S. V. Golubev

A point-like source of extreme ultraviolet radiation based on a discharge in a non-uniform gas flow, sustained by powerful gyrotron radiation of terahertz frequency band

The possibility and prospects of extreme ultraviolet (UV) point-like source development are discussed in the present paper. The UV source is based on the discharge sustained by powerful gyrotron radiation of terahertz (THz) frequency band in non-uniform gas flow injected into vacuum volume through a nozzle with diameter less than 1 mm. Recent developments of THz-band gyrotrons with appropriate power level made such discharges possible. First experimental results on a point-like plasma creation by 100 kW radiation of 0.67 THz gyrotron are presented. The possibility of discharge localization within the area less than 1 mm is demonstrated. The discharge emission within the wavelength range from 112 nm to 650 nm was studied. The measured power of light emission in the range of 112–180 nm was measured to be up to 10 kW.

Formation of multi-charged ions and plasma stability at quasigasdynamic plasma confinement in a mirror magnetic trap

It is known that an increase in plasma density in sources of multicharged ions leads to a substantial increase of ion current and slightly improves the ion distribution over charge states. The validity of this statement was verified in experiments with plasma densities not exceeding several units of 1012 cm−3. In the present work it is demonstrated experimentally that, for the electron densities exceeding 1013 cm−3, the regime of plasma confinement in a trap changes significantly and the quasigasdynamic regime of plasma confinement is realized. Comparison of numerical simulations and experimental data showed the essential influence of the anisotropy of electron velocity distribution in a plasma on the ion charge state distribution. This allows looking for the optimal conditions for the creation of highly charged ions in plasma. In this article we also address problems of plasma stability in an axisymmetric mirror trap under powerful microwave pumping. First experiments on ion extraction from a dense plasm...

Multiple ionization of metal ions by ECR heating of electrons in vacuum arc plasmas

A joint research and development effort has been initiated, whose ultimate goal is the enhancement of the mean ion charge states in vacuum arc metal plasmas by a combination of a vacuum arc discharge and electron cyclotron resonance (ECR) heating. Metal plasma was generated by a special vacuum arc mini-gun. Plasma was pumped by high frequency gyrotron-generated microwave radiation. The results have demonstrated substantial multiple ionization of metal ions. For a lead plasma, ECR heating increased the maximum attainable ion charge state from Pb2+ up to Pb6+. The confinement parameter was as high as ∼109 cm−3 s. Further increase of the ion charge states will be attained by increasing the vacuum arc plasma density and optimizing the ECR heating conditions.

Observation of pulsed fast electron precipitations and the cyclotron generation mechanism of burst activity in a decaying ECR discharge plasma

We have detected and investigated quasi-periodic series of pulsed energetic electron precipitations in the decaying plasma of a pulsed ECR discharge in a mirror axisymmetric magnetic trap. The observed particle ejections from the trap are interpreted as the result of resonant interaction between energetic electrons and a slow extraordinary wave propagating in the rarefied plasma across the external magnetic field. We have been able to explain the generation mechanism of the sequences of pulsed precipitations at the nonlinear instability growth phase in terms of a cyclotron maser model in which the instability threshold is exceeded through a reduction in electromagnetic energy losses characteristic of the plasma decay.

High current density ion beam formation from plasma of electron cyclotron resonance discharge

This article describes the research effort to obtain a quality ion beam with high currents from the dense plasma of the pulsed electron cyclotron resonance discharge pumped with high-power millimeter-wave radiation. The results of the experiments aimed at optimization of the two-electrode system for ion extraction are presented. Under the conditions, when the density of the ion current in the vicinity of the plasma electrode was 65–75 mA/cm2, the normalized emittance of the ion beam did not exceed 0.19 π mm mrad.

High current density production of multicharged ions with ECR plasma heated by gyrotron transmitter

In order to study the possibilities to produce high currents of pulsed heavy ion beams dedicated to synchrotron injection, two new approaches of ECR devices are now underway. The basic principle consists in maintaining a functioning point of the source with the highest density as possible and a minimum confinement time for the production of a given charge state. It means that for a constant neτi product we try to maximize ne and minimize τi. For this purpose two experiments are in progress at ISN/Grenoblea and IAP/Nizhny Novgorod.b The first one consists of using a minimum |B| magnetic structure with a 1.8 mirror ratio characteristic value with a 28 GHz frequency injection. In this case we explore different functioning points up to 10 kW of UHF power. The second one consists of a simple mirror magnetic system (simple mirror ion source, SMIS) working at 37.5 GHz with a mirror ratio up to 3 (2.5 T) where we study discharges with a peak power up to 100 kW. We will show that, in spite of a very short rising t...

Laboratory study of kinetic instabilities in a nonequilibrium mirror-confined plasma

Kinetic instabilities of nonequilibrium plasma heated by powerful radiation of gyrotron in electron cyclotron resonance conditions and confined in a mirror magnetic trap are reported. Instabilities are manifested as the generation of short pulses of electromagnetic radiation accompanied by precipitation of hot electrons from magnetic trap. Measuring electromagnetic field with high temporal resolution allowed to observe various dynamic spectra of electromagnetic radiation related to at least five types of kinetic instabilities. This paper may be of interest in the context of a laboratory modeling of nonstationary wave-particle interaction processes in nonequilibrium space plasma since the observed phenomena have much in common with similar processes occurring in the magnetosphere of the Earth, planets, and in solar coronal loops.

Generation of multiply charged refractory metals in an electron-cyclotron resonant discharge in a direct magnetic trap

The possibility of additional ionization of refractory metal ions in the vacuum arc plasma injected to a magnetic trap due to additional heating of electrons by microwave radiation under the conditions of electron-cyclotron resonance is demonstrated. High-power short-wave radiation of gyrotrons used in experiment makes it possible to work with a higher (on the order of 1013 cm−3) density of the plasma and to ensure the confinement parameter at a level of 3 × 108 cm−3 s at an electron temperature sufficient for multiple ionization.

Maser based on cyclotron resonance in a decaying plasma

The features of generating electromagnetic radiation in a two-level cyclotron maser whose active medium is a decaying nonequilibrium plasma confined in a magnetic field with the mirror configuration have been examined. It has been shown that, even in the absence of a continuously acting source of nonequilibrium particles (inversion of the medium), the system can exhibit the regimes of the quasimonochromatic or pulse generation of radiation owing to a fast monotonic decrease in the instability threshold that is characteristic of the plasma decay. The theory is confirmed by the results of observations of the burst activity of the decaying pulsed-discharge plasma under the conditions of the electron cyclotron resonance in the direct axisymmetric magnetic trap.

Features of plasma glow in low pressure terahertz gas discharge

Investigations of the low pressure (1–100 Torr) gas discharge in the powerful (1 kW) quasi-optical terahertz (0.55 THz) wave beams were made. An intense afterglow was observed after the end of gyrotron terahertz radiation pulse. Afterglow duration significantly exceeded radiation pulse length (8 μs). This phenomenon could be explained by the strong dependence of the collisional-radiative recombination rate (that is supposed to be the most likely mechanism of electron losses from the low pressure terahertz gas discharge) on electron temperature.