Direct Conversion of the Energy of Laser and Fusion Plasma Clouds to Electrical Energy During Expansion in a Magnetic Field

The paper deals with the physical and electrotechnical principles of the promising method of direct conversion of the kinetic energy of an expanding plasma cloud to electrical energy by inductive generation of currents in short–circuited load coils that enclose the plasma and are oriented across the external magnetic field. An analysis of plasma deceleration by a magnetic field and transfer of plasma energy to an inductive load gave a solution of the problem in general form and the dimensionless parameters of the problem that determine the deceleration radius, the coil current, and the theoretical conversion efficiency. The role of the basic physical effects, including parasitic ones (plasma instabilities and Joule heating), influencing the real efficiency is assessed. A comparison of the results with data of experiments with laser–produced plasma clouds on a KI–1 facility and with available numerical results shows that in the optimized version of the method for conversion of inertial confinement fusion energy, a 30% efficiency can be achieved.     

Cascade Magnetic Cumulation Generator on the Basis of Inductively Coupled Circuits with A Variable Coupling Coefficient

A scheme of a multicascade magnetic cumulation generator based on a dynamic variation of the coupling coefficient of inductively coupled circuits is proposed. Each cascade contains two circuits including two pairs of inductively coupled coils. One pair of coils is subjected to simultaneous deformation, and one of the coils in the other pair is arranged with the opposite connection. It is shown that the energy in the load can be gradually increased (from one cascade to another) by using additional cascades. By an example of a two-cascade system, the proposed circuit is compared to the known circuits of the cascade system design based on the magnetic cumulation principle (generator with a step-up transformer and dynamic transformer). Within the framework of the model that ignores the ohmic resistance of conductors, it is demonstrated that the proposed scheme allows one to obtain a greater energy in the high-inductance load than the schemes with a step-up or dynamic transformer owing to a change in the sign of the magnetic flux in the secondary circuit. It is found that the increase in energy in the new scheme is independent of the coupling coefficient (at high values of this coefficient) and becomes greater as the number of cascades is increased.     

Simulation of the motion and heating of an irregular plasma

A physicomathematical model for plasma heating and confinement is formulated on the basis of some assumptions on the behavior of a dense plasma cloud in a magnetic field. The model allows for the ionization and heating of the plasma cloud by the surrounding deuterium plasma due to heat conduction and heating by a superthermal electron current. The expansion of a plasma cloud in an external magnetic field is studied using some simplifications in a magnetohydrodynamic approximation. Plasma heating is modeled by an external source. The basic equations include continuity, motion, energy, and magneticfield equations. For numerical solution of the problem, we developed a finitedifference scheme of the type of a universal algorithm with splitting into physical processes and spatial directions, which allowed us to obtain separate solutions of the equations of magnetic induction and gas dynamics. Calculations of the propagation of a plasma cloud heated by a source in an external magnetic field were performed. The mechanism of the effect of the magnetic field and heat source on plasma cloud expansion is determined. The results agree qualitatively with experimental data.     

Magnetosonic analysis and the method for diagnostics of expansion of a plasma cloud in a magnetized background

The problem of sub-Alfvén expansion of a superconducting plasma sphere in a homogeneous magnetized background is considered. The specifics of a self-consistent model of a low-frequency linear MHD approximation that we used in the present paper is the simultaneous allowance for the energy necessary for maintaining the field and plasma equilibrium at a moving boundary and the additional perturbation of a decelerating field generated by the currents induced in a background plasma. This has allowed us to clarify significantly the dependence of the radiated magnetohydrodynamic energy on the Mach-Alfvén number. We found and calibrated universal dynamic characteristics on the basis of which we developed new techniques for determining the initial energy and the velocities of expansion of an explosive plasma cloud with the use of the peak values of magnetic signals in the near (quasistatic), transient, and wave zones. The possibility of effective application of these techniques in experiments on laser-plasma cloud generation in a vacuum homogeneous magnetic field is shown. Institute of Laser Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 3–13, May–June, 1998.     

Expansion of a variable-conductivity plasmoid with small hydromagnetic-interaction parameter in an external magnetic field

The author considers the induction interaction of an expanding variable-conductivity plasmoid which is temperature dependent. The external uniform magnetic field is specified as an arbitrary function of time.The following two problems are solved assuming a small hydromagnetic-interaction parameter (product of the magnetic Reynolds number and the ratio of the characteristic values of the magnetic pressure to the static plasma pressure): expansion at constant velocity and expansion into free space.The work A done by the plasma against the electrical body forces and the Joule losses Q in the plasma per unit time are calculated. A relative analysis of the degree of isoentropicity of the expansion process or the internal efficiency = (A–Q)/A as a function of the magnetic Reynolds number, adiabatic curve, and plasmoid shape (plane-symmetric and axisymmetric) is given.The results of this calculation can be used as a rough estimate of the efficiency of the MHD method for converting thermal energy into electrical energy.The author wishes to thank L. A. Zaklyaz'minskii for his valuable comments and his interest in the study.     

Optimal electromagnetic energy extraction from transverse galloping

A fully coupled electro-fluid-elastic model for electromagnetic energy harvesting from Transverse Galloping is presented here. The model considers a one degree-of-freedom galloping oscillator where fluid forces are described resorting to quasi-steady conditions; the electromagnetic generator is modelled by an equivalent electrical circuit where power is dissipated at an electrical load resistance; the galloping oscillator and the electromagnetic model are coupled appropriately. Two different levels of simplification have been made depending on the comparison between the characteristic electrical and mechanical timescales. The effect of the electrical resistance load on the energy harvested is studied theoretically. For fixed geometry and mechanical parameters, it has been found that there exists an optimal electrical resistance load for each reduced velocity. On the practical side, this result can be helpful to design tracking-point strategies to maximize energy harvesting for variable flow velocity conditions.     

Numerical simulation of plasma motion in a magnetic field. Two-dimensional case

A model of dynamics and heating of a plasma cloud in a magnetic field is considered in a two-temperature approximation. Based on a predictor-corrector-type implicit difference scheme, spreading of a plasma cloud in an external magnetic field is numerically simulated, and the influence of this field on spread dynamics is evaluated. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 121–132, May–June, 2007.     

Generation of electromagnetic energy in a magnetic cumulation generator with the use of inductively coupled circuits with a variable coupling coefficient

A method of generation of electromagnetic energy and magnetic flux in a magnetic cumulation generator is proposed. The method is based on dynamic variation of the circuit coupling coefficient. This circuit is compared with other available circuits of magnetic energy generation with the help of magnetic cumulation (classical magnetic cumulation generator, generator with transformer coupling, and generator with a dynamic transformer). It is demonstrated that the proposed method allows obtaining high values of magnetic energy. The proposed circuit is found to be more effective than the known transformer circuit. Experiments on electromagnetic energy generation are performed, which demonstrate the efficiency of the proposed method.     

Structural and electrical dynamics of a grating-patterned triboelectric energy harvester with stick–slip oscillation and magnetic bistability

The majority of research work on triboelectric energy harvesting is on material science, manufacturing and electric circuit design. There is a lack of in-depth research into structural dynamics which is crucial for power generation in triboelectric energy harvesting. In this paper, a novel triboelectric energy harvester with a compact structure working in sliding mode is developed, which is in the form of a casing and an oscillator inside. Unlike most sliding-mode harvesters using single-unit films, the proposed harvester utilizes grating-patterned films which are much more efficient. A bistable mechanism consisting of two pairs of magnets is employed for broadening the frequency bandwidth. A theoretical model is established for the harvester, which couples the structural dynamics domain and electrical dynamics domain. This paper presents the first study about the nonlinear structural dynamics of a triboelectric energy harvester with grating-patterned films, which is also the first triboelectric energy harvester integrating grating-patterned films with a bistable magnetic system for power performance enhancement. Theoretical studies are carried out from the perspectives of both structural and electrical dynamics. Surface charge density and segment configuration of the films affect whether the electrostatic force influences the structural dynamics, which can be neglected under a low surface charge density. Differences in structural response and electrical output are found between a velocity-dependent model and Coulomb’s model for modelling the friction in the triboelectric energy harvesting system. The bistable mechanism can effectively improve the output voltage under low-frequency excitations. Additionally, the output voltage can also be obviously enhanced through increasing the number of the hollowed-out units of the grating-patterned films, which also results in a slight decrease in the optimal load resistance of the harvester. These findings enable innovative designs for triboelectric energy harvesters and provide fabrication guidelines in practical applications.

     

Calculating scheme and switching-on of the load of plane explosive-driven magnetic generators

A scheme is described for calculating explosive-driven magnetic generators, and analytical and numerical calculations are made of the problem of switching a generator on to a constant ohmic and induction load, to a load whose resistance rises linearly with the temperature, and to a plasma load with equilibrium radiation. In the latter case, a calculation is made of a variant involving switching on the load through a matched transformer.Translated from Zhurnal Prikladnoi Mekhanika i Tekhnicheskoi Fiziki, No. 2, pp. 37–41, March–April, 1973.     

Motion of a conductive piston in a channel with variable inductance

The motion of a conductive piston in the channel of a magnetohydrodynamic (MHD) generator of the conduction type with compound electrodes is considered. Formulas are obtained for calculation of the energy characteristics of the pulse MHD generator for various operational regimes. It is shown that in an MHD generator at magnetic Reynolds number values Re_m = ₀u₀ 1 (where ₀ is the permeability of a vacuum, is the electrical conductivity of the piston, u₀ is the initial velocity, and is the characteristic dimension), the energy transferred to an ohmic load may significantly exceed the values obtained in [1, 2]. Conditions for high-efficiency transformation of piston kinetic energy to electrical energy are considered for limiting values of the ratio of the latter to initial magnetic field energy in the generator channel.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 6, pp. 41–46, November–December, 1973.The authors thank V. I. Yakovlev for his helpful evaluation.     

Method of designing explosive-driven magnetic field generators

A method of designing explosive-driven magnetic field generators that allows us to establish a dependence between the parameters of the generator circuit, in which the greatest energy release occurs under a time-invariant resistive load, is described. The problem of switching two-dimensional generators to a load whose resistance linearly increases with temperature is analytically solved as an example. The theoretical possibility of designing a generator in which the power released under the resistive load R(t) varies in a specified way with time is demonstrated. Types of current pulse, power, and energy released in the load are studied in the case of different generator circuit parameters.Translated from Zhurnal Prikladnoi Mekhaniki Tekhnicheskoi Fiziki, No. 1, pp. 120–127, January–February, 1976.The author to wxpress his appreciation to E. I. Bichenkov for useful remarks.     

Computational and experimental study of a railplug igniter

The plasma plume generated by a new type of high energy igniter known as the railplug is examined. The railplug is a miniaturized railgun that has the potential for improving ignition characteristics of combustible mixtures in engines. The objective of the study is to gain an understanding of the characteristics of the plasma created by a transparent railplug and to validate a multidimensional computer simulation of the plasma and shock fronts. The nature of the plume emitted by the railplug was examined for three levels of electrical energy while firing into air at a pressure of 1 atm. The computer model is to be used to predict trends in railplug performance for various railplug designs, energies, and ambient conditions. The velocity of the plasma movement inside a transparent railplug was measured, as well as the velocity of the plume ejected from the cavity. A shock is produced at the initiation point of the arc and propagates down the cavity, eventually exiting the plug. The velocity of the shock was both measured experimentally and simulated by the model. The computer simulation produces a mushroom-shaped plasma plume at the railplug exit similar to that observed in the shadowgraph photos. The simulation also reproduced the toroidal circulation observed at the plug exit in the shadowgraphs, the radial expansion, and the penetration depth of the plume. The trend of linearly increasing plasma kinetic energy with stored electrical energy predicted by the simulation was verified by shadowgraph photos. The agreement between the experiments and the simulations suggests that the multidimensional model holds promise as a predictive design tool.     

Equilibrium and stability in a high-current discharge in a dense plasma under conditions of radiative conduction

Equilibrium and stability are examined for a high-current self-compressed discharge:in a dense, optically opaque plasma of finite conductivity, with allowance for dissipation via radiative heat transfer. If the thermal conductivity is high, the plasma temperature is virtually constant throughout the cross-section of the discharge, whereas the density and pressure fall off fairly rapidly away from the axis. The spectrum for small oscillations shows that such an equilibrium discharge is unstable with respect to short-wave hydrodynamic oscillations (bending and necking) if the plasma conductivity is low. Instability can develop only for long-wave perturbations in a cylindrical discharge, and also for a nonequilibrium discharge when the rise time is iess than the equilibration time. A planar equilibrium discharge is stable, while a cylindrical equilibrium discharge in a dense low-temperature plasma is more stable than one in a high-temperature plasma.There have been several discussions of the use of high-current discharges in dense plasmas as light sources for laser pumping. The choice of discharge dimensions is governed by the temperature T of the radiating surface, which should be 3–10 eV. Only ohmic heating can allow one to keep a plasma at such a temperature for a sufficiently long time (around 100 vsec). On the other hand, hydrodynamic instabilities (bends, necks, hot spots) can arise in a dense plasma carrying a current, which can lead to current interruption and plasma dispersal (see [1] for literature). Stability is therfore a major problem in the use of such discharges as light sources. However, it is not correct to apply the theory of [1] to such discharges, since this theory is for a not very dense, hot. transparent plasma under conditions such that radiation does not play a major part in the development of the discharge, whereas a discharge in a dense, optically opaque plasma is best as a light source. Such a plasma can have considerable radiative energy transfer, which can influence the entire character of the discharge. Moreover, effects due to the finite conductivity (diffusion of electric and magnetic fields) may play major parts at these relatively low temperatures. Here we present a theoretical discussion of the equilibrium and stability of a high-current discharge in a dense, optically opaque plasma having a finite conductivity and considerable radiative heat transfer.We are indebted to G. V. Mikhailov and V. B. Rozanov for many discussions.     

Charging of an inductive accumulator from an explosive-type magnetic generator through an electrical explosive-type current breaker

Analytical investigations were made of electromagnetic processes with the work of an explosive-type magnetic generator, in a series-connected inductive-type accumulator and a current breaker based on an exploding wire. A solution is obtained in dimensionless form for a model of a current breaker based on an ohmic resistance, whose value rises linearly with the temperature. The conditions are determined under which an inductive load can be connected in parallel to the current breaker; under these circumstances, the current of the load branch remains small during the whole charging stage.     

Dispersion of a plasma cloud in a uniform magnetic field

The numerical solution of the two-dimensional gasdynamical problem of the dispersion of a plasma cloud in a magnetic field which is uniform to infinity is described. The disturbance of the field and the deformation of the cloud are taken into account self-consistently.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 146–148, July–August, 1974.In conclusion the authors thank A. I. Barchenkov, G. V0 2harova, S. A. Kuchai, V. G. Rogachev, and V. P. Statsenko for valuable advice and assistance in the work.     

Functional enhancement of a non-equilibrium plasma jet by seeding in the applied magnetic field

The experimental study is conducted to clarify the functional enhancement of a non-equilibrium argon plasma jet by seeding potassium in the applied magnetic field to extend its industrial applications. It is shown that the plasma parameters such as electron number density and electron temperature increase considerably by seeding especially in the applied magnetic field, which results in the easy enhancement of transport properties such as electrical conductivity and electron thermal conductivity. Finally, the infrared thermography is shown to visualize the relative variation of radiative temperature field comparing both with seeding and without seeding.     

The acceleration of electrons in a boundary layer

The effect of the redistribution of energy between ion and electron components for the motion of a plasma in a nonuniform magnetic field is considered on the example of a flat model of an equilibrium boundary layer between a rarefied plasma and a magnetic field in the relativistic invariant form. The relativistic and polarization corrections to the classical theory are found. Results are given for a numerical solution of the problem.     

Probe measurements in the channel of a magnetic annular arc

The profiles of the electron temperature and density in the channel of a magnetic annular arc have been measured with the help of an electrical circuit developed for large probe currents.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 5, pp. 158–160, September–October, 1973.     

低碳钢塑性变形量磁评定法研究

针对塑性变形量评定的局限问题,基于铁磁材料塑性变形致位错在不同方向分布不同的现象,研究了磁测法在定量评定低碳钢塑性变形量方面的应用前景。实验以工程中常用的低碳钢Q195钢板为测试材料,制作了形状尺寸一致的一批试件,并对其进行了不同程度的塑性变形量加载。通过搭建的磁化检测系统,采用相同强度及频率的正弦波激励,对所有样品进行了不同方向的磁化;同时经线圈及隧道磁敏电阻(TMR)采集了每次磁化的磁化曲线,提取了磁化曲线特征参数,对比了其与塑性变形量的定量关系。结果表明:随着塑性变形量的增加,铁磁钢材在同一磁场强度下产生的磁感应强度也会变大;沿主塑性变形方向磁化时,磁滞消耗能量最少,沿主塑性变形垂直方向磁化时,磁滞消耗的能量最多;磁路内磁场在主塑性变形方向上对塑变量的变化最敏感,而磁路外磁场在主塑变垂直方向上对塑变量的变化最敏感。实现了铁磁材料磁特征参数与塑性变形量的定量关联。本研究为开发简捷的铁磁材料塑性变形量无损评定磁方法奠定了基础。