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We conduct electromagnetic particle simulations to examine the applicability of nonlinear wave growth theory to the generation process of plasmaspheric hiss. We firstly vary the gradient of the background magnetic field from a realistic model to a rather steep gradient model. Under such variation, the threshold amplitude in the nonlinear theory increases quickly and the overlap between threshold and optimum amplitude disappears correspondingly, the nonlinear process is suppressed. In the simulations, as we enlarge the gradient coefficient of the background magnetic field, waves generated near the equator do not grow through propagation. By examining the range of suitable values of inhomogeneity factor S (i.e., $$|S| | S | < 2 ), we find the generation of wave packets is limited to the equatorial region when the background field is steep, showing a good agreement with what is indicated by critical distance in the theory. We then check the dependence of generation of hiss emissions on different hot electron densities. Since the overlap between threshold and optimum amplitude vanishes, the nonlinear process is weakened when hot electron density becomes smaller. In the simulation results, we find similar wave structures in all density cases, yet with different magnitudes. The existence of suitable S values implies that the nonlinear process occurs even at a low level of hot electron density. However, by examining $$J_E$$ J E that closely relates to the wave growth, we find energy conveyed from particles to waves is much limited in small density cases. Therefore, the nonlinear process is suppressed when hot electron density is small, which agrees with the theoretical analysis. Graphical Abstract

Energy accumulation and dissipation play an important role during the entire process of rock failure. Some flaws, such as preexisting holes, will influence energy accumulation and dissipation. In order to investigate the energy evolution of coal specimen with preexisting holes under uniaxial compression through numerical approaches, the particle simulation method was used in numerical simulations. In this paper, the energy evolution of coal specimen was theoretically analyzed, and the influence of different hole arrangement, such as diameter, spacing, angle, and number, on the evolution characteristics of energy was also discussed. At the same time, the arrangement of the artificial boreholes for preventing the rockburst was explored. The results show that, compared with the intact coal specimen, the change of diameter, spacing, angle, and the number of holes weakened the coal specimen’s capacity to store energy and release strain energy. When the diameter, the vertical distance, and relative angle of preexisting holes were 15 mm, 10∼15 mm, and 60°, respectively, the energy storage limit reached optimal value. For arrangement of the artificial boreholes, the diameter, spacing, and angle can be designed on the basis of those optimal values. This study has a guiding significance in designing the arrangement of the artificial boreholes for mitigation of rockburst.

Particle simulation has been widely used in studying plasmas. The technique follows the motion of a large assembly of charged particles in their self-consistent electric and magnetic fields. Plasmons, collective oscillations of the free electrons in conducting media such as metals, are connected to plasmas by very similar physics, in particular, the notion of collective charge oscillations. In many cases of interest, plasmons are theoretically characterized by solving the classical Maxwell’s equations, where the electromagnetic responses can be described by bulk permittivity. That approach pays more attention to fields rather than motion of electrons. In this work, however, we apply the particle simulation method to model the kinetics of plasmons, by updating both particle position and momentum (Newton–Lorentz equation) and electromagnetic fields (Ampere and Faraday laws) that are connected by current. Particle simulation of plasmons can offer insights and information that supplement those gained by traditional experimental and theoretical approaches. Specifically, we present two case studies to show its capabilities of modeling single-electron excitation of plasmons, tracing instantaneous movements of electrons to elucidate the physical dynamics of plasmons, and revealing electron spill-out effects of ultrasmall nanoparticles approaching the quantum limit. These preliminary demonstrations open the door to realistic particle simulations of plasmons.

Purpose This paper covers recent developments and applications of the TOPAS TOol for PArticle Simulation and presents the approaches used to disseminate TOPAS. Materials and methods Fundamental understanding of radiotherapy and imaging is greatly facilitated through accurate and detailed simulation of the passage of ionizing radiation through apparatus and into a patient using Monte Carlo (MC). TOPAS brings Geant4, a reliable, experimentally validated MC tool mainly developed for high energy physics, within easy reach of medical physicists, radiobiologists and clinicians. Requiring no programming knowledge, TOPAS provides all of the flexibility of Geant4. Results After 5 years of development followed by its initial release, TOPAS was subsequently expanded from its focus on proton therapy physics to incorporate radiobiology modeling. Next, in 2018, the developers expanded their user support and code maintenance as well as the scope of TOPAS towards supporting X-ray and electron therapy and medical imaging. Improvements have been achieved in user enhancement through software engineering and a graphical user interface, calculational efficiency, validation through experimental benchmarks and QA measurements, and either newly available or recently published applications. A large and rapidly increasing user base demonstrates success in our approach to dissemination of this uniquely accessible and flexible MC research tool. Conclusions The TOPAS developers continue to make strides in addressing the needs of the medical community in applications of ionizing radiation to medicine, creating the only fully integrated platform for four-dimensional simulation of all forms of radiotherapy and imaging with ionizing radiation, with a design that promotes inter-institutional collaboration.

A Full-Orbit CUDA Solver for particle simulations in plasmas, FOCUS, has been developed. The code follows exact particle trajectories by solving Newton’s equations with the Lorentz force. The code can use fields calculated analytically or numerically and it is also possible to use the information provided by equilibrium reconstruction and transport codes. FOCUS has an elastic collisions module which covers the whole particle energy range in magnetic fusion devices. Moreover, an atomic collision module was also included to simulate the interaction of the test particles with neutral or partially ionized species. Regarding performance, the main feature is that the code runs on GPUs, allowing the simulation of a large number of particles using moderate computational resources. Different versions of the code have been used in several papers. Here we present a complete description of its capabilities, the basis physics included and detailed information about the numerical algorithms employed. Finally, some examples are presented. Fil: Clauser, Cesar Fernando. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Farengo, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Ferrari, Hugo Emilio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

We have conducted a one‐dimensional electromagnetic particle simulation with a parabolic magnetic field to reproduce whistler‐mode hiss emissions in the plasmasphere. We assume a bi‐Maxwellian distribution with temperature anisotropy for energetic electrons injected into the plasmasphere and find that hiss emissions are generated with spectrum characteristics typical of those observed by spacecraft near the magnetic equator. The hiss emissions contain fine structures involving rising tone and falling tone elements with variation in frequencies. The amplitude profile of the spectra agrees with the optimum wave amplitude derived from the nonlinear wave growth theory. The simulation demonstrates that hiss emissions are generated locally near the magnetic equator through linear and nonlinear interactions with energetic electrons with temperature anisotropy. The coherent hiss emissions efficiently scatter resonant electrons of 2.5–80 keV into the loss cone.

The purpose of the present paper is to provide an overview of As ymptotic- Preserving methods for multiscale plasma simulations by ad dressing three sin- gular perturbation problems. First, the quasi-neutral lim it of fluid and kinetic models is investigated in the framework of non magnetized as well as magne- tized plasmas. Second, the drift limit for fluid description s of thermal plasmas under large magnetic fields is addressed. Finally efficient nu merical resolutions of anisotropic elliptic or diffusion equations arising in ma gnetized plasma simu- lation are reviewed.

Particle simulations are able to model behavior of granular materials, but are very slow when large-scale phenomena and industrial applications of granular materials are considered. Even with the most advanced computational techniques, it is not possible to simulate realistic numbers of particles in large systems with complex geometries. Thus, continuum models are more desirable, where macroscopic field variables can be obtained from a micro-macro averaging procedure. However, aspects of microscopic scale are neglected in classical continuum theories (restructuring, geometric non linearity due to discreteness, explicit control over particle properties). The focus of this work is the investigation of elastic and dissipative behavior of isotropic, dense assemblies. In particular, the attention is devoted on the effect of microscopic parameters (e.g. stiffness, friction, cohesion) on the macroscopic response (e.g. elastic moduli, attenuation). The research methodology combines experiments, numerical simulations, theory. One goal is to extract the macroscopic material properties from the microscopic interactions among the individual constituent particles; for simple enough systems this can often be done using techniques from mechanics and statistical physics. While these simplified models can not capture all aspects of technically relevant realistic grains the fundamental physical phase transitions can be studied with these model systems. Complex mixtures with more than one particle species can exhibit enhanced mechanical properties, better than each of the ingredients. The interplay of soft with stiff particles is one reason for this, but requires a more accurate formation of the interaction of deformable spheres. A new multi-contact approach is pro- posed which shows a better agreement between experiments and simulations in comparison to the conventional pair interactions. The study of wave propagation in granular materials allows inferring many fundamental properties of particulate systems such as effective elastic and dissipative mechanisms as well as their dispersive interplay. Measurements of both phase velocities and attenuation provide complementary information about intrinsic material properties. Soft-stiff mixtures, with the same particle size, tested in the geomechanical laboratory, using a triaxial cell equipped with wave transducers, display a discontinuous dependence of wave speed with composition. The diffusive characteristic of energy propagation (scattering) and its frequency dependence (attenuation) are past into a reduced order model, a master equation devised and utilized for analytically predicting the transfer of energy across a few different wavenumber ranges, in a one-dimensional chain.

In this article, a cavity with a frequency of 38GHz is designed. Through numerical calculation and computer simulation, TM31 mode, the dispersion curve, quality factor and S11 parameter of a high frequency structure of 38GHz extended interaction oscillator are studied. S 11 parameter is calculated to find optimum output window size for cold-test experiment. And the results of particle simulation is also shown in this article. Compared with the results of cold cavity, the results of particle simulation are consistent. This research is of great significance for the development of millimeter wave vacuum devices.

In order to clarify the discharge principle of the self-field magnetoplasmadynamic thruster (MPDT), a two-dimensional axisymmetric particle-in-cell/Monte Carlo collision (PIC/MCC) model is proposed. The spatial distribution and the collision characteristics of discharge plasma were calculated using this model. In addition, the influence of the operation parameters on the plasma was analyzed including the voltage and mass flow rate. The effectiveness of the model was verified by comparison to the experimentally induced magnetic field. It was found that the electrons were mainly accelerated by the electric field in the cathode sheath and the electric field shielding effect of plasma was obvious in the bulk plasma region. Due to the pinch effect, the charged particles were constrained near the cathode. The results of the present work implied that the PIC/MCC model provides an approach to investigate the plasma distribution and a kinetic description of particles for the discharge of the self-field MPDT.

© 2018 Elsevier B.V. The long-term macroparticle tracking simulation is computationally challenging but needed in order to study space-charge effects in high intensity circular accelerators. To address the challenge, in this paper, we proposed using a fully symplectic particle-in-cell model for the long-term space-charge simulation. We analyzed the artificial numerical emittance growth in the simulation and suggested using threshold numerical filtering in frequency domain to mitigate the emittance growth in the simulation. We also explored alternative frozen space-charge simulations and observed qualitative agreement with the self-consistent simulations.

The simulative prediction of fiber orientation for injection-molded short fiber-reinforced thermoplastics is an important step in prediction warpage and failure of injection molded parts. There exists a variety of phenomenological macroscopic fiber orientation models, which are computationally very efficient but strongly dependent on phenomenological parameters. This research focuses on a mechanistic fiber orientation model for concentrated short fiber-reinforced thermoplastics. A fully coupled computational fluid dynamics particle simulation is used to estimate the lubrication forces between two fibers in different configurations (angles between fibers, velocities) with varying fiber length and surrounding fluid viscosity. Based on these data, a calibrated lubrication model is developed and implemented in a mechanistic fiber orientation simulation. In addition, the fiber orientation estimated by the enhanced mechanistic fiber model is compared to experimental fiber orientation data obtained with a glass fiber-reinforced thermoplastic industrial grade, which showed an improvement over a simulation that did not include the lubrication force.

Colloidal dispersions have attracted much attention both from academia and industry due to industrial significance and complex dynamic properties. Accordingly, a variety of attempts have been made to understand the complicated physics of colloidal dispersions. Particle dynamics simulation has been playing an important role in exploring colloidal systems as a strong complement to experimental approaches from which it is hard to get exact microscopic information. Our aim is to provide a well-organized and up-to-date guide to particle dynamics simulation of colloidal dispersions. Among diverse particle dynamics simulation techniques, we focus on Brownian dynamics, Stokesian dynamics, multi-particle collision dynamics, and self-consistent particle simulation techniques. First, the concept of the simulation techniques will be described. Then, for each simulation technique, pros and cons are discussed with a broad range of applications, including concentrated hard sphere suspensions and biological systems. It is expected that this article helps to identify and motivate research challenges.

We discuss in detail a recently proposed hybrid particle-continuum scheme for complex fluids and evaluate it at the example of a confined homopolymer solution in slit geometry. The hybrid scheme treats polymer chains near the impenetrable walls as particles keeping the configuration details, and chains in the bulk region as continuous density fields. Polymers can switch resolutions on the fly, controlled by an inhomogeneous tuning function. By properly choosing the tuning function, the representation of the system can be adjusted to reach an optimal balance between physical accuracy and computational efficiency. The hybrid simulation reproduces the results of a reference particle simulation and is significantly faster (about a factor of 3.5 in our application example).

We study the effects of cloud-in-cell sampling and gyroaveraging on random noise in real space (as opposed to the common Fourier space presentation), and show that together, these can reduce the noise by a factor of 3 compared to nearest grid point sampling without gyroaveraging. Hence an order of magnitude less test particles are needed for the given noise level. We derive equations for noise level as a function of Larmor radius and also investigate the effect of gyroaveraging on noise in local gradients. The effect of number of gyropoints on noise is also discussed.

A quasi-neutral blended drift-Lorentz particle model of the field-reversed configuration (FRC) has been developed and implemented in the particle-in-cell code named ANC. A field-aligned mesh and corresponding mesh operations are constructed for solving self-consistent electric fields in FRC geometry. Particle dynamics are described in cylindrical coordinates to allow for cross-separatrix simulation coupling the core and scrape-off layer regions of the FRC. This new model is successfully verified against analytically derived dispersion relations, and FRC turbulence is studied using the blended model for the first time.

Mechanical interactions between flowing and coagulated blood (thrombus) are crucial in dictating the deformation and remodeling of a thrombus after its formation in hemostasis. We propose a fully-Eulerian, three-dimensional, phase-field model of thrombus that is calibrated with existing in vitro experimental data. This phase-field model considers spatial variations in permeability and material properties within a single unified mathematical framework derived from an energy perspective, thereby allowing us to study effects of thrombus microstructure and properties on its deformation and possible release of emboli under different hemodynamic conditions. Moreover, we combine this proposed thrombus model with a particle-based model which simulates the initiation of the thrombus. The volume fraction of a thrombus obtained from the particle simulation is mapped to an input variable in the proposed phase-field thrombus model. The present work is thus the first computational study to integrate the initiation of a thrombus through platelet aggregation with its subsequent viscoelastic responses to various shear flows. This framework can be informed by clinical data and potentially be used to predict the risk of diverse thromboembolic events under physiological and pathological conditions., Author summary Thromboembolism is associated with detachment of small thrombus pieces from the bulk in the blood vessel. These detached pieces, also known as emboli, travel through the blood flow and may block other vessels downstream, e.g., they may plug the deep veins of the leg, groin or arm, leading to venous thromboembolism (VTE). VTE is a significant cause of morbidity and mortality and it affects more than 900,000 people in the United States and result in approximately 100,000 deaths every year. Mechanical interaction between flowing blood and a thrombus is crucial in determining the deformation of the thrombus and the possibility of releasing emboli. In this study, we develop a phase-field model that is capable of describing the structural properties of a thrombus and its biomechanical properties under different blood flow conditions. Moreover, we combine this thrombus model with a particle-based model which simulates the initiation of the thrombus. This combined framework is the first computational study to simulate the development of a thrombus from platelet aggregation to its subsequent viscoelastic responses to various shear flows. Informed by clinical data, this framework can be used to predict the risk of diverse thromboembolic events under physiological and pathological conditions.

This paper proposes a new type of coaxial TM 10,10 mode output cavity with an axial output circuit. Its characteristics of cold cavity are simulated by CST-MWS, and the gap impedance is calculated form equivalent circuit. An 0.3THz coaxial TM 10,10 mode output cavity with ten 20 kV, 0.5A beams is simulated by CST-PIC. The result of particle simulation indicates the average output power of 450W, 3-dB bandwidth of 1.66GHz.

We present a symmetric particle simulation scheme for diffuse fluids based on the Lagrangian Smoothed Particle Hydrodynamics (SPH) model. In our method, the generation of diffuse particles is determined by the entropy of fluid particles, and it is calculated by the velocity difference and kinetic energy. Diffuse particles are generated near the qualified diffuse particle emitters whose diffuse material generation rate is greater than zero. Our method fits the laws of physics better, as it abandons the common practice of adding diffuse materials at the crest empirically. The coupling between diffuse materials and fluid is a post-processing step achieved by the velocity field, which enables the avoiding of the time-consuming process of cross finding neighbors. The influence weights of the fluid particles are assigned based on the degree of coupling. Therefore, it improved the accuracy of the diffuse particle position and made the simulation results more realistic. The approach is appropriate for large scale diffuse fluid, as it can be easily integrated in existing SPH simulation methods and the computational overhead is negligible.

This paper will describe a formalism for using correlation functions between different grid cells as the basis for determining coarse-grained hydrodynamic equations for modeling the behavior of mesoscopic fluid systems. Configurations from a molecular dynamics simulation or other atomistic simulation are projected onto basis functions representing grid cells in a continuum hydrodynamic simulation. Equilibrium correlation functions between different grid cells are evaluated from the molecular simulation and used to determine the evolution operator for the coarse-grained hydrodynamic system. The formalism is demonstrated on a discrete particle simulation of diffusion with a spatially dependent diffusion coefficient. Correlation functions are calculated from the particle simulation and the spatially varying diffusion coefficient is recovered using a fitting procedure.

International audience; The interaction of the solar wind with the terrestrial magnetosphere is analyzed with the help of three-dimensional (3-D) global, full-electromagnetic particle-in-cell (PIC) simulations, in the configuration where the interplanetary magnetic field (IMF) is steadily northward. The present study is mainly focused on the cusp region and associated particle momenta dynamics. Within the present context and to the best of our knowledge, this work represents the first numerical simulation for analyzing the cusp dynamics using a fully self-consistent 3-D kinetic and electromagnetic approach. The main goals of the study are the following: (i) to retrieve the main known features of the cusp to validate the use of 3-D PIC “global” simulations, (ii) to compare with previous results obtained with 3-D MHD simulations, (iii) to create an updated global view of the cusp based on use of 3-D PIC simulation, which cannot be obtained from a MHD approach, and (iv) to compare with statistical results from the Cluster mission. In particular, the stagnant exterior cusp (SEC) identified in previous statistical analysis of experimental data is retrieved, and it is possible to more precisely define the edges of the SEC region. In addition, we will focus on cusp features recently observed by the Cluster mission, for example, the Alfvén Transition Layer or ATL and on the features not reproduced by either MHD or the hybrid approach, which have been used to characterize the outer edges of the cusp more clearly.

We have developed a 2.5-dimensional electromagnetic particle simulation code using the particle-in-cell (PIC) method to investigate electromagnetic phenomena that occur in space plasmas. Our code is based on the leap-frog method and the centered difference method for integration and differentiation of the governing equations. We adopted the relativistic Buneman-Boris method to solve the Lorentz force equation and the Esirkepov method to calculate the current density while maintaining charge conservation. Using the developed code, we performed test simulations for electron two-stream instability and electron temperature anisotropy induced instability with the same initial parameters as used in previously reported studies. The test simulation results are almost identical with those of the previous papers.

As quantitative biologists get more measurements of spatially regulated systems such as cell division and polarization, simulation of reaction and diffusion of proteins using the data is becoming increasingly relevant to uncover the mechanisms underlying the systems. Spatiocyte is a lattice-based stochastic particle simulator for biochemical reaction and diffusion processes. Simulations can be performed at single molecule and compartment spatial scales simultaneously. Molecules can diffuse and react in 1D (filament), 2D (membrane), and 3D (cytosol) compartments. The implications of crowded regions in the cell can be investigated because each diffusing molecule has spatial dimensions. Spatiocyte adopts multi-algorithm and multi-timescale frameworks to simulate models that simultaneously employ deterministic, stochastic, and particle reaction-diffusion algorithms. Comparison of light microscopy images to simulation snapshots is supported by Spatiocyte microscopy visualization and molecule tagging features. Spatiocyte is open-source software and is freely available at http://spatiocyte.org .

We report where and how ions are accelerated in the proximity of earthward propagating dipolarization fronts (DFs) in the magnetotail during a magnetospheric substorm on February 15, 2008. Two DFs were observed by multiple THEMIS spacecraft in the near-Earth magnetotail (∼−10 Re). We studied the ion dynamics associated with these DFs by comparing observed results with large scale kinetic (LSK) simulation results. The LSK simulation reproduced the sudden ion energy flux enhancement concurrent with the arrival of the DF at the satellite locations. We found that ions can be accelerated to more than 100 keV energy at the DF. These ions were initially non-adiabatically accelerated near magnetic reconnection site and then still non-adiabatically accelerated at the DF structure.

Particle simulation is a powerful method to study the dynamical behavior of fluids. In this method, fluids are modeled as systems of small particles with the proper physical properties. A result of the particle simulation is often obtained as largescale 3D point data. In this paper, we propose to visualize the data by using the particle-based rendering, which we recently proposed. The key idea is to utilize the 3D points directly as the rendering primitives, which we call “particles”. Based on this scheme, we can realize quick and high-quality visualization of large-scale particle simulations. Moreover, we can easily superpose (fuse) objects surrounding or underlying the simulated fluid. It is also possible to fuse multiple physical values, for example, velocity and vorticity of the simulated fluid. We demonstrate our scheme by applying it to a large-scale tsunami run-up simulation for the Great East Japan Earthquake that occurred in March 2011.

The characteristic feature of a “horn-shaped velocity distribution” in magnetic reconnection in the presence of a guide field is investigated by means of simulation and theory. Particle simulations show that a horn-shaped velocity structure is formed in the downstream, concomitant with a ring-shaped velocity distribution studied in the preceding works. The theory which explains the motion of ions responsible for the horn-shaped structure is constructed as an extension of the basic theory for the ring-shaped structure. In the extended theory, ions are accelerated in the inflow direction by an electrostatic field in the separatrix, and thus the gyration speed of such ions in the downstream is larger than that for the basic theory. Test particle simulations confirm that some ions behave as in the extended theory and form the horn-shaped velocity structure.

The present paper covers the numerical prediction of the propagation and run-up of a solitary wave over non-flat seabed with various slope angles using a refined MPS (moving particle simulation) method. In the refined method, the corrected gradient model, new staggered divergence-free model, moving-particle wall boundary treatment, and the sub-particle scale turbulence model are applied to obtain more stable and precise results. The simulation results by the developed method are compared with experimental results, and both results were in good agreement. Especially, it can be seen that the complicated and fully-nonlinear behavior of the free-surface motion during the turbulent processes of build-up, break-down, and overturning of the waves are well reproduced by the developed method.

In this paper, the design and particle simulation of a Ka-band stagger tuned gyro-twystron amplifier is presented. The concept of stagger tuning in gyro-twystron improves the bandwidth along with high RF output power which is suitable for radar application. The complete amplifier structure is modelled in “CST particle studio” for studying the beam wave interaction behaviour. The PIC simulation predicted a peak output power of ∼ 135kW for the beam parameters of 80 kV, 3A with a velocity spread of 5%. The electronic efficiency has been obtained as 56%, and the saturated gain of 57 dB. The stagger technique enhanced the bandwidth by ∼ 2% about the centre frequency.

We present enhancements and new capabilities of the Physalis method for simulating disperse multiphase flows using particle-resolved simulation. The current work enhances the previous method by incorporating a new type of pressure-Poisson solver that couples with a new Physalis particle pressure boundary condition scheme and a new particle interior treatment to significantly improve overall numerical efficiency. Further, we implement a more efficient method of calculating the Physalis scalar products and incorporate short-range particle interaction models. We provide validation and benchmarking for the Physalis method against experiments of a sedimenting particle and of normal wall collisions. We conclude with an illustrative simulation of 2048 particles sedimenting in a duct. In the appendix, we present a complete and self-consistent description of the analytical development and numerical methods.

The gyrokinetic full 5D particle distribution code ELMFIRE has been extended to simulate circular tokamak plasmas from the magnetic axis to the limiter scrape-off-layer. The predictive power of the code in the full-torus configuration is tested via its ability to reproduce experimental steady-state profiles in FT-2 ohmic L-mode plasmas. The results show that the experimental profile solution is not reproduced numerically due to the difficulty of obtaining global power balance. This is verified by cross-comparison of ELMFIRE code versions, which shows also the impact of boundary conditions and grid resolution on turbulent transport.

A time-dependent particle code has been developed to simulate the motion and changing regularity of particles in multi-beam traveling wave tube. Magnetic focusing and interaction models of multi-beam traveling tube were established, and static magnetic field was calculated. The process of bunching particles by periodic permanent magnetic focusing system and beam-wave interaction was also simulated. The results show that particle simulation can really reflect the motion of particles in multi-beam traveling wave tube, which can provide some references for particle study of traveling wave tube.

Simple scaling laws for the design parameters of plasma wakefield accelerators were obtained using a theoretical model, which were confirmed via particle simulation studies. It was found that the acceleration length was given by Δ x = 0.804 λ p / ( 1 − β g ) , where λ p is the plasma wavelength and β g c the propagation velocity of the ion cavity. The acceleration energy can also be given by Δ E = ( γ m − 1 ) m c 2 = 2.645 m c 2 / ( 1 − β g ) , where m is the electron rest mass. As expected, the acceleration length and energy increase drastically as β g approached unity. These simple scaling laws can be very instrumental in the design of better-performing plasma wakefield accelerators.