Plasma-Chemical Processes of the Production of Nitrogen Oxides and Ozone in Electron Beam Plasma and Their Influence on Radiation Corrosion of Metals

A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas. We show here the formation of the multi-layer structure of the relativistic electron beam in the plasma due to the different betatron frequency from the beam front to the beam tail. Meanwhile, the nonuniformity of the longitudinal wakefield is the essential reason for the multi-layer structure formation in beam phase space. The influences of beam parameters (beam radius and transverse density profile) on the formation of the multi-layer structure and collective stopping in background plasmas are also considered.

The nonlinear stage in the development of a resistive hose instability of a highcurrent relativistic electron beam in a finite-conductivity plasma has been studied in the rigid-beam model. The attenuation of the force of the interaction of the beam with the magnetic field of the total current for large beam displacements is shown to result in the stabilization of the instability. The stabilization time and the amplitudes of the oscillations in the saturation regime are determined as functions of the parameters of the beam in the plasma.

This paper studies the self-consistent interactions between whistler envelope solitons and electron beams in inhomogeneous plasmas, using a Hamiltonian model of wave-particle interaction where nonlinear equations describing the dynamics of whistler and ion acoustic waves and including a beam current term are coupled with Newton equations. It allows describing the parallel propagation of narrowband whistlers interacting with arbitrary particle distributions in irregular plasmas. It is shown that the whistler envelope soliton does not exchange energy with all the resonant electrons as in the case of whistler turbulence but mostly with those moving in its close vicinity (locality condition), even if the downstream particle distribution is perturbed. During these interactions, the soliton can either damp and accelerate particles, or absorb beam energy and cause electron deceleration. If the energy exchanges are significant, the envelope is deformed; its upstream front can steepen, whereas oscillations can appear on its downstream side. Weak density inhomogeneities as the random fluctuations of the solar wind plasma have no strong impact on the interactions of the whistler soliton with the resonant particles.

The long-distance stable transport of relativistic electron beams (REBs) in plasmas is studied by full three-dimensional particle-in-cell simulations. Theoretical analysis shows that the beam transport is mainly influenced by three transverse instabilities, where the excitation of self-modulation instability, and the suppression of the filamentation instability and the hosing instability are important to realize the beam stable transport. By modulating the transport parameters such as the electron density ratio, the relativistic Lorentz factor, the beam envelopes and the density profiles, the relativistic bunches having a smooth density profile and a length of several plasma wave periods can suppress the beam-plasma instabilities and propagate in plasmas for long distances with small energy losses. The results provide a reference for the research of long-distance and stable transport of REBs, and would be helpful for new particle beam diagnosis technology and space active experiments.

Plasma-based acceleration is being considered as the basis for building a future linear collider. Nonlinear plasma wakefields have ideal properties for accelerating and focusing electron beams. Preservation of the emittance of nano-Coulomb beams with nanometer scale matched spot sizes in these wakefields remains a critical issue due to ion motion caused by their large space charge forces. We use fully resolved quasistatic particle-in-cell simulations of electron beams in hydrogen and lithium plasmas, including when the accelerated beam has different emittances in the two transverse planes. The projected emittance initially grows and rapidly saturates with a maximum emittance growth of less than 80% in hydrogen and 20% in lithium. The use of overfocused beams is found to dramatically reduce the emittance growth. The underlying physics that leads to the lower than expected emittance growth is elucidated.

The development and nonlinear saturation of two-stream instability of a warm nonrelativistic electron beam in a cold plasma are investigated numerically in the framework of a one-dimensional model. It is shown that, for a sufficiently large velocity spread of the electron beam, instability develops and saturates according to a universal law, the wave phase velocity remains the same in the saturation stage, and the maximum field is somewhat lower than that predicted by classical estimates and depends in a different way on the growth rate. The damping of plasma oscillations not only changes the instability growth rate, but also substantially decreases the maximum wave field.

An analytical and numerical study is presented herewith to get an insight into the excitation of forward and backward waves caused by an intense relativistic electron beam in a rippled wall plasma filled waveguide with weak modulation. The numerical results of growth rate are derived in the case of weak modulation at kz=π/z0 (the π point). Numerical results also show that no excitation of waves takes place if relativistic factor of the beam γ<(1+μ20s/R20k20)1/2. For γ≳(1−μ20s/R20k20)−1/2, the beam excites both forward and backward waves, and only forward waves if (1+μ20s/R20k20)1/2<γ< (1−μ20s/R20k20)−1/2. The dependence of the frequency of the generated forward waves on beam energy is also studied numerically and the results are compared with those of the experiment [IEEE Trans. Plasma Sci. PS-18, 490 (1990)]. The effect of corrugation depth of rippled wall plasma filled backward wave oscillator (BWO) on minimum frequency generated is also studied.

The tensor of permittivity for the system “electron beam - plasma of the interplanetary space” is derived in the approximation of geometrical optics. The problem is one-dimensional; all parameters such as density of the beam and of the solar wind plasma, and the induction of the interplanetary magnetic field are assumed to be dependent only on the distance to the Sun. The beam is generated by an active region during a solar flare, and it is a source of radio bursts of type III in the interplanetary space. The tensor of permittivity was obtained to close field equations by a material equation. On the basis of these equations it becomes possible to study theoretically the amplitude-frequency characteristics of the radio bursts as disturbances of the above-described beam-plasma system.

We present comprehensive two-dimensional (2D) particle-in-cell (PIC) simulations on the transport of a relativistic electron beam in a plasma in the context of fast ignition fusion. The 2D PIC simulations are performed by constructing two different simulation planes and have shown the complete stabilization and destabilization of the Weibel instability due to the beam temperature and background plasma collisions, respectively. Some three-dimensional PIC simulation results on the filamentary structures are also shown thereby further shedding light on the filamentation of the electron beam in plasmas. The linear growth rates of fastest growing mode in the beam-plasma system are compared with a theoretical model developed and are found in good agreement with each other.

Electron acoustic dressed solitons in an electron-beam plasma with higher-order contributions

Interplay among ozone and nitrogen oxides in air plasmas: Rapid change in plasma chemistry

The ozone production in the troposphere has been studied by means of a zonally averaged model which consists of a two‐dimensional transport model, a description of the emissions, wet and dry deposition, and chemical processes of importance for the ozone production in the troposphere. The transport model describes a closed circulation in the meridional plane below 10 hPa and has a resolution and a numerical solution which compares favorable with earlier two‐dimensional studies. The transport model also takes into account the fast vertical mixing in convective clouds and in frontal circulation. The production of nitrogen oxides by lightning has been coupled to the convection parameterization by assuming that the nitrogen oxides are transported vertically in the thunder clouds and released at the altitudes where boundary layer air entrained in the convective cells is released. Comparisons with observations indicate that the model is able to reproduce the seasonal variation of ozone in the meridional plane quite realistically. The calculated distributions of the chemical species which determine tropospheric ozone also compare well with measurements. The model estimated an annually averaged production of ozone in the troposphere over the northern hemisphere of 16.6×1010 molecules/cm2/s and over the southern hemisphere of 5.1×1010 molecules/cm2s. The annually and globally averaged dry deposition is 14.9×1010 molecules/cm2/s, and the corresponding injection from the stratosphere is 4.1×1010 molecules/cm2/s. A 50% reduction of the man‐made emissions from the industrialized society of nitrogen oxides resulted in a reduction in the ozone production of 2.9×1010 molecules/cm2/s in the lower troposphere over the northern hemisphere during the period of maximum photochemical production, June–August. The corresponding production decrease due to a 50% reduction of the emissions of volatile organic compounds and carbon monoxide from the same source, however, was 1.6×1010 molecules/cm2/s. Elsewhere, the effects of reductions are less significant due to smaller influence of man‐made emissions.

This study presented a quantitative evaluation of the performance of a low power miniaturized SDBD source for the production of ozone and nitrogen oxides as benchmarks of long-lived RONS. The effects of varying oxygen and humidity on the trend of the production efficiency are investigated. The oxygen content and the humidity had no noticeable effect on the total power consumed, but their level in the feeding gas has a strong impact on the production of NxOy. It is found also that there is an optimum level of the oxygen content and the humidity for the production of NO2 and N2O. The analysis of the results indicated that the nitrogen excited species, especially $${\text{N}}_{2 } \left( {A^{3} \varSigma_{u}^{ + } } \right)$$ and N(2D) play vital roles in the production of the nitrogen oxides, particularly the NO, which considered as the main source for the other NxOy in the present system. Interestingly, it is found that the humidity has a positive effect on the NO2 production, while it has a negative effect on the N2O and O3, which implied that the present SDBD is a strong oxidizer for the formed NO. The rise in the gas temperature in the present SDBD was negligible and has no effect on the production of nitrogen oxides, while the temperature of the plasma channel might affect the RONS production efficiency. Investigating the production mechanisms and the energy efficiency, of the formed nitrogen oxides, unravels for the first time the performance of the SDBD for nitrogen fixation.

The annular electron beam has significant practical potential in high-energy physics and condensed matter physics, which can be used for edge-enhancement electron imaging, collimation of antiprotons in conventional linear accelerators, acceleration of positively particles like positrons, structured x-ray generation, and manipulation of nanomaterials. The quality of an annular electron beam depends on its energy, flux, and topology. In this article, we study the transport characteristics of the annular electron beam in a plasma medium and propose a scheme to modify it. According to our theory and full three-dimensional LAPINS simulations, we have found that the self-generated magnetic field focuses the incident annular electron beam, enabling the adjustment of its annular width (AW). In addition, the annular electron beam, endowed with angular momentum (AM), exhibits contrasting transport characteristics compared to an annular electron beam without AM. The former requires an external magnetic field to ensure stable transportation in the plasma. Under the influence of this magnetic field, the radius of the annular electron beam can oscillate periodically, with the direction of change whether increasing or decreasing dependent on the field's strength. In this case, the radius of the annular electron beam will be affected by the external magnetic field and allows for the simultaneous adjustment of its radius and AW, significantly broadening its application range.

A model for collective relaxation of high-power relativistic electron beams in plasmas is proposed, which describes beam-plasma interaction in the regime when amplitudes of unstable waves are large enough to trap beam electrons. The distinctive feature of this regime is that the power lost by beam electrons as they interact with exited wave packets weakly depends on the energy of these packets. This makes the model insensitive to the nature of nonlinear processes in plasma, which are responsible for saturation of the beam instability. The model is thus rather universal and suitable for quantitative comparison with the experimental data. The predicted profiles of energy release along the plasma column are in a good quantitative agreement with the ones measured at various experimental facilities.