This article surveys our present understanding of the internal structure of the fully developed quark-gluon plasma at temperatures outside the crossover region. The theoretical part of the review covers perturbative and nonperturbative approaches to quark-gluon plasma structure, in particular, hard-thermal loop effective theory, lattice QCD and the functional renormalization group. The phenomenological part of the review scrutinizes the information that has been derived from bulk observables and hard probes in relativistic heavy ion collisions in terms of how it informs our knowledge about the structure of the quark-gluon plasma. The final section lists possible avenues for future progress.
Time-dependent, predictive simulations were performed with the 1.5D tokamak integrated modeling code TRANSP on a large set of well-analyzed, high performing discharges from the National Spherical Torus Experiment (NSTX) in order to evaluate how well modern reduced transport models can reproduce experimentally observed temperature profiles in spherical tokamaks. Overall, it is found that simulations using the Multi-Mode Model (MMM) more consistently agree with the NSTX observations than those using the Trapped Gyro-Landau Fluid (TGLF) model, despite TGLF requiring orders of magnitude greater computational cost. When considering all examined discharges, MMM has median overpredictions of electron temperature ($T_e$) and ion temperature ($T_i$) profiles of 28% and 27%, respectively, relative to the experiment. TGLF overpredicts $T_e$ by 46%, with much larger variance than MMM, and underpredicts $T_i$ by 25%. As $β$ is increased across NSTX discharges, TGLF predicts lower $T_e$ and significant flattening of the $T_i$ profile, conflicting with NSTX observations. When using an electrostatic version of TGLF, both $T_e$ and $T_i$ are substantially overpredicted, underscoring the importance of electromagnetic turbulence in the high $β$ spherical tokamak regime. Additionally, calculations with neural net surrogate models for TGLF were performed outside of TRANSP with a time slice flux matching transport solver, finding better agreement with experiment than the TRANSP simulations, highlighting the impact of different transport solvers and simulation techniques. Altogether, the reasonable agreement with experiment of temperature profiles predicted by MMM motivates a more detailed examination of the sensitivities of the TRANSP simulations with MMM to different NSTX plasma regimes in a companion paper, in preparation for self-consistent, time-dependent predictive modeling of NSTX-U scenarios.
Time-dependent kinetic models are ubiquitous in computational science and engineering. The underlying integro-differential equations in these models are high-dimensional, comprised of a six--dimensional phase space, making simulations of such phenomena extremely expensive. In this article we demonstrate that in many situations, the solution to kinetics problems lives on a low dimensional manifold that can be described by a low-rank matrix or tensor approximation. We then review the recent development of so-called low-rank methods that evolve the solution on this manifold. The two classes of methods we review are the dynamical low-rank (DLR) method, which derives differential equations for the low-rank factors, and a Step-and-Truncate (SAT) approach, which projects the solution onto the low-rank representation after each time step. Thorough discussions of time integrators, tensor decompositions, and method properties such as structure preservation and computational efficiency are included. We further show examples of low-rank methods as applied to particle transport and plasma dynamics.
The use of heat pipes (HP) for the DEMO in-vessel plasma-facing components (PFCs) has been considered because of their high capacity to transport the heat from a heat source to a heat sink by means of the vaporization and condensation of the working fluid inside and their ability to enlarge the heat transfer area of the cooling circuit substantially. Recent engineering studies conducted in the framework of the EUROfusion work package Divertor (Wen et al, 2021) indicate that it is possible to design a heat pipe with a capillary limit above 6 kW using a composite capillary structure (wherein axial grooves cover the adiabatic zone and the condenser, and sintered porous material covers the evaporator). This power level would correspond to an applied heat flux of 20 MW/m2, rendering such a design interesting with respect to a divertor target concept. To validate the results of the initial engineering analysis, several experiments have been conducted to evaluate the actual performance of the proposed heat pipe concept. The present contribution presents the experiment’s results regarding the examination of the operating limits of two different designs for an evaporator: one featuring a plain porous structure, and one featuring ribs and channels.
Goal. Receipt and analysis of close analytical correlations for the engineering calculation of maximal temperature of Tm and pressures of Pm in a plasma channel, time of tex explosion of explorer, active resistance of Rc and specific conductivity of γp of plasma channel, to entered in explorer Wi and selected in the channel of Wc of thermal energy and high speed of vmw distribution of shock acoustic wave in the plasma products of electric explosion (EE) in gas of explorer under the action of large impulsive current (LIC). Methodology. Basis of thermophysics, thermodynamics, theoretical and applied electrical engineering, electrophysics bases of technique of high-voltage and large impulsive currents, basis of heavy-current electronics, theory of explosion and plasma, measuring technique and electromagnetic compatibility. Results . Close formulas are got for the analytical calculation of temperature of Tm and pressures of Pm in a plasma channel, time of tex explosion of explorer, active resistance of Rc and specific conductivity of γp of plasma channel, to entered in explorer Wi and selected in the channel of Wc of thermal energy and speed of vmw of shock acoustic wave in «metallic plasma» at EE in gas of explorer, testing action LIC in the discharge chain of high-voltage generator of impulsive currents (GIC) with the stocked energy of W0. It is rotined that at EE in atmospheric air of copper explorer long 110 mm and by a radius 0,1 mm in the bit chain of GIC of the microsecond temporal range (Imc≈−190 кА; tmc≈42 μs; ωc≈26,18·103 s-1; W0≈121,4 кJ) levels of temperature of Tm, to time of tex explosion, pressures of Pm and speeds of vmw in the area of his explosion can arrive at numeral values: Tm≈121,6·103 K, tex≈3,32 μs; Pm≈14,19·109 Pa and vmw≈4693 m/s. The ways of receipt are formulated in the bit chain of GIC of «record» (most) values of temperature of Tm, pressures of Pm and speeds of vmw. It is set that at EE in atmospheric air of the indicated short thin copper explorer the coefficient of the useful use of ηc of electric energy of W0 of condenser battery of GIC arrives at the numeral value of ηc≈(Wi+Wc)/W0≈0,326 (32,6 %). Arising up in the plasma channel of discharge, initiated EE in gas of explorer, temperature of Tm and pressure of Pm, time of tex explosion of explorer, specific conductivity of γp of channel, thermal energy of Wc and speed of vmw of shock acoustic wave selected in a channel in «metallic plasma» can be certain experimental a way on results decoding of oscillograms of discharge current of ic(t) and high-voltage of uc(t) on an explorer in the chain of GIC. A formula is resulted for the close calculation of critical integral of current of Jk at EE in gas of explorers from different metals. Executed on powerful GIC heavy-current experiments were confirmed by substantive provisions offered approach near the analytical calculation of basic parameters of electro-explosive process for the probed explorer. Originality. Offered and the engineering going is scientifically grounded near the analytical calculation of the indicated thermophysical, gasodynamic and electroenergy parameters of Tm, Pm, tex, Rc, γp, Wi, Wc and vmw at EE in gas of metallic explorer, plugged in the discharge chain of GIC. Practical value. Application in electrophysics practice of the offered engineering going near a calculation in the chain of GIC of basic parameters of electro-explosive process will allow to facilitate labour of workers of scientific laboratories and promote efficiency of work of technicians-and-engineers during practical realization by them different electro-explosive technologies.
The growing significance of rare earth elements (REEs) in advanced electronic technologies and the nuclear industry, coupled with concerns about geopolitical dynamics and supply market vulnerabilities, has reignited global interest in securing domestic and economically viable sources of REEs through dedicated research and developmental pursuits. Bauxite, a naturally occurring mineral primarily composed of aluminum, has been identified to harbor an abundance of sought-after rare earth minerals, thereby rendering it a promising unconventional reservoir of REEs contingent upon geological and mineralogical characteristics. Nigeria, endowed with substantial bauxite deposits prominently situated in Ondo and Ekiti states, stands to offer an intriguing avenue for exploration. In this study, the utilization of inductively coupled plasma mass spectrometry (ICP-MS) facilitated the quantification of trace elements within samples obtained from six distinct production sites spanning Ondo and Ekiti states in Nigeria. The aim was to elucidate correlations between multi-elemental REE compositions and geographical origins. Employing both single quadrupole (SQ) and multi-collection sector field (MS) modes, concentrations of Pb, Cd, As, Zn, Mn, Al, Ca, Ni, K, Na, Mg, Cu, Fe, Ti, P, Cr, and Si were rigorously determined. Remarkably, ICP-MS analysis consistently revealed a palladium (Pd) concentration of 228.05 ppb across all sampled materials, factoring in a dilution factor of 175x. Consequently, the actual concentration of the digested solution was established at 39.91 ppm mg/L. The outcomes of this investigation hold potential significance in categorizing Nigerian bauxite deposits as viable REE sources, as well as in engineering tailored techniques to efficiently recover these elements. Such findings harbor promising economic prospects for the nation, positioning the solid mineral sector as a pivotal driver of Nigeria's burgeoning economy.
Partial discharge (PD) in the void cavity inside the insulation of the high-voltage (HV) cable is one of the critical problems. This article describes an approach to investigate the spatial distribution of plasma species related to PD dynamics in an ellipsoid void. The plasma dynamics of this type of discharge has been simulated using a self-consistent 2-D model. The ellipsoid void has the longest diameter of 1.5 mm and the shortest diameter of 0.4 mm and it is located at 6.8 mm from the center of the HV. The results show that there are two current pulses during each cycle of the applied voltage. The current pulses were obtained at the ends of the ellipse. The results of the spatial distribution for the charged species showing that both O2+ and O− are a dominated species. The simulation results revealed, in later PD processes, the N2+ and O− start to concentrate at the concave surface of the ellipsoid ends of the void.
Magnetic reconnection, a plasma process converting magnetic energy to particle kinetic energy, is often invoked to explain magnetic energy releases powering high-energy flares in astrophysical sources including pulsar wind nebulae and black hole jets. Reconnection is usually seen as the (essentially 2D) nonlinear evolution of the tearing instability disrupting a thin current sheet. To test how this process operates in 3D, we conduct a comprehensive particle-in-cell simulation study comparing 2D and 3D evolution of long, thin current sheets in moderately-magnetized, collisionless, relativistically-hot electron-positron plasma, and find dramatic differences. We first systematically characterize this process in 2D, where classic, hierarchical plasmoid-chain reconnection determines energy release, and explore a wide range of initial configurations, guide magnetic field strengths, and system sizes. We then show that 3D simulations of similar configurations exhibit a diversity of behaviours, including some where energy release is determined by the nonlinear relativistic drift-kink instability. Thus, 3D current-sheet evolution is not always fundamentally classical reconnection with perturbing 3D effects, but, rather, a complex interplay of multiple linear and nonlinear instabilities whose relative importance depends sensitively on the ambient plasma, minor configuration details, and even stochastic events. It often yields slower but longer-lasting and ultimately greater magnetic energy release than in 2D. Intriguingly, nonthermal particle acceleration is astonishingly robust, depending on the upstream magnetization and guide field, but otherwise yielding similar particle energy spectra in 2D and 3D. Though the variety of underlying current-sheet behaviours is interesting, the similarities in overall energy release and particle spectra may be more remarkable.
The theory of magnetohydrodynamic (MHD) turbulence predicts that Alfvénic and slow-mode-like compressive fluctuations are energetically decoupled at small scales in the inertial range. The partition of energy between these fluctuations determines the nature of dissipation, which, in many astrophysical systems, happens on scales where plasma is collisionless. However, when the magnetorotational instability (MRI) drives the turbulence, it is difficult to resolve numerically the scale at which both types of fluctuations start to be decoupled because the MRI energy injection occurs in a broad range of wavenumbers, and both types of fluctuations are usually expected to be coupled even at relatively small scales. In this study, we focus on collisional MRI turbulence threaded by a near-azimuthal mean magnetic field, which is naturally produced by the differential rotation of a disc. We show that, in such a case, the decoupling scales are reachable using a reduced MHD model that includes differential-rotation effects. In our reduced MHD model, the Alfvénic and compressive fluctuations are coupled only through the linear terms that are proportional to the angular velocity of the accretion disc. We numerically solve for the turbulence in this model and show that the Alfvénic and compressive fluctuations are decoupled at the small scales of our simulations as the nonlinear energy transfer dominates the linear coupling below the MRI-injection scale. In the decoupling scales, the energy flux of compressive fluctuations contained in the small scales is almost double that of Alfvénic fluctuations. Finally, we discuss the application of this result to prescriptions of ion-to-electron heating ratio in hot accretion flows.
A method of random forcing with a constant power input for two-dimensional gyrokinetic turbulence simulations is developed for the study of stationary plasma turbulence. The property that the forcing term injects the energy at a constant rate enables to set up turbulence in the desired range and to quantitatively assess energy dissipation channels in a statistically steady state. Using the developed method, turbulences in the large scale fluid and small scale kinetic regimes are demonstrated, where the theoretically predicted scaling laws are successfully reproduced.
Gaining access to the cell interior is fundamental for many applications, such as electrical recording and drug and biomolecular delivery. A very promising technique consists of culturing cells on micro-/nanopillars. The tight adhesion and high local deformation of cells in contact with nanostructures can promote the permeabilization of lipids at the plasma membrane, providing access to the internal compartment. However, there is still much experimental controversy regarding when and how the intracellular environment is targeted and the role of the geometry and interactions with surfaces. Consequently, we investigated, by coarse-grained molecular dynamics simulations of the cell membrane, the mechanical properties of the lipid bilayer under high strain and bending conditions. We found out that a high curvature of the lipid bilayer dramatically lowers the traction force necessary to achieve membrane rupture. Afterward, we experimentally studied the permeabilization rate of the cell membrane by pillars with comparable aspect ratios but different sharpness values at the edges. The experimental data support the simulation results: even pillars with diameters in the micron range may cause local membrane disruption when their edges are sufficiently sharp. Therefore, the permeabilization likelihood is connected to the local geometric features of the pillars rather than diameter or aspect ratio. The present study can also provide significant contributions to the design of three-dimensional biointerfaces for tissue engineering and cellular growth.
Acoustic solitons obtained through a reductive perturbation scheme are normally governed by a Korteweg-de Vries (KdV) equation. In multispecies plasmas at critical compositions the coefficient of the quadratic nonlinearity vanishes. Extending the analytic treatment then leads to a modified KdV (mKdV) equation, which is characterized by a cubic nonlinearity and is even in the electrostatic potential. The mKdV equation admits solitons having opposite electrostatic polarities, in contrast to KdV solitons which can only be of one polarity at a time. A Hirota formalism has been used to derive the two-soliton solution. That solution covers not only the interaction of same-polarity solitons but also the collision of compressive and rarefactive solitons. For the visualisation of the solutions, the focus is on the details of the interaction region. A novel and detailed discussion is included of typical electric field signatures that are often observed in ionospheric and magnetospheric plasmas. It is argued that these signatures can be attributed to solitons and their interactions. As such, they have received little attention.
Spectral densities of plasma fluctuations are calculated for the thermal case using classical molecular dynamics (MD) assuming Coulomb interactions and a short-range cutoff radius. The aim of the calculation is to verify limits and performances of such calculations in the light of possible generalizations, e.g. collisional or non-ideal plasmas. Results are presented for ideal, collisionless, fully ionized thermal plasmas. Comparison with the analytical theory reveals a generally satisfactory agreement with possibility for improvement when more strict numerical parameters are used albeit with a strong increase in computational cost. The largest deviations have been observed in the vicinity of the weakly damped eigenmodes. The agreement is strong in other parts of the spectrum, where Landau damping is prominent, and overcomes the effects stemming from the excess collisionality and coupling as well as from the exclusion of short-range collisions.
Purpose. Implementation of calculation estimation of such basic power descriptions of the system is a «storm cloud - earth», as total charge of q Σ , electric potential of φ r , electric energy of W 0 and amplitude-temporal parameters (ATP) of pulse current i L ( t ) in the channel of a long air spark discharge of cloud on earth. Methodology. Electrophysics bases of technique of high voltages and large currents, theoretical bases of the electrical engineering, theoretical electrophysics, theory of the electromagnetic field and technique of the strong electric and magnetic fields. Results. The results of calculation estimation of basic power descriptions are resulted in the overhigh voltage electrophysics calculation system a «storm cloud – earth». To such descriptions of a storm cloud behave: total electric charge of q Σ , concentrated in a storm cloud of spherical form of the set volume with the shallow dispersible negatively charged including as particulate dielectric matters the set by an middle closeness; electric potential of φ r is in the spherical volume of a storm cloud of the set size; electric energy of W 0 , accumulated in the spherical volume of a storm cloud of the set radius of R 0 ; PTP (amplitude of I mL and duration of τ p at level 0.5I mL ) of aperiodic impulse of current i L ( t ) of linear lightning in the plasma channel of a long air spark digit of a storm cloud on earth. The ground of possibility of the use is given in close practical calculations in place of the real storm cloud of the simplified calculation model of a storm cloud, containing the spherical volume of V 0 by the radius of R 0 is shown that at R 0 ≈985 m and accordingly V 0 ≈4∙10 9 m 3 in the examined model of a storm cloud his indicated power descriptions arrive at the followings numeral values: charge of q Σ ≈−55.6 C, potential on the outward surface of cloud of φ R ≈−506 MV, electric energy of W 0 ≈14.1 GJ in a cloud and amplitude of aperiodic impulse of current of I mL ≈− 262.1 кА at duration of his flowing τ p ≈142.4 μs in the plasma channel of a long air spark digit of cloud on earth. This calculation information well correlates with the known experimental information, characteristic for the short shots of lightning in surface objects. The receive results will be instrumental in possibility of prognostication of a sticky storm wicket specialists at presence of only minimum initial information about a storm cloud in earthly troposphere. Originality. First at the analysis of a storm situation in troposphere of Earth offered approach, related to bringing the real storm cloud over the volume of V 0 to an equivalent on volume spherical storm cloud by the radius of R 0 , for which will apply the physical and mathematical vehicle of analysis of flowings in him electrophysics processes developed an author. Practical value. Application of the in practice calculation findings will allow to deepen scientific and technical knowledge in area of nature of atmospheric electricity, will be instrumental in further development of physics of linear lightning and successful decision of global problem of protecting from lightning of surface objects and auxiliary them personnel.
The evolution of computational physics over the last 30 years has been frighteningly fast, and the change has affected every aspect of the trade, including education, hardware, operating systems, languages, methodologies, standards, available libraries, information sharing, teaming, management, and specialization. This talk will concentrate on those changes to computational plasma and beam physics and engineering that result from the increasing specialization of the field, for which computationalists now typically concentrate on the computer science aspects, on the applied math issues. on the science implementation, or on science discovery.