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This paper is devoted to discussing the technical characteristics of pulsed plasma-focus (PF) generators and their features as fusion reactors as an alternative for stationary thermonuclear install...

Бұл жұмыста магнит өрісінің газдық разряд плазмасындағы тозаңды бөлшектердің зарядталу процестеріне әсері зерттелді. Магнит өрісінің қатысуымен тозаңды бөлшектердің зарядталу процестерін зерттеу бойынша газдық разряд плазмасына тән параметрлерге арналған есептеулер сандық түрде ұяшықтағы бөлшектер және Монте-Карло әдістері негізінде жүргізілді. Зарядтың мәні, тозаңды бөлшектердің зарядталу уақыты, сондай-ақ магнит өрісінің әр түрлі мәндерінде электрондар мен иондардың тығыздығының радиалды таралуы алынды. Магнит өрісін ескеру тозаңды бөлшек зарядының абсолюттік мәнінің азаюына және тозаңды бөлшектерің зарядталу уақытының ұлғаюына әкелді. Бұл магниттік өрістің күштік сызықтары бойымен плазма бөлшектерінің траекториясының шектелуі есебінен тозаң бөлшектерінің зарядының төмендеуін көрсетеді.

The effect of an external magnetic field on the dust particle charging in gas discharge plasmas has been studied using the particle-in-cell and Monte Carlo methods at 1, 2, and 4 T. This paper presents the results for the dust particle charge and the characteristic dust particle charging time for different values of the magnetic field induction. Our simulations have shown that the external magnetic field reduces the absolute value of the dust particle charge and extends the characteristic charging time. In addition, the number density of electrons and ions decreases in the vicinity of the dust particle due to the magnetic force, which we interpret as the action of the external magnetic field hampering plasma flow to the surface of the charged dust particle. To visualize this effect, we show the trajectories of the electrons and ions around the dust particle at different values of the magnetic field induction.

We present the experimental results on influence of an external magnetic field on the dust particles which were suspended in the strata of a glow discharge, where the magnetic field was created using a Helmholtz coil. Observations were made in the strata that located between the coils, under the coil, and above the coil. We observed an interesting behavior of dust particles, which was not previously reported. It was revealed that the dust structure rotates clockwise above the coil and counterclockwise under the coil, while the dust structure located between the coils does not rotate. Experiments were performed with both mono- and poly-disperse dust particles at $B \le 28$ mT. The radial distribution of the angular velocity of dust particles, at the induction of the magnetic field 8, 13, and 19 mT, in different regions was measured. For explanation of the experimental results, we developed a simple theoretical model which shows that the direction of the rotation is determined by the radial component of the magnetic field induction.

Recently, it was shown that the neutral shadowing interaction can be significantly stronger in the cryogenic complex plasma than in the plasma with neutrals at room temperature. Here, we present the results of the investigation—by molecular dynamics (MD) simulations—of the impact of the neutral shadowing interaction on the radial pair distribution function and the velocity autocorrelation function (VAF) of the charged dust particles in a 2-D layer. The spectrum of VAF was computed to estimate the influence of the neutral shadowing force on the oscillations of dust particles. We found that the neutral shadowing interaction can significantly affect the structural properties and the characteristic longitudinal oscillation frequency of dust particles if the characteristic radius of the neutral shadowing interaction exceeds a mean interdust particle distance. The latter case corresponds to low pressures, $p Pa, and cryogenic temperatures less than 10 K. In addition, the dust acoustic wave taking into account that the neutral shadowing force was derived. It is found that the neutral shadowing force leads to the increase of the sound speed of the dust acoustic wave.

We have considered basic theoretical models describing various aspects of the formation and acceleration of plasma in pulsed accelerators. The discharge current, magnetic field, and plasma bunch velocity have been determined experimentally at different initial gas pressures in the accelerator chamber. We have considered the correspondence of some theoretical models of plasma acceleration to experimental data obtained in a KPU-30 coaxial accelerator. It is shown that the formation of the plasma in the coaxial accelerator depends on the plasma density, and acceleration processes at densities higher and lower than a certain transient density value on the order of 1011–1012 cm–3 are different. At a density higher than this critical value, the plasma is accelerated by a magnetic force. At the same time, at a low plasma density, plasma can be accelerated by an internal electric field.

This paper reports on the molecular dynamics simulations of classical two-dimensional (2D) electric dipole systems. The properties of 2D systems with bare (nonscreened) and screened dipole-dipole interactions have been investigated. Based on the polygon construction method, we present simulation results on the phase transition, and we locate the melting and freezing points of 2D dipole systems in terms of a polygon disorder parameter, with the polygon disorder parameter being the sum of nontriangular polygon order parameters. It was found that the phase transition of the system occurs when the polygon disorder parameter has a value 0.165. This result was cross-checked by using both local and overall orientational order parameters. We also identified that the value of the average local orientational order parameter at the phase transition point is 0.67. These results are valid for the ordinary (bare) dipole-dipole interaction as well as the screened dipole-dipole interaction, and they are expected to be general for other 2D systems with repulsive pair interaction. We observed that both melting and freezing points shift to lower values of temperature due to screening. In the liquid state, the radial distribution function and polygon construction method show the loss of order in a structure as screening becomes more severe. Furthermore, the impact of screening on the system's collective excitation spectra and diffusive characteristics at liquid and solid states has been studied. Results show the decrease in the values of both longitudinal and transverse sound speeds and the emergence of anomalous superdiffusive motion in the liquid state due to screening.

Surface waves propagating in the semi-bounded collisional hot QCD medium (quark-gluon plasma) are considered. To investigate the effect of collisions as damping and non-ideality factor, the longitudinal and transverse dielectric functions of the quark-gluon plasma are used within the Bhatnagar-Gross-Krook (BGK) approach. The results were obtained both analytically and numerically in the long wavelength limit. First of all, collisions lead to smaller values of surface wave frequency and their stronger damping. Secondly, the results show that non-ideality leads to the appearance of a new branch of surface waves compared to the collisionless case. The relevance of the surface excitations (waves) for the QGP realized in experiments is discussed., 10 pages, 2 figures, revised version accepted for publication in Phys. Part. Nucl. Letters

We investigate the energy-loss characteristics of an ion in warm dense matter (WDM) and dense plasmas concentrating on the influence of electronic correlations. The basis for our analysis is a recently developed ab initio quantum Monte Carlo- (QMC) based machine learning representation of the static local field correction (LFC) [Dornheim et al., J. Chem. Phys. 151, 194104 (2019)JCPSA60021-960610.1063/1.5123013], which provides an accurate description of the dynamical density response function of the electron gas at the considered parameters. We focus on the polarization-induced stopping power due to free electrons, the friction function, and the straggling rate. In addition, we compute the friction coefficient which constitutes a key quantity for the adequate Langevin dynamics simulation of ions. Considering typical experimental WDM parameters with partially degenerate electrons, we find that the friction coefficient is of the order of γ/ω_{pi}=0.01, where ω_{pi} is the ionic plasma frequency. This analysis is performed by comparing QMC-based data to results from the random-phase approximation (RPA), the Mermin dielectric function, and the Singwi-Tosi-Land-Sjolander (STLS) approximation. It is revealed that the widely used relaxation time approximation (Mermin dielectric function) has severe limitations regarding the description of the energy loss of ions in a correlated partially degenerate electrons gas. Moreover, by comparing QMC-based data with the results obtained using STLS, we find that the ion energy-loss properties are not sensitive to the inaccuracy of the static local field correction (LFC) at large wave numbers, k/k_{F}>2 (with k_{F} being the Fermi wave number), but that a correct description of the static LFC at k/k_{F}≲1.5 is important.

Dense Plasma Focus machine may be suitable for fusion first wall studies and its related material researches. As is well-known plasma focus devices are sources of high energy ions, electrons, x-rays and neutrons and intense bursts of fast plasma streams. In this paper, experimental measurements of neutron emission and hard x-ray emission from the plasma focus device are presented. The measurement of neutron and hard x-ray emission is studied using silver activation counter detector with two different dimensions Pb shielding and two scintillator photomultiplier detector systems. The research paper reported that the experimentally detected neutron emission in the radial direction where focus occurs also evaluated neutron fluency at different distances. The results show that neutron emission with different intensities and pulse width. Silver detector registered neutrons in the range 106-107 n/shot in the radial direction. The maximum neutron yield is 1.7×107 neutrons per shot. Key words: neutron yield, plasma focus, X-ray, shielding, silver foil, photo multiplier tube.

The relaxation of temperature, coupling parameters, the excess part of equation of state, and the correlation energy of the non-isothermal hot dense plasmas are considered on the basis of the method of effective interaction potentials. The electron–ion effective interaction potential for the hot dense plasma is discussed. The accuracy of description of the dense plasma properties by the effective electron–ion interaction potential is demonstrated by the agreement of the derived quantities like stopping power and transport coefficients calculated using our methodology with the results of the finite-temperature Kohn-Sham density-functional theory molecular dynamics, and orbital-free molecular dynamics results as well as with the data obtained using other theoretical approaches. Keywords: Dense plasma, Effective potentials, Temperature relaxation, Stopping power, Transport, PACS codes: 52.65.−y, 52.25.Dg, 52.27.Gr, 52.25.Kn

Motivated by experiments on the generation of streaming plasmas in high energy density facilities,industrial setups, and fundamental dusty plasma research, the plasma polarization around a test charge instreaming plasmas is considered in this work. The induced charge density distribution of the plasmaconstituents is discussed for the subsonic, sonic, and supersonic regime taking into account the non-Maxwellian distribution of the flowing ions. It is shown that the plasma polarization (the plasmawakefield) in the vicinity of the test charge shows different scaling in the subsonic and supersonicregimes, where Mach number is defined as the ratio of the ion streaming velocity and the ion soundspeed. In contrast to the wake potential, the density decays strongly monotonically in the plasma wakeand does not exhibit an oscillatory pattern or trailing maxima. Therefore, the picture of an ion focusingeffect creating a separated ion region downstream was not confirmed.

From the static polarization function of electrons in the random phase approximation, the quantum Bohm potential for the quantum hydrodynamic description of electrons and the density gradient correction to the Thomas–Fermi free energy at a finite temperature for the two- and one-dimensional cases are derived. The behaviour of the Bohm potential and of the density gradient correction as a function of the degeneracy parameter is discussed. Based on recent developments in the fluid description of quantum plasmas, the Bohm potential for the high-frequency domain is presented.

The dynamical structure factor (DSF) of strongly coupled ions in dense plasmas with partially and strongly degenerate electrons is investigated. The main focus is on the impact of electronic correlations (non-ideality) on the ionic DSF. The latter is computed by carrying out molecular dynamics (MD) simulations with a screened ion-ion interaction potential. The electronic screening is taken into account by invoking the Singwi-Tosi-Land-Sj\"olander approximation, and compared to the MD simulation data obtained considering the electronic screening in the random phase approximation and using the Yukawa potential. %This allows us to gain insight into the impact of the electronic non-ideality on the ionic DSF. We find that electronic correlations lead to lower values of the ion-acoustic mode frequencies and to an extension of the applicability limit with respect to the wave-number of a hydrodynamic description. Moreover, we show that even in the limit of weak electronic coupling, electronic correlations have a non-negligible impact on the ionic longitudinal sound speed. Additionally, the applicability of the Yukawa potential with an adjustable screening parameter is discussed, which will be of interest, e.g., for the interpretation of experimental results for the ionic DSF of dense plasmas.

Present work presents calculations and experimental studies on the formation and dynamics of plasma onthe “plasma focus” set up. Physical conditions were determined and critical parameters were calculatedfor estimating the neutron yield for kilojoule and megajoule set ups. The results of plasma diagnostics andflow formation in the CPA-30 and PF-4 set ups are also shown. A comparison of calculated data andexperimental values is performed. The value of the neutron yield parameter is justified and the possiblecause of the appearance of saturation is indicated. The rationale for the development of further research inthe direction of creating conditions for thermonuclear fusion in installations of the plasma focus type isgiven. The neutron flux was observed on high-voltage gas discharges with a specific geometry of theelectrodes. The result of measuring the anisotropy of the neutron yield along the axial z and radial φdirections was equal to Yn(z)/Yn(φ)~ 2 ÷ 3, which contradicts the thermonuclear mechanism.

The response of the uniform electron gas (UEG) to an external perturbation is of paramount importance for many applications. Recently, highly accurate results for the static density response function and the corresponding local field correction have been provided both for warm dense matter [J. Chem. Phys. 151, 194 104 (2019)] and strongly coupled electron liquid [Phys. Rev. B 101, 045 129 (2020)] conditions based on exact ab initio path integral Monte Carlo (PIMC) simulations. In the present work, we further complete our current description of the UEG by exploring the high energy density regime, which is relevant for, e.g. astrophysical applications and inertial confinement fusion experiments. To this end, we present extensive new PIMC results for the static density response in the range of 0.05 ≤ r s ≤ 0.5 and 0.85 ≤ θ ≤ 8. These data are subsequently used to benchmark the accuracy of the widely used random phase approximation and the dielectric theory by Singwi, Tosi, Land, and Sjölander (STLS). Moreover, we compare our results to configuration PIMC data where they are available and find perfect agreement with a relative accuracy of 0.001 − 0.01%. All PIMC data are available online.

In the present work, classical electron–ion scattering, Coulomb logarithm, and stopping power are studied taking into account the quantum mechanical diffraction effect and the dynamic screening effect separately and together. The inclusion of the quantum diffraction effect is realized at the same level as the well-known first-order gradient correction in the extended Thomas–Fermi theory. In order to take the effect of dynamic screening into account, the model suggested by Grabowski et al. in 2013 is used. Scattering as well as stopping power of the external electron (ion) beam by plasma ions (electrons) and scattering of the plasma's own electrons (ions) by plasma ions (electrons) are considered differently. In the first case, it is found that in the limit of the non-ideal plasma with a plasma parameter Γ → 1, the effects of quantum diffraction and dynamic screening partially compensate each other. In the second case, the dynamic screening enlarges scattering cross-section, Coulomb logarithm, and stopping power, whereas the quantum diffraction reduces their values. Comparisons with the results of other theoretical methods and computer simulations indicate that the model used in this work gives a good description of the stopping power for projectile velocities $v\,{\rm \lesssim}\, 1.5 v_{{\rm th}}$, where vth is the thermal velocity of the plasma electrons.

The effective electron (proton)-He and electron (proton)-He+ screened pair interaction potentials arising as a result of partial screening of the helium nucleus field by bound electrons, taking into account both screening by free charged particles and quantum diffraction effect in dense plasmas were derived. The impact of quantum effects on screening was analyzed. It was shown that plasma polarization around the atom leads to the additional repulsion (attraction) between the electron (proton) and the helium atom. The method of constructing the full electron (proton)-He and electron (proton)-He+ screened pair interaction potentials as the sum of the derived potentials with the polarization potential and exchange potential is discussed. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Dust particle layers are routinely established in radio-frequency plasmas, where their levitation height is defined by the balance of forces acting on the particles. Here, based on particle-in-cell simulations, we demonstrate the effect of excitation waveform on this levitation height, by using harmonic and alternating-phase waveforms that may as well include an additional dc component. We also demonstrate that the dust charge can be tuned by the properties of the excitation waveform and suggest that the dust component of the plasma can be heated through a variation of the excitation waveforms via a mechanism similar to second-order Fermi acceleration.

The ion potential in the warm dense matter regime exhibits wake effects due to streaming degenerate electrons and has been discussed previously [Phys. Rev. E 91, 023102 (2015)]. Here, we extend the analysis with particular focus on anomalous wake effects that is (i) the collision-induced wake amplification, and (ii) the non-monotonic temperature dependence of the wake amplitude. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The collision of a polarizable neutral particle with a charged particle in plasmas is studied. The neutral particle interaction with a charged particle is considered to be due to an induced dipole moment. Taking into account screening and a finite size of colliding particles, we present accurate and simple interpolation formulas for the total scattering cross section in the case of contact of the neutral particle with the dust particle surface. The results are obtained for both weak and strong coupling between colliding particles.

Dusty white dwarfs are natural objects for studying the properties of cosmic dusty plasmas. We present the results of computation of the charge, radius, and temperature of a carbon dust particle in the atmosphere of dusty white dwarf G29-38, which is a typical example of a dusty white dwarf. The calculation results show that dust particles life-time in the atmospheres of dusty white dwarfs is of the order of microsecond. Therefore, dust particles cannot be sustained in a typical white dwarf atmosphere.

The structural properties of strongly coupled ions in dense plasmas with moderately to strongly degenerate electrons are investigated in the framework of the one-component plasma model of ions interacting through a screened pair interaction potential. Special focus is put on the description of the electronic screening in the Singwi-Tosi-Land-Sjoelander (STLS) approximation. Different crosschecks and analyses using ion potentials obtained from ground-state quantum Monte Carlo data, the random phase approximation (RPA), and existing analytical models are presented for the computation of the structural properties, such as the pair distribution and the static structure factor, of strongly coupled ions. The results are highly sensitive to the features of the screened pair interaction potential. This effect is particularly visible in the static structure factor. The applicability range of the screened potential computed from STLS is identified in terms of density and temperature of the electrons. It is demonstrated that at r_s > 1, where rs is the ratio of the mean inter-electronic distance to the Bohr radius, electronic correlations beyond RPA have a non-negligible effect on the structural properties. Additionally, the applicability of the hypernetted chain approximation for the calculation of the structural properties using the screened pair interaction potential is analyzed employing the effective coupling parameter approach.

In this paper the relaxation properties of non-isothermal dense plasmas were studied. Based on the effective interaction potentials between particles, the Coulomb logarithm for two-temperature non-isothermal dense plasmas was obtained. These potentials take into consideration long-range multi-particle screening effects and short-range quantum-mechanical effects in two-temperature plasmas. The relaxation processes in such plasmas were studied using the Coulomb logarithm. The obtained results were compared with theoretical works of other authors and with the results of molecular dynamics simulation. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Wakefields are of omnipresent nature in non-equilibrium situations, but their appearance and parametrical scaling is very diverse. Therefore, in this work the topological structure and characteristics of the dynamically screened potential is outlined for three representative systems in completely different physical regimes: (i) a classical complex (dusty) plasma, (ii) a degenerate electron-ion plasma at high densities, and (iii) an ultrarelativistic quark-gluon plasma. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

In order to obtain the dynamical collision frequency and the dynamical conductivity, we used the molecular dynamics simulation of dense two-component plasmas with the pair interaction potential of charged particles taking into account quantum-mechanical effects.The temperature range of 10^4 K < T < 10^8 K and the density range of 10^21 cm^-3 < n

Today, the efforts of scientists to solve problems of fusion associated mainly with magnetic systems, primarily with tokamaks and etc. One of alternative method is a plasma focus (PF) installations, based on the focusing of the plasma beam in a small area with high density. There are same works published last time in which considered this problem, but it wasn't many. We mention the works [1] and [2], where attempts have been made to obtain fusion processes in PF devices. As shoved Niculin [3], increasing of discharge current of PF more than 2 MA haven't been to proportionality increase of plasma density. There is known, that in coaxial guns appear a Hall Effect, which decreased a plasma velocity [4]. If we exclude this phenomenon from plasma, there is possible to increase the energy of plasma particles. But the ways of plasma description, based on average energy 3kT/2 is not suitable for PF devices, as well as Lawson criteria. For these devices the target theory is more applicable. So, we are apology, that not only power, but geometry of experiment play important role. On this way, we have made experiments on basic of pulsed plasma accelerator CPA-30 with short and long electrodes. The experiments showed a significant dependence of the flux focusing parameters on the electrode geometry. Analysis of experiments and calculations show, that the efficiency of plasma compression became much higher with a short electrode. However, as the length of the electrode decreases, no increase in the plasma temperature is observed. The reason for this is the too long discharge time, so the accelerated particles in the plasma can be thermal. To start the synthesis and emission of X-rays from the focus region, calculations show that discharge times on the order of picoseconds are necessary.

The screened ion potential in non-ideal dense quantum plasmas is investigated by invoking the Singwi-Tosi-Land-Sj\"olander approximation for the electronic local field correction at densities $r_s\lesssim 2$ and degeneracy parameters $\theta\lesssim 1$, where $r_s$ is the ratio of the mean inter-particle distance to the first Bohr radius, and $\theta$ is the ratio of the thermal energy to the Fermi energy of the electrons. Various cross-checks with ion potentials obtained from ground state quantum Monte-Carlo data, the random phase approximation, as well as with existing analytical models are presented. Further, the importance of the electronic correlation effects for the dynamics in strongly coupled ionic subsystems for $0.1\leq r_s\leq 2$ is discussed.

In this paper we present a software package based on modern information technologies that allows rapid analysis and visualization of the properties of complex plasmas. The properties of plasma are simulated by two means. First of all, we have applied the molecular dynamics simulation method which numerically solves the equations of motions for plasma particles. Secondly, we calculate microscopic properties of plasma by using the Boltzmann equation with additional relations, initial and boundary conditions.

In the present work two component dense semiclassical plasma of protons and electrons is considered. Microscopic and electrodynamic properties of the plasma by molecular dynamic simulation are investigated. For these purposes semiclassical interparticle potential which takes into account quantum mechanical diffraction and symmetry effects is used. The considered range of density of plasma is n = 1022cm−3 to n = 1024cm−3. Fluctuations and dynamic dielectric functions were calculated using velocity autocorrelation functions.

In this paper, the multipole expansion method is used to determine effective interaction potentials between particles in both classical dusty plasma and dense quantum plasma. In particular, formulas for interactions of dipole-dipole and charge-dipole pairs in a classical nondegenerate plasma as well as in degenerate quantum and semiclassical plasmas were derived. The potentials describe interactions between atoms, atoms and charged particles, dust particles in the complex plasma, atoms and electrons in the degenerate plasma, and metals. Correctness of the results obtained from the multipole expansion is confirmed by their agreement with the results based on other methods of statistical physics and dielectric response function. It is shown that the method of multipole expansion can be used to derive effective interaction potentials of compound particles, if the effect of the medium on the potential of individual particles comprising compound particles is known.

In this work the semiclassical potential for plasma particles pair interactions, which takes into account the diffraction effects due to the uncertainty principle in two-component plasma (the region of temperatures 104K < T < 108K and densities 1021cm–3 < n ≤ 1024cm–3), was proposed. The values of this potential were numerically calculated and an interpolation formula was obtained (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Interaction between dusty particles remains to be an interesting issue that still requires deeper theoretical and experimental investigations. In the present paper we formulate a theoretical approach to the calculation of effective interaction potential of dust particles on the basis of Poisson equation and experimentally measured pair correlation functions. By application of our model to the data from the liquid phase of dust formations in stratified dc glow discharge, it is shown that there is an attractive component in the interaction of dust particle (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Beginning from the semiclassical Hamiltonian, the Fermi pressure and Bohm potential for the quantum hydrodynamics application (QHD) at finite temperature are consistently derived in the framework of the local density approximation with the first order density gradient correction. Previously known results are revised and improved with a clear description of the underlying approximations. A fully non-local Bohm potential, which goes beyond of all previous results and is linked to the electron polarization function in the random phase approximation, for the QHD model is presented. The dynamic QHD exchange correlation potential is introduced in the framework of local field corrections, and considered for the case of the relaxation time approximation. Finally, the range of applicability of the QHD is discussed.

In this article a dense nonideal, nonisothermal plasma is considered. New effective screened interaction potentials taking into account quantum-mechanical diffraction and symmetry effects have been obtained. The effective potential of the ion-ion interaction in plasmas with a strongly coupled ion subsystem and semiclassical electron subsystem is presented. Based on the obtained effective potentials the analytical expressions for internal energy and the pressure of the considered plasma were obtained.

The screened interaction potential between two compound particles, compound particle and charged particle (ion or electron) in multipole approximation for simulation of nonequilibrium warm dense matter are discussed. The density and temperature range has been considered at which the formalism of compound particles can be used. It is proposed that the presented screened potential can be useful for the simulation of the heavy ions in the presence of streaming electrons. Discussions about the implication of a compound particle picture for consideration of the dynamics of the beam of the charged particles in plasmas are given. The proposed model of interaction between heavy ions consists of dipole terms and the short range repulsion due to the Pauli exclusion principle.