Electromagnetic Particle-in-cell Research Articles

3D electromagnetic PIC simulations of relativistic electron pulse injections from spacecraft

Relativistic electron beam accelerators (5 MeV, 0.1 A) can now be flown on spacecraft. Injection from low-Earth-orbit into the atmosphere makes it possible to perform active perturbation experiments in the 40–60 km altitude range. These include modification of the atmospheric electric potential structure over thunderstorm regions and the possible stimulation of high-altitude-lightning, as well as studies of relativistic electron precipitation effects on chemical reaction paths. In this paper, the initial stage of the beam injection process is simulated by a fully electromagnetic and relativistic Particle-in-Cell (PIC) code. The self-consistent implementation of electric charging of a spacecraft structure in an electromagnetic code is demonstrated, and beam propagation dynamics is explored for a range of beam to ambient plasma densities. It is shown that the combined effects of ambient plasma and beam self-fields may allow propagation in the ion-focused regime and that this regime primarily is expected for relativistic beams.

Geospace Environmental Modeling (GEM) Magnetic Reconnection Challenge

The Geospace Environmental Modeling (GEM) Reconnection Challenge project is presented and the important results, which are presented in a series of companion papers, are summarized. Magnetic reconnection is studied in a simple Harris sheet configuration with a specified set of initial conditions, including a finite amplitude, magnetic island perturbation to trigger the dynamics. The evolution of the system is explored with a broad variety of codes, ranging from fully electromagnetic particle in cell (PIC) codes to conventional resistive magnetohydrodynamic (MHD) codes, and the results are compared. The goal is to identify the essential physics which is required to model collisionless magnetic reconnection. All models that include the Hall effect in the generalized Ohm's law produce essentially indistinguishable rates of reconnection, corresponding to nearly Alfvénic inflow velocities. Thus the rate of reconnection is insensitive to the specific mechanism which breaks the frozen‐in condition, whether resistivity, electron inertia, or electron thermal motion. The reconnection rate in the conventional resistive MHD model, in contrast, is dramatically smaller unless a large localized or current dependent resistivity is used. The Hall term brings the dynamics of whistler waves into the system. The quadratic dispersion property of whistlers (higher phase speed at smaller spatial scales) is the key to understanding these results. The implications of these results for trying to model the global dynamics of the magnetosphere are discussed.

Does stochasticity due to whistler mode wave coupling persist in self-consistent systems?

Previous studies suggest that interactions between a single electron and two oppositely directed, whistler mode waves propagating parallel to a constant background magnetic field can be regarded as a candidate source for phase space diffusion leading to dissipation procedures in collisionless astrophysical plasmas. In this paper the above interaction process is examined self-consistently. We make direct comparison between the dynamics predicted from single particle orbits and that extracted from electron motion in 1D electromagnetic particle in cell (PIC) simulations. By this means we are able to establish that strong phase space diffusion due to chaos occurs in collisionless plasmas when treated fully self-consistently, and therefore may be an important mechanism for irreversibility in astrophysical plasmas.

Three-dimensional deformable-grid electromagnetic particle-in-cell for parallel computers

We describe a new parallel, non-orthogonal-grid, three-dimensional electromagnetic particle-in-cell (EMPIC) code based on a finite-volume formulation. This code uses a logically Cartesian grid of deformable hexahedral cells, a discrete surface integral (DSI) algorithm to calculate the electromagnetic field, and a hybrid logical–physical space algorithm to push particles. We investigate the numerical instability of the DSI algorithm for non-orthogonal grids, analyse the accuracy for EMPIC simulations on non-orthogonal grids, and present performance benchmarks of this code on a parallel supercomputer. While the hybrid particle push algorithm has a second-order accuracy in space, the accuracy of the DSI field solve algorithm is between first and second order for non-orthogonal grids. The parallel implementation of this code, which is almost identical to that of a Cartesian-grid EMPIC code using domain decomposition, achieved a high parallel efficiency of over 96% for large-scale simulations.

A new guiding centre PIC scheme for electromagnetic highly magnetized plasma simulation

A new implicit fully electromagnetic particle in cell (PIC) method is presented in which the full ion dynamic and all the electron guiding centre drifts of a highly magnetized plasma are retained. We show that the electron drifts do not have to be described explicitly, and that they can be simulated using a simple but efficient linear direct implicit method. Tests and simulations using the new scheme are presented.

Charge compensated ion beam propagation in a reactor sized chamber

Final ion propagation in the space charge compensated scheme (ITEP) is contrasted to Hylife II scenario. A fully electromagnetic particle in cell–Monte Carlo code (PIC–MCC) is considered for the ballistic transport of intense ion beams in a reaction chamber field with Flibe gas surrounding a pellet with a thermonuclear fuel in it. For the latter, we identify a partial beam neutralization only through electron background. The former displays an acceptable focusing on the pellet. The background electron temperature has a significant influence on beam minimum radius. Transverse emittance is given specific attention.

Simulation of ion extraction from laser-induced plasma by electromagnetic fields

The particle-in-cell (PIC) method is extended to allow for particle elastic collisions through the use of the Langevin equation. The one-dimensional, in cylindrical space coordinates, and three-dimensional in velocity coordinates (1D3V), electromagnetic PIC model is used to simulate the dynamics of a plasma produced in the system of two coaxial cylinders by selective laser photoionization in external fields. The electromagnetic fields and the plasma dynamics are solved in a self-consistent manner. Elastic electron–atom, electron–ion, and charge exchange collisions are included in the model. The extraction of ions from the weakly collisional plasma by the electrostatic, crossed electrostatic, and magnetic (E×H), rf, and alternating magnetic fields have been explored to compare the characteristics of various extractors relevant to atomic vapor laser isotope separation (AVLIS).

Modeling the electron heating in a compact electron cyclotron resonance ion source

An electromagnetic particle-in-cell (PIC) model and a guiding-center particle model are developed and used to model a compact electron cyclotron resonance (ECR) plasma source. The finite-difference time-domain technique is used to model the microwave fields which excite the plasma at 2.45 GHz. The PIC technique is used to model the dynamics of the electrons in the plasma. The electromagnetic fields and the plasma dynamics are solved in a self-consistent manner. The ECR heated electrons are confined to magnetic field lines and subsequently make multiple passes through ECR regions experiencing both increases and decreases in energy. The distribution function of these energy changes is determined from the electromagnetic PIC model and used in a guiding-center particle model. The longer time scale collisional phenomenon in the plasma is modeled using this guiding-center particle model. A compact ECR plasma source used for the generation of ions for materials processing is simulated. This source has a plasma size of 3.6 cm in diameter and 3 cm in height.

Body-fitted electromagnetic PIC software for use on parallel computers

This paper describes the algorithm and implementation issues for the three-dimensional body-fitted Particle-In-Cell (PIC) software suite 3DPIC for modelling the time evolution of interactions between electromagnetic (EM) fields and flows of relativistic charged particles. 3DPIC is applicable to EM calculations in complex geometries where displacement fields are important, and was developed specifically for microwave device modelling. A description is given of the physical model, the numerical scheme and the software. The software was designed to run efficiently on both serial and distributed-memory parallel computers. The performance achieved by the software on parallel computers demonstrates the potential of this code for large scale time-dependent electromagnetic and electrodynamic calculations.

Three-dimensional electromagnetic PIC model of a compact ECR plasma source

A three-dimensional electromagnetic particle-in-cell (PIC) model is developed and used to model a compact ECR plasma source. The finite-difference time-domain (FDTD) technique is used to model the microwave fields which excite the plasma at 2.45 GHz. The PIC technique is used to model the dynamics of both the electrons and ions in the plasma. The grid structure used is constructed using the cylindrical coordinate system. Techniques which permit stable numerical solutions in the cylindrical coordinate system are developed and described. The electromagnetic fields and the plasma dynamics are solved in a self-consistent manner. A compact ECR (electron cyclotron resonance) plasma source used for the generation of ions for materials processing is simulated. This source has a plasma size of 3.6 cm in diameter and 3 cm in height. Simulation results of microwave power absorption, plasma potential, and microwave electric fields are presented. Distributed computing techniques are explored to handle the large computer memory requirements and the long computer simulation times associated with the three-dimensional particle-in-cell plasma model. >

Performance of a particle‐in‐cell plasma simulation code on the BBN TC2000

AbstractThe BBN TC2000 is a multiple instruction, multiple data (MIMD) machine that combines a physically distributed memory with a logically shared memory programming environment using the unique Butterfly switch. Particle‐in‐cell (PIC) plasma simulations model the interaction of charged particles with electric and magnetic fields. This paper describes the implementation of both a 1‐D electrostatic and a 2 1/2‐D electromagnetic PIC (particle‐in‐cell) plasma simulation code on a BBN TC2000. Performance is compared to implementation of the same code on the shared memory Sequent Balance 21000.