm2 at a distance of 2 cm from the emitting surface. A pulsed discharge between insulator-coated anode and thin wire cathode ensures a high efficiency of the proposed radiation source operating in the vacuum ultraviolet spectral range.

Capacitive Discharge Excilamps

Investigation was made ofthe characteristics ofXeCl (λ ~ 308 nm), KrC1 (λ ~ 222 nm) and Xci (λ ~ 253 nm) capacitive discharge excilamps. High efficiency of exciplex molecules and simple design have been obtained under capacitive HF discharge excitation. Cylindrical excilamps with radiation output through side surface ofthe cylinder and through one or two windows placed on the tube ends have been developed. High UV radiation power and electrical power deposition to fluorescence conversion resulted in efficiencies of up to 12%. The study of XeC1, KrCl and XeI excilamps have shown, that it is possible to create sealed-off samples with lifetime more than 1000 hours. The stability of output parameters ofthe capacitive discharge excilamps is studied and the mechanism of chlorine losses in low pressure halogencontaimng excilamps made of quartz was determined. The possibility of creation of capacitive discharge excilamps with short pulse duration was studied. In capacitive discharge cylindrical KrClexcilamp, at λ~222 nm the radiation pulse power up to 2.5 kW was obtained. Powerful radiation pulses 50 ns in duration were obtained at pulse repetition rate of 1 kHz.

Emission properties of apokamp discharge at atmospheric pressure in air, argon, and helium

Emission spectra of the plasma jet of apokamp discharge in air, helium, and argon are studied. Apokamp at atmospheric pressure is formed in the areas of strengthening of the electric field near the bends in the channel of the pulse-periodic discharge and is directed perpendicularly to the discharge channel. Apokamp consists of a bright narrow “appendage” connected with the discharge channel and with the diffuse jet emerging from the channel. It is shown that, in helium, the emission of the diffuse part of apokamp is dominated by N2 and N2+, while emission of the “appendage” display lines and bands of He, N2, N2+, O, and OH. In argon, emission spectra of the diffuse part of the plasma jets contain not only N2 and N2+, but also Ar lines. It is assumed that the surrounding air plays an important role in the formation of the diffuse part of apokamp in helium and argon.