One-dimensional Plasma Research Articles

Properties of unidirectional absorption in one-dimensional plasma photonic crystals with ultra-wideband

In this paper, the properties of tunable unidirectional absorption in one-dimensional (1D) plasma photonic crystals (PPCs) are theoretically investigated by the transfer matrix method. The PPCs are composed of dielectric layers and non-magnetized and magnetized plasma layers. The simulated results show that a unidirectional ultra-wideband absorption region (absorption rate is larger than 0.9) whose relative bandwidth is 36.2% can be obtained in the proposed 1D PPCs. The effects of the parameters of such PPCs on the features of the unidirectional absorption region (UAR) are also studied. The computed results illustrate that the obtained UARs can be tuned by those parameters as mentioned above, and also show us an alternative way to realize the reconfigurable unidirectional applications in the 1D PPCs.

Wavelength dependence of laser plasma interaction related to shock ignition approach

AbstractThis paper provides a summary of recent research connected with the shock ignition (SI) concept of the inertial confinement fusion which was carried out at PALS. In the experiments, Cu planar targets coated with a thin CH layer were used. Two-beam irradiation experiment was applied to investigate the effect of preliminary produced plasma to shock-wave generation. The 1ω or 3ω main beam with a high intensity >1015W/cm2generates shock wave, while the other 1ω beam with the intensity below 1014W/cm2creates CH pre-plasma simulating the pre-compressed plasma related to SI. Influence of laser wavelength on absorbed energy transfer to shock wave was studied by means of femtosecond interferometry and measuring the crater volume. To characterize the hot electron and ion emission, two-dimensional (2D) Kα-imaging of Cu plasma and grid collector measurements were used. In single 1ω beam experiments energy transport by fast electrons produced by resonant absorption made a significant contribution to shock-wave pressure. However, two-beam experiments with 1ω main beam show that the pre-plasma is strongly degrading the scalelength which leads to decreasing the fast electron energy contribution to shock pressure. In both the single 3ω beam experiments and the two-beam experiments with the 3ω main beam, do not show any clear influence of fast electron transport on shock-wave pressure. The non-monotonic behavior of the scalelength at changing the laser beam focal radius in both presence and absence of pre-plasma reflects the competition of plasma motion and electron heat conduction under the conditions of one-dimensional and 2D plasma expansion at large and small focal radii, respectively.

Realization of tunable TE/TM wave splitter with one-dimensional plasma dielectric photonic crystal

A tunable transverse electric (TE) and transverse magnetic (TM) wave splitter using one-dimensional plasma dielectric photonic crystal which consists of plasma arranged periodically in a host dielectric medium is proposed. We performed a detailed study to explore the phenomena of reflection and transmission that occurs on obliquely incident electromagnetic wave propagating in the proposed plasma dielectric photonic crystal. We exactly calculated the transmittance based on the transfer matrix method. We find that if the parameters are selected appropriately, in the TE-stop or TM-stop frequency region, the other polarized component TM or TE wave is totally transmitted. The results also show that the dielectric constant, plasma thickness, incident angle and the applied magnetic field have significantly changed the properties of the TE/TM wave splitter. Moreover, the external magnetic field can be used as a kind of tunable method once the splitter is fabricated. Parameter dependence of the effects for the TE/TM wave splitter is calculated and discussed.

Extrinsic magnetized plasma Fabry–Perot resonator

This study uses the transfer matrix method to compute the transmission properties of electromagnetic waves within the microwave region of the one-dimensional extrinsic magnetized plasma periodic multilayer. The layer thicknesses of the extrinsic photonic structure were determined by the spatially varying external magnetic field. Apart from a few photonic bandgaps, a cluster of the resonant peak was noticed within the microwave region in the absence of a defect layer. The envelope of such resonant peaks was controlled by changing the layer’s thickness, the strength of the external magnetic field and the electron density of the magnetized cold plasma. With these features, periodic extrinsic magnetized plasma photonic crystal would offer a potential for designing a tunable multi-resonance periodic multilayer Fabry–Perot resonator for microwave applications.

Expansion of a collisionless hypersonic plasma plume into a vacuum.

Both fully kinetic and hybrid particle-in-cell (PIC) simulations are performed to investigate the two-dimensional (2D) expansion of a collisionless, hypersonic plasma plume into a vacuum. The fully kinetic PIC simulations are carried out using the real ion-to-electron mass ratios of H^{+}, Ar^{+}, and Xe^{+}, while the hybrid PIC model assumes the electrons to be a massless, isothermal fluid. We find that the hypersonic plasma plume exhibits four distinct regions, the unperturbed, quasisteady expansion, self-similar expansion and electron front regions. The behavior of electrons is strongly anisotropic, causing considerably different expansion characteristics between the plume direction and the transverse direction. Along the plume direction, the expansion dynamics is similar to that of the classical one-dimensional (1D) semi-infinite plasma expansion and the electrons are almost isothermal. In the transverse direction, the expansion process can be considered analogous to the 1D expansion of a finite plasma where the effect of electron cooling is important. This anisotropic characteristic is attributed to the amount of electron thermal energy available from the source in different directions. A direct comparison between the hybrid and full PIC simulations shows that the widely used equilibrium isothermal electron fluid model is in general not valid for modeling the expansion of a collisionless plasma plume.

General self-similar solution for expansion of non-Maxwellian plasmas

In this work, self-similar expansion of one-dimensional collisionless plasma into a vacuum has been calculated for non-Maxwellian particles. It is known that, during the expansion, the initial Maxwellian electron velocity distribution function (DF) is deformed. In this paper, this deformation is illustrated by the Vlasov simulation of plasma expansion. A part of deformation is associated with the appearance of high energy (super thermal) electrons. Therefore, a more complete and realistic plasma model has to include the effect of the super thermal electrons. It is found that the resulting DF of simulation has good consistency with the generalized Lorentzian (kappa) DF. Then the self-similar calculations were carried out for cold ions while the electrons having Lorentzian DF. Finally, it was found that, by increasing the population of energetic electrons, the expansion takes place faster and the ions are accelerated to higher energies.

Design of the multichannel filter based on one-dimensional defect plasma photonic crystal

The transmission properties have been investigated for the anisotropic plasma photonic crystal (APPC) with defect layer. Based on the transfer matrix method (TMM), the total transmission coefficient for the symmetry APPC with defect layer has been deduced. The numerical simulations shows that transmittance spectrums are the same as those of the general plasma crystal when the thickness of the defect layer is small. With the increasing of the thickness of the defect layer, the transmittance peak is split into more transmittance peaks called as the defect modes, which is different from the general plasma crystal. The defect modes caused by the defect layer in the APPC open up another choices of multichannel filters for EM waves in practice.

On the inverse problem for Channell collisionless plasma equilibria

Vlasov–Maxwell equilibria are described by the self-consistent solutions of the time-independent Maxwell equations for the real-space dynamics of electromagnetic fields and the Vlasov equation for the phase-space dynamics of particle distribution functions (DFs) in a collisionless plasma. These two systems (macroscopic and microscopic) are coupled via the source terms in Maxwell’s equations, which are sums of velocity-space ‘moment’ integrals of the particle DF. This paper considers a particular subset of solutions of the broad plasma physics problem: ‘the inverse problem for collisionless equilibria’ (IPCE), viz. ‘given information regarding the macroscopic configuration of a collisionless plasma equilibrium, what self-consistent equilibrium DFs exist?’ We introduce the constants of motion approach to IPCE using the assumptions of a ‘modified Maxwellian’ DF, and a strictly neutral and spatially one-dimensional plasma, and this is consistent with ‘Channell’s method’ (Channell, 1976, Exact Vlasov-Maxwell equilibria with sheared magnetic fields. Phys. Fluids, 19, 1541–1545). In such circumstances, IPCE formally reduces to the inversion of Weierstrass transformations (Bilodeau, 1962, The Weierstrass transform and Hermite polynomials. Duke Math. J., 29, 293–308). These are the same transformations that feature in the initial value problem for the heat/diffusion equation. We discuss the various mathematical conditions that a candidate solution of IPCE must satisfy. One method that can be used to invert the Weierstrass transform is expansions in Hermite polynomials. Building on the results of Allanson et al. (2016, From one-dimensional fields to Vlasov equilibria: Theory and application of Hermite polynomials. Journal of Plasma Physics, 82, 905820306, http://doi:10.1017/S0022377816000519), we establish under what circumstances a solution obtained by these means converges and allows velocity moments of all orders. Ever since the seminal work by Bernstein et al. (1957, Exact nonlinear plasma oscillations. Phys. Rev., 108, 546–550) on ‘stationary’ electrostatic plasma waves, the necessary quality of non-negativity has been noted as a feature that any candidate solution of IPCE will not a priori satisfy. We discuss this problem in the context of Channell equilibria, for magnetized plasmas.

Numerical simulation of the multi-pulse phenomena in atmospheric-pressure dielectric barrier glow discharges in He/N2mixture

To further understand the formation mechanism of multi-pulse phenomena in atmospheric He/N2dielectric barrier glow discharge, the influence of nitrogen content on the multi current pulse phenomena is studied by a one-dimensional plasma fluid model. As nitrogen content increases, the first discharge current in the multi-pulse glow discharge becomes larger, and the gas gap voltage drop and the charges transported during the first discharge pulse are also increased, leading to the decrease of subsequent discharge current. When the increasing applied voltage cannot overcome the gas gap voltage drop in the first discharge pulse, the multi-pulse discharge mode will transit into a single pulse discharge mode. The numerical simulation results also show that the changes of discharge characteristics are mainly attributed to the Penning ionization between molecules of nitrogen and metastable atoms of helium.

Simulations of relativistic quantum plasmas using real-time lattice scalar QED.

Real-time lattice quantum electrodynamics (QED) provides a unique tool for simulating plasmas in the strong-field regime, where collective plasma scales are not well separated from relativistic-quantum scales. As a toy model, we study scalar QED, which describes self-consistent interactions between charged bosons and electromagnetic fields. To solve this model on a computer, we first discretize the scalar-QED action on a lattice, in a way that respects geometric structures of exterior calculus and U(1)-gauge symmetry. The lattice scalar QED can then be solved, in the classical-statistics regime, by advancing an ensemble of statistically equivalent initial conditions in time, using classical field equations obtained by extremizing the discrete action. To demonstrate the capability of our numerical scheme, we apply it to two example problems. The first example is the propagation of linear waves, where we recover analytic wave dispersion relations using numerical spectrum. The second example is an intense laser interacting with a one-dimensional plasma slab, where we demonstrate natural transition from wakefield acceleration to pair production when the wave amplitude exceeds the Schwinger threshold. Our real-time lattice scheme is fully explicit and respects local conservation laws, making it reliable for long-time dynamics. The algorithm is readily parallelized using domain decomposition, and the ensemble may be computed using quantum parallelism in the future.

The electromagnetic waves propagation in unmagnetized plasma media using parallelized finite-difference time-domain method

The finite-difference time-domain (FDTD) method has been commonly utilized to simulate the electromagnetic (EM) waves propagation in the plasma media. However, the FDTD method may bring about extra run-time on concerning computationally large and complicated EM problems. Fortunately, the FDTD method is easy to parallelize. Besides, GPU has been widely used for parallel computing due to its unique SPMD (Single Program Multiple Data) architecture. In this paper, we represent the parallel Runge-Kutta exponential time differencing scheme FDTD (RKETD) method for the unmagnetized plasma implemented on GPU. The detailed flowchart of parallel RKETD-FDTD method is described. The accuracy and acceleration performance of the proposed parallel RKETD-FDTD method implemented on GPU are substantiated by calculating the reflection and transmission coefficients for one-dimensional unmagnetized plasma slab. The results indicate that the numerical precision of the parallel RKETD-FDTD scheme is consistent with that of the code implemented on CPU. The computation efficiency is greatly improved compared with merely CPU-based serial RKETD-FDTD method. Moreover, the comparisons of the performance of CUDA-based GPU parallel program, Open MP (Open Multi-Processing)-based CPU parallel program, and single-CPU serial program on the same host computer are done. Compared with the serial program, both parallel programs get good results, while GPU-based parallel program gains better result.

C70 increases the plasmonic signal of gold-atom chains on Si(553)

Infrared plasmonic excitations of the quasi-one dimensional gold-atom induced superstructures on silicon surfaces are particularly sensitive to doping effects. Such effects, here related to C70 adsorption, can be clearly measured as we show for gold atom chains on the Si(553) surface at room temperature. The strong plasmonic signal that is exclusively present for polarization along the chain direction does not disappear under C70 exposure. In contrast, it increases for adsorption of the first monolayer. The rising intensity corresponds to an increase of the one-dimensional plasma frequency. This process saturates at a coverage corresponding to ca. one C70 per 1 × 2 surface unit cell. The observed plasmonic behaviour upon C70 adsorption is opposite to the consequences of electron donating gold ad-atoms on the plasmonic response. The increase of the one-dimensional plasma frequency upon C70 adsorption is accompanied by an increase of the electronic scattering rate, which is in accord to the theory on adsorbate induced surface resistivity.

Time-dependent Tonks-Langmuir model is unstable.

We investigate a time-dependent extension of the Tonks-Langmuir model for a one-dimensional plasma discharge with collisionless kinetic ions and Boltzmann electrons. Ions are created uniformly throughout the volume and flow from the center of the discharge to the boundary wall due to a self-consistent, zero-order electric field. Solving this model using a particle-in-cell simulation, we observe coherent low-frequency, long-wavelength unstable ion waves which move toward the boundary with a speed below both the ion acoustic speed and the average ion velocity. The maximum amplitude of the wave potential fluctuations peaks at ≈0.09T_{e} near the wall, where T_{e} is the electron temperature in electron volts. Using linear kinetic theory, we identify this instability as slow ion-acoustic wave modes which are destabilized by the zero-order electric field.

An approach to line-shaped nitrogen plasma production at atmospheric pressure by slot-excited microwave discharge

For large-area surface treatment processing at atmospheric pressure, a one-dimensional line-shaped plasma source using molecular gas discharge excited by a 2.45 GHz microwave was investigated. From the results of three-dimensional microwave simulation, a flat waveguide is proposed to increase the power density for the enhancement of the electric field inside the slot and easy breakdown and sustainment without markedly increasing the input power. A pure N2 plasma of submeter length was produced by a travelling wave of CW microwave power using the flat waveguide with a narrow-gap slot of 30 cm length incorporated into the loop waveguide system to suppress standing waves. The plasma length was increased by increasing the input microwave power from 1.0 to 2.5 kW and its maximum was about 14 cm. The medium gas temperature of 1100 K was measured from the rotational temperature of the N2 second positive band evaluated by optical emission spectroscopy.

One-dimensional plasma sheath model in front of the divertor plates

A new model of the stationary electrostatic plasma sheath in front of divertor plates is developed, which takes into account strong inelastic processes. Using particle-in-cell simulations and analytic estimates it is demonstrated, that the properties of the tokamak divertor plasma sheath can significantly deviate from the properties of the classical sheath model. The most significant deviations are the increased energy flux to the plates and non-monotonic potential and ion velocity profiles in the presheath. Two main reasons for these deviations are identified: strong inelastic collisionality of the plasma presheath and the presence of super-thermal plasma particles originating from the upstream scrape-off layer.

Nonlocal adiabatic theory. II. Nonlinear frequency shift on an electron plasma wave in a multidimensional inhomogeneous plasma

In this article, we provide a general derivation of the nonlinear frequency shift, δω, for a sinusoidal electron plasma wave (EPW) that varies slowly enough for the results derived in Paper I, on the action distribution function, to apply. We first consider the situation when the EPW monotonously grows and then monotonously decays in a homogeneous plasma. In this situation, we show a hysteresis in the wave frequency, which does not converge back to its linear value as the wave decays to small amplitudes. We then address the derivation of δω for an EPW that keeps growing in a one-dimensional (1-D) inhomogeneous plasma. We show that, usually, the frequency shift does not depend only on the local EPW amplitude and wavenumber but also on the whole history of the density variations, as experienced by the wave. In a multidimensional inhomogeneous plasma, the values assumed by δω are usually different from those derived in 1-D because, due to the transverse electron motion, one must account for the hysteresis in δω in addition to plasma inhomogeneity. Hence, unless the EPW keeps growing in a homogeneous one-dimensional plasma, one cannot derive δω a priori as a function of the local wave amplitude and wavenumber. Due to the nonlocality in the action distribution function, δω depends on the whole history of the variations of the EPW amplitude and plasma density.

Influence of gas flow and applied voltage on interaction of jets in a cross-field helium plasma jet array

Atmospheric Pressure Plasma Jet arrays can greatly enhance the treatment area to fulfill the need for large-scale surface processing, while the spatial uniformity of the plasma jet array is closely related to the interactions of the adjacent jets. In this paper, a three-tube one-dimensional (1D) He plasma jet array with a cross-field needle-ring electrode structure is used to investigate the influences of the gas flow rate and applied voltage on the interactions of the adjacent jets through electrical, optical, and fluid measurements. The repulsion of the adjacent plume channels is observed using an intensified charge-coupled device (ICCD) and the influence of the gas flow rate and applied voltage on the electrostatic repulsion force, Coulomb force, is discussed. It is found that electrical coupling, mainly electrostatic repulsion force, exists among the jets in the array, which causes both the divergence of the lateral plumes and the nonlinear changes of the discharge power and the transport charge. The ...

One-dimensional electromagnetic band gap plasma structure formed by atmospheric pressure plasma inhomogeneities

The ability to use plasma columns of pulse discharges in argon at atmospheric pressure to form a one-dimensional electromagnetic band gap structure (or electromagnetic crystal) in the X-band waveguide is demonstrated. We show that a plasma electromagnetic crystal attenuates a microwave propagation in the stopband more than by 4 orders of magnitude. In order to obtain an effective control of the transmission spectrum comparable with a metallic regular structure, the electron concentration in plasma inhomogeneities should vary within the range from 1014 cm−3 to 1016 cm−3, while gas temperature and mean electron energy must be in the range of 2000 K and 0.5 eV, respectively, to lower electron collision frequency around 1010 s−1. We analyze in detail the time evolution response of the electromagnetic crystal according to the plasma parameters for the duration of the discharge. The interest of using atmospheric pressure discharges is to increase the microwave breakdown threshold in discharge volumes, whereby it becomes possible to perform dynamic control of high power microwaves.

Exact Extremal Statistics in the Classical 1D Coulomb Gas.

We consider a one-dimensional classical Coulomb gas of N-like charges in a harmonic potential-also known as the one-dimensional one-component plasma. We compute, analytically, the probability distribution of the position x_{max} of the rightmost charge in the limit of large N. We show that the typical fluctuations of x_{max} around its mean are described by a nontrivial scaling function, with asymmetric tails. This distribution is different from the Tracy-Widom distribution of x_{max} for Dyson's log gas. We also compute the large deviation functions of x_{max} explicitly and show that the system exhibits a third-order phase transition, as in the log gas. Our theoretical predictions are verified numerically.

Multichannel tunable filter properties of 1D magnetized ternary plasma photonic crystal in the presence of evanescent wave

The multichannel tunable filter properties of one-dimensional ternary plasma photonic crystal composed of magnetized plasma and lossless dielectric have been theoretically investigated using transfer matrix method in the microwave region. The proposed filters possess 2N − 2 comb-like sharp resonant peaks also called transmission channels for N > 1 in transmission spectra in the absence and presence of an external magnetic field. Due to the coupling between evanescent waves and propagating modes in plasma and dielectric layers, respectively, 2N − 2 transmission channels are found without the addition of any defect, enabling the structure to work as a multichannel filter. Next, the filter properties can be made tunable by the application of an external magnetic field, i.e., channel frequency can either be red or blue shifted depending upon the orientation of an external magnetic field. The number of channels and their positions can also be modulated by changing the number of periods (N) and the incident angle (θo), respectively, for both transverse electric (TE) and transverse magnetic (TM) modes besides other parameters such as plasma collision frequency, thickness of the plasma layer, plasma frequency, etc.