Plasma Kinetic Energy Research Articles

A prospective randomised study between transurethral vaporisation using plasmakinetic energy and transurethral resection of the prostate

A prospective randomised study between transurethral vaporisation using plasmakinetic energy and transurethral resection of the prostate

A Laser Plasma Injector

A pulsed laser microinjector of low-temperature erosion plasma with a two-stage mechanism of generating and heating the working substance is described. Sequential stages of generation (laser ablation) and radiant–gas-dynamic heating of the working substance in the target and acceleration chambers of the injector are accomplished using two laser pulses with matched spectral, energy, and dynamic parameters, thus ensuring the obtainment of high values of the coefficients of the conversion of laser energy into the kinetic plasma energy (0.8) and the monochromaticity of the flow with a finely dosed mass flow rate.

Studies on the mechanism of energy transformation in implosion processes of the Z-pinches

In this paper, the energy transformation processes in neon gas-puff pinch and Al wire-array pinch were studied numerically by means of one-dimensional three-temperature radiation magneto-hydrodynamic code. In the Z-pinch, the main energy transformation process is the Coulomb collision process between ions and electrons. The second one is the photoelectric process and bremsstrahlung radiation process. The energy transformation in the Compton scattering process can be neglected in the computation. The x-ray energy radiated from Z-pinch was produced mainly by the photoelectric excitation and recombination process, and also by the bremsstrahlung radiation process and Compton scattering process. Numerical analysis indicates that the x-ray radiation energy can be larger or smaller than the maximal plasma kinetic energy. In our numerical simulation, the radiation energy from neon gas-puff pinch is smaller than the maximal plasma kinetic energy, however, that from Al wire-array pinch is larger than the maximal plasma kinetic energy. They are all smaller than the work done by magnetic pressure. The electric energy consumed by Ohm heating is rather small.

Tuning growth from clusters to continuous ultrathin films: Experiments and molecular dynamics simulations of Pd plasma sputter deposition

Plasma sputter deposition experiments and simple molecular dynamics calculations are performed for highlighting the effects of plasma ions and kinetic energy of palladium atoms on the morphology of thin films. A transition between cluster and continuous film growth is observed. It is attributed to the kinetic energy of the depositing sputtered palladium atoms and to high binding energy trapping sites resulting from the effects of ions incident on the surface during deposition. These high binding energy trapping sites act as additional nucleation centres that are allowed to be visited by the diffusing Pd atoms.

Magnetic Reconnection in Plasmas

Magnetic reconnection is one of the most fascinating subjects in plasma physics. It is basically a process by which the close tie between plasma motions and magnetic fields is broken. This enables plasma to penetrate magnetic boundaries; for instance, to enter into the Earth's magnetosphere from the solar wind. It is also a key process in explosive processes, converting magnetic energy into plasma kinetic and thermal energy, such as solar flares, magnetospheric substorms, as well as current disruptions in laboratory devices.The concept of magnetic reconnection was first introduced in 1946 by Ronald G. Giovannelli as a suggested mechanism for particle acceleration in solar flares. Consistent with modern definitions of reconnection, he related this process to the presence of an electric field in a region of low‐magnetic field strength or parallel to the magnetic field, both of which require the breakdown of the ideal magnetohydrodynamic (MHD) “frozen‐in” field concept and enable charged particle acceleration.

Laminar plasma dynamos

A new kind of dynamo utilizing flowing laboratory plasmas has been identified. The conversion of plasma kinetic energy to magnetic energy is verified numerically by kinematic dynamo simulations for magnetic Reynolds numbers above 210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed plasma dynamo corresponds to laminar flow topology. Modest plasma parameters (1–20 eV temperatures, 1019–1020 m−3 densities in 0.3–1.0 m scale-lengths driven by velocities on the order of the Alfvén critical ionization velocity) self-consistently satisfy the conditions needed for the magnetic field amplication. Growth rates for plasma dynamos are obtained numerically with different geometry and magnetic Reynolds numbers. Magnetic-field-free coaxial plasma guns can be used to sustain the plasma flow and the dynamo.

Two-dimensional MHD model of the reconnection diffusion region

Abstract. Magnetic reconnection is an important process providing a fast conversion of magnetic energy into thermal and kinetic plasma energy. In this concern, a key problem is that of the resistive diffusion region where the reconnection process is initiated. In this paper, the diffusion region is associated with a nonuniform conductivity localized to a small region. The nonsteady resistive incompressible MHD equations are solved numerically for the case of symmetric reconnection of antiparallel magnetic fields. A Petschek type steady-state solution is obtained as a result of time relaxation of the reconnection layer structure from an arbitrary initial stage. The structure of the diffusion region is studied for various ratios of maximum and minimum values of the plasma resistivity. The effective length of the diffusion region and the reconnection rate are determined as functions of the length scale and the maximum of the resistivity. For sufficiently small length scale of the resistivity, the reconnection rate is shown to be consistent with Petschek's formula. By increasing the resistivity length scale and decreasing the resistivity maximum, the reconnection layer tends to be wider, and correspondingly, the reconnection rate tends to be more consistent with that of the Parker-Sweet regime.

Optical emission spectroscopy of nitrogen species and plasma plume induced by laser ablation combined with pulse modulated radio-frequency discharge

Combined laser ablation and pulse modulated radio-frequency (RF) discharge for deposition of CN x films was studied by the use of optical emission spectroscopy. Chemically active nitrogen was produced by RF discharge, concentrated between two small electrodes. Influence of RF power, nitrogen pressure, modulation frequency and pulse rate on nitrogen species production was researched. For the same system plasma expansion rate, kinetic energy and concentration of carbon ions emitted by laser from graphite target were determined by Langmuir probes measurement.

Dissipation of Kinetic Energy in a Magnetic Dynamo

In a dynamo the magnetic field grows exponentially for some time. If there is no energy injected into the system, this growth must be done at the expense of the plasma kinetic energy. It is proved that for a certain growth rate, the kinetic energy decreases at least by a fixed amount independent of how large the magnetic field is; hence velocity fields allowing dynamos posses a minimum rate of dissipation. The key of the proof is a new inequality on the induction equation.

On the pressure balance in the distant magnetotail

Pressure balance between the lobe and the plasma sheet in the distant magnetotail is statistically studied with data obtained by the Geotail spacecraft. We selected events where the spacecraft traversed from the lobe to the neutral sheet and vice versa. As a result, we have found that the total pressure variations can be categorized by three types. Type 1, in which the total pressure is kept almost constant during the crossings, contains about a half of all events. This type is regarded as an average static feature of the distant magnetotail. Type 2 and Type 3 events are characterized by enhancement and depression of the total pressure in the plasma sheet, respectively. While the excess total pressure in Type 2 events can be explained by the passage of a plasmoid during the crossing, characteristics of Type 3 events suggest that they are located near the reconnection region. Depression of the total pressure indicates that part of the total pressure (energy density) is converted into plasma kinetic energy across a slow‐mode shock boundary.

MHD model of astrophysical jets

Astrophysical jets are modelled by the exact axially symmetric equilibria of plasma in the gravitational field of an attracting center. The derived solutions have an arbitrary constant partition between the plasma magnetic and kinetic energy and generalize the Chandrasekhar equipartition solution. The obtained equilibria are ergodic in variable z and depend on an arbitrary integer N and arbitrary parameters β, a 1,…, a N−1 , b 1,…, b N−1 . Near the attracting center, the solutions have either an accretion hyperboloid or disk or cone. The latter does not depend on the above parameters and has the semi-vertical angle of 60°.

Transition of plasma into a strongly-coupled state as a possible reason for anomalous resistance in active space experiments

A well-known phenomenon in the experiments on plasma injection in space is an appearance of anomalous electric resistance, which is usually attributed to the plasma turbulence. As is shown in our study, there may be yet another reason for this effect, namely, transition of the plasma into a strongly-coupled state in the process of its adiabatic expansion in vacuum. Since the kinetic energy of plasma decreases more rapidly than Coulomb energy, most electrons turn out to be quasi-localized in the vicinity of nearby ions. As a result, the electric current can be transferred only by a relatively small part of electrons, corresponding to the high-energy tail of the distribution function. The concentration of free charge carriers, calculated in our study, turns out to be independent of the plasma temperature and determined only by its density. (This features are somewhat similar, from the formal point of view, to the properties of degenerate Fermi gas.)

Trans-Fast MHD Winds in a Pulsar Magnetosphere

We consider the problem of how a pulsar wind dominated by electro-magnetic energy converts itself into a kinetic energy-dominated wind, that is required by magnetohydrodynamical (MHD) models of interaction between the pulsar and the nebula. It is known that stationary, ideal-MHD wind models based on radial configurations are incapable of explaining the energy conversion from the electro-magnetic energy to the plasma's kinetic energy. For non-radial field geometries, we consider a detailed analysis of the critical conditions of trans-fast MHD winds and discuss the effects of the magnetic field on the wind acceleration. Although the flow properties associate with the magnetic flux tube divergence, we survey the acceptable ranges of the wind parameters as a pulsar wind. Further, we demonstrate the Crab pulsar wind with a magnetic flux tube diverging as ∝ x−0.4 . We see that the rapid acceleration is caused by a nearby Alfvén point; the velocity is almost terminated within several thouthand times of the fast magnetosonic point; thus, the kinetic energy-dominated wind is realized.

Observations of visible light emission from interactions between an electrothermal plasma and a propellant

A set of experiments has been conducted on the experimental plasma-propellant interaction facility PIPE to measure the burn rates of JA2 solid propellant as a function of plasma impingement angle with respect to the propellant surface. The propellant test stand is designed such that the angle of plasma impact on the propellant surface can be varied 0 to 90 degrees. Optical emission spectroscopy measurements were taken during these shots. Fiber optics were situated in two places, one closer to the plasma source and the second at the propellant's rear edge near the point of impact of plasma and propellant. The fiber optics are connected to an optical multichannel analyzer set to observe neutral copper lines and molecular C/sub 2/ Swan Bands in the 505-585 nm spectral region. Time-averaged core are temperatures of 8,800 to 14,000 K and plasma densities of 2/spl times/10/sup 25/ to 4.5/spl times/10/sup 23/ m/sup -3/ have been deduced by measurements along the axis of the device using the relative intensities and the Stark broadening of the copper lines. As the angle of plasma impact with the propellant surface increases from D to 90/spl deg/, the overall radiant emission increases, falls and increases. However, the measured plasma temperature decreases gradually and plasma density falls by nearly a factor of two before increasing substantially at 90/spl deg/. Comparisons with the measured burn rates of the JA2 propellant versus inclination angles suggests a stronger correlation of plasma burn rate with plasma kinetic energy than with the radiative heat flux.

Distant tail behavior during high speed solar wind streams and magnetic storms

We have examined the ISEE 3 distant tail data during three intense (Dst < −100 nT) magnetic storms and have identified the tail response to high‐speed solar wind streams, interplanetary magnetic clouds, and near‐Earth storms. The three storms have a peak Dst ranging from −150 to −220 nT and occur on January 9, February 4, and August 8, 1983. During the storm onsets, the fast solar wind and magnetic field dynamic pressure (B2/8π+ΣnikTi) fluctuations moved the tail across the spacecraft multiple times. The magnetotail is strongly compressed by the outside sheath pressure. The lobe field strength can usually be predicted by the pressure balance. The strongest lobe field magnitude detected is 37 nT during storm main phase on January 10, which is higher than the sheath field by 5 – 10 nT. The sheath plasma pressure accounts for the higher lobe field strengths. However, for the February 4 storm, we find that three tail lobe encounters are not in static balance with sheath pressure. During the storm times, the field magnitudes of the lobe and plasma sheet increase by a factor of 3–5 relative to the quiet time. The temperature and density in both regions also increase by factors of 2–3, but with little plasma β changes, as one would expect. Under the assumption of tail flux conservation, increased sheath pressure implies a reduced tail size. Besides the tail size changes, the location of the nominal tail axis is controlled by solar wind flow orientation. This study shows that more than 70% of tail in‐and‐out events are predicted by either of these external mechanisms (changes of tail size due to the external pressure and the solar wind directional changes). Nine tail plasma sheet jettings and 12 slow‐mode shocks have been detected during the three storms. One remarkable feature of the jettings is very strong earthward flow (up to 1200 km/s) and tailward flow (up to 1500 km/s). The solar wind speed for these events was only ∼900 km/s. Both tail flow events have the highest speeds found to date. The preponderance of such a strong earthward flow indicates that during magnetic storms, magnetic reconnection occurs at locations well beyond the distance of ISEE 3. Through the interface of slow‐mode shocks between the tail lobe and the plasma sheet/boundary layer, magnetic energy is being converted into plasma thermal and kinetic energy by the magnetic merging process. The predicted downstream plasma jetting speed (978 km/s) is consistent with the observations (1000 km/s) in the boundary layer. One surprising feature is that this reconnection process seems to be quite prominent during the storm recovery phase. One possible suggestion is that the dynamics of the distant tail are not at all related to magnetic storms and substorms but is an aftereffect, releasing extra magnetic tail energy by field sloughing via these reconnection events, accompanying the plasma sheet expansion.

Plasma confinement and other effects of magnetic moment from standing waves in Vlasov plasma

A non-oscillating (zero-harmonic) spatially varying magnetic moment, from the wave-induced bending of the direction of motion of charged constitutents of a Vlasov plasma, along the path of a standing-wave pattern, has been worked out. This field is maximum at the even multiples of λ/4 (λ is the wavelength). So maximum plasma kinetic energy is transformed into the magnetic energy, in the zones of the antinodes, confining the plasma particles there. The reduction of kinetic temperature of the plasma in the direction of wave propagation, from pressure anisotropy of this magnetic-moment field, has been calculated for both dispersive and standing waves. The palsma beads (congested assemblies of charges), thereby formed at the antinodes (which are points of maximum concentration of magnetic energy), create a plasma confinement situation. Experiments can detect the resulting change in opacity of the plasma in the wave path, and its dependence on the kinetic temperature optically, or by magnetic tape. This magnetic bottle effect, a consequence of the spatial variation of the induced magnetic moment along the direction of wave propagation, is a primary device of plasma confinement.

Optimization of K-shell emission in aluminum z-pinch implosions: Theory versus experiment.

Two sets of [ital z]-pinch experiments were recently completed at the Saturn and Phoenix facilities of Sandia National Laboratories and the Naval Surface Warfare Center, respectively, using aluminum wire arrays of different wire and array diameters. Measurements of the total x-ray yield from the [ital K] shell of aluminum were made. In this paper, a comparison of these measurements is made to both theoretical predictions and to a similar set of earlier measurements that were made at the Double Eagle facility of Physics International Company. These three sets of yield measurements have points of agreement with predicted yields and with each other, but they also show points of mutual disagreement, whose significance is discussed. The data are analyzed using a slightly revised version of a previously published [ital K]-shell yield scaling law, and they support the existence of a reasonably well defined region in (load mass)--(implosion velocity) space in which plasma kinetic energy is efficiently converted into [ital K]-shell x rays. Furthermore, a correlation is observed between the inferred conversion efficiencies and the times in which the implosions occur relative to the times when each generator's short-circuit current reaches its peak value. Finally, unlike the Double Eagle experiments, the largestmore » measured yields in the new experiments were observed to occur at the upper velocity boundary of the efficient emission region. Moreover, the observed yields are in fairly good quantitative agreement with an earlier scaling law prediction of the maximum [ital K]-shell x-ray yield from aluminum as a function of load mass assuming kinetic energy conversion alone.« less

Transport of energy and momentum due to spatial Landau damping and growth of electrostatic waves

It is shown that Landau damping in space (LDS), occurring for time-periodic electrostatic waves, does not lead to any deposition of energy in plasmas. A steady-state balance and a steady-state transport of energy, momentum and particles take place both for damped and growing waves. Because of the phase interference of coherent free and forced particle oscillations, the oscillatory energy of particles increases in the direction of wave propagation; the time-averaged flow of plasma kinetic energy being constant in space for these waves, the LDS must take place for a Maxwellian plasma in order to compensate for the growth of the particle oscillatory energy in space.

Momentum transport near a magnetic X line in collisionless reconnection

Plasma dynamics and momentum transport near an X line during time‐dependent magnetic reconnection in a collisionless plasma are investigated based on two‐dimensional particle simulations. We find that a weakly skewed velocity distribution is formed near the magnetic X line, leading to the presence of off‐diagonal elements of the plasma pressure tensor. Let the reconnection electric field be in the y direction. The gradients of the off‐diagonal elements of the pressure tensor can provide a transport of the y momentum. During the normal magnetic reconnection, the momentum transport associated with the off‐diagonal terms of the pressure tensor mediates a transfer of the y momentum from the region near the X line to regions outside the X line. A period of “reverse magnetic reconnection,” during which the plasma kinetic energy is converted into magnetic energy, is also observed in the simulation. When reverse reconnection occurs, the gradients of the off‐diagonal pressure tensor elements can mediate a transfer of y momentum into the X line. It is found that the inertial term also plays a significant role in the force balance near the magnetic X line. An explanation for the origin of the off‐diagonal pressure terms is also given in this paper.

Free energy in plasmas under wave-induced diffusion

When waves propagate through a bounded plasma, the wave may be amplified or damped at the expense of the plasma kinetic energy. In many cases of interest, the primary effect of the wave is to cause plasma diffusion in velocity and configuration space. In the absence of collisions, the rearrangement of the plasma conserves entropy, as large-grain structures are mixed and fine-grain structures emerge. The maximum extractable energy by waves so diffusing the plasma is a quantity of fundamental interest; it can be defined, but it is difficult to calculate. Through the consideration of specific examples, certain strategies for maximizing energy extraction are identified.