Yu. K. Kurilenkov

Inertial electrostatic confinement and DD fusion at interelectrode media of nanosecond vacuum discharge. PIC simulations and experiment

The generation of energetic ions and DD neutrons from microfusion at the interelectrode space of a low-energy nanosecond vacuum discharge has been demonstrated recently [1, 2]. However, the physics of fusion processes and some results regarding the neutron yield from the database accumulated were poorly understood. The present work presents a detailed particle-in-cell (PIC) simulation of the discharge experimental conditions using a fully electrodynamic code. The dynamics of all charge particles was reconstructed in time and anode–cathode (AC) space. The principal role of a virtual cathode (VC) and the corresponding single and double potential wells formed in the interelectrode space are recognized. The calculated depth of the quasistationary potential well (PW) of the VC is about 50–60 keV, and the D+ ions being trapped by this well accelerate up to energy values needed to provide collisional DD nuclear synthesis. The correlation between the calculated potential well structures (and dynamics) and the neutron yield observed is discussed. In particular, ions in the potential well undergo high-frequency (~80 MHz) harmonic oscillations accompanied by a corresponding regime of oscillatory neutron yield. Both experiment and PIC simulations illustrate favorable scaling of the fusion power density for the chosen IECF scheme based on nanosecond vacuum discharge.

Skin effect and reflectivity in strongly coupled plasmas

The skin depth and the Fresnel reflectivity are evaluated in the case of strongly coupled plasmas. Analysis is based on the explicit expression for the dynamic collision frequency. Peculiarities of electromagnetic wave penetration into collision‐dominated plasmas and reflectivity in the vicinity of critical density are considered.

Spectra of dense pure hydrogen plasma in Balmer area

Abstract We study experimentally the pure dense hydrogen plasma spectra in Balmer area. Dense plasma with electron concentrations up to ≈10 19 cm −3 has been created by pulse discharge in quartz capillary. Diagnostics of the plasma is made on the basis of optical measurements at λ=632.8 nm . The temperature profile is defined from independent measurements of brightness and transparency at different distances from the centre of the capillary. Detailed study is performed for two discharge conditions: at electron density N e =6.5×10 18 cm −3 and temperature T=18000 K and N e ≈1.5×10 19 cm −3 , T=23000 K . The self-consistent scheme to calculate the weakly nonideal plasma spectra based on the microfield model and unperturbed oscillator strengths distribution is also described. For the lower density regime we have obtained a satisfactory agreement of measured spectra with calculated ones. For higher electron density the lowering of experimental spectra was obtained near Balmer series limit in comparison with calculations. Further measurements at higher electron densities (N e >10 19 cm −3 ) are required to prove the obtained tendency for some “clearing up” of dense hydrogen plasma spectra at Balmer area.

Radiative continua of noble gas plasmas

Abstract A simple completely analytical method for the calculation of the plasma radiation continuum in the visible and neighbouring regions is derived. It is based on the semi-classical quantum defect theory. In spite of the simplicity the accuracy of the method is found to be comparable with those of Schluter and Hofsaess calculations, but its main advantage is the reasonable description of the plasma density (weak coupling) effects in the near-threshold region. Thus, our calculation does not show the sharp threshold of the photoionization continuum and a correct comparison with experiment in the whole wavelength range under consideration can be made. A good agreement with experimental data on the continuous radiation of neon, argon, krypton and xenon plasmas is found. The calculation scheme presented may be useful for moderately dense plasma diagnostics and looks as reasonable basis for incorporation of strong coupling effects.

On high frequency electrical conductivity of strongly coupled plasma

High frequency electrical conductivity is studied in the case of a strongly coupled quasiclassical plasma. Analytic results are derived both from the memory function formalism and the linear response theory developed earlier. The results obtained are compared with computer simulation data. Collective effects are shown to play an important role in optical properties of collision dominated plasmas.

Hard X-ray bursts and DD microfusion neutrons from complex plasmas of vacuum discharge

We create the random complex media of high-power density in low-energy nanosecond vacuum discharges. Hard X-ray emission efficiency, generation of energetic ions (∼1 MeV) and neutrons, trapping and releasing of fast ions and/or X-rays from interelectrode aerosol ensembles are the subject of our study. The neutrons from DD microfusion, as well as the modelling of some interstellar nuclear burning due to microexplosive nucleosynthesis are discussed. The value of neutron yield from DD fusion in interelectrode space varies and amounts to ∼105–107/4π per shot under ≈ 1 J of total energy deposited to create all discharge processes

Free-free Light Absorption in Strongly Coupled Plasmas

The light absorption coefficient is evaluated in strongly coupled plasmas. Analysis is based on the calculation of the dynamic collision frequency of electron-ion scattering. Under plasma conditions when electron scattering has quantum character, the Born approximation for screened electron-ion interaction is used. In the case of classical scattering non Born corrections become essential at high frequencies. Interpolation formulas for the collision frequency and Gaunt factor are presented at intermediate frequencies. Theoretical calculations are compared with measurements of bremsstrahlung for dense Ar and Al plasmas and computer simulation data.

Neutron yield and Lawson criterion for plasma with inertial electrostatic confinement

The physics of plasma formation is discussed in the systems with inertial electrostatic confinement (IEC) during the convergent to the axis of cylindrical geometry of the ion flow accelerated periodically in the field of virtual cathode, which is formed by the injected electrons. The ranges of plasma parameters and the resulting neutron yield are determined for different modes of ion flux formation. The requirements are formulated to the technical parameters of the system with IEC to create both a powerful neutron source with a rate of generation exceeding 1010-1012 particles/s and to achieve a positive energy output (analogue of Lawson criterion).

Optical spectra of hydrogen plasma at electron concentrations above 1019 cm−3

The optical spectra of a dense (nonideal) plasma formed in a pulsed discharge in a closed quartz capillary were studied. The emission spectra of pure hydrogen plasma at a temperature of 23000 K and an electron concentration of ∼1.5×1019 cm−3, twice the value achieved earlier, were obtained. The plasma diagnostics was carried out by spectroscopic methods taking into account the radial inhomogeneity of the plasma column. The spectral intensity measured in the Balmer region (300–800 nm) was found to be lower than that calculated by the model of weakly nonideal plasma, an effect not observed at lower densities. Possible reasons for the discrepancy between the experiment and the calculation were considered. One of them being the specific density effect of a relative rise in plasma transmission with increasing density.

Radiation continuum of dense krypton plasma

Available experimental data on the continuum radiation in the visible spectrum of dense krypton plasmas are considered and compared with calculations. Variations of the continuum spectra with the plasma density are examined. For the calculation of weakly non-ideal plasmas spectra a simple analytical method based on semiclassical quantum defect theory is presented. It takes into account the shift and smoothing of the photoionization thresholds resulting from the influence of the statistical plasma quasistatic microfields on the higher atomic levels. For the experiment and theory are in close general agreement, while for theory tends to overestimate the experimental plasma absorption (emission) data. General features of density effects in plasma radiation and the possible breakdown of the isolated atom picture are discussed.