In this review we describe a transient type of gas discharge which is commonly called streamer discharge, as well few related phenomena in pulsed discharges. Streamers are propagating ionization fronts with self-organized field enhancement at their tips that can appear gases (or close to) atmospheric pressure. They the precursors other discharges like sparks and lightning, but they also occur for example corona reactors or plasma jets used variety chemical purposes. When enough space...

Abstract We report on the development of MPI-AMRVAC version 2.0, which is an open-source framework for parallel, grid-adaptive simulations hydrodynamic and magnetohydrodynamic (MHD) astrophysical applications. The now supports radial grid stretching in combination with adaptive mesh refinement (AMR). advantages this combined approach are demonstrated one-dimensional, two-dimensional, three-dimensional examples spherically symmetric Bondi accretion, steady planar Bondi–Hoyle–Lyttleton flows,...

We present an open-source plasma fluid code for 2D, cylindrical and 3D simulations of streamer discharges, based on the Afivo framework that features adaptive mesh refinement, geometric multigrid methods Poisson's equation, OpenMP parallelism. describe numerical implementation a model drift-diffusion-reaction type, combined with local field approximation. Then we demonstrate its functionality long positive streamers in nitrogen undervolted gaps, using three examples. The first example shows...

We present and compare six simulation codes for positive streamer discharges from different research groups. Four groups use a fully self-implemented code two make of COMSOL Multiphysics®. Three test cases are considered, in which axisymmetric streamers simulated dry air at 1 bar 300 K an undervolted gap. All the same fluid model with transport coefficients. The first case includes relatively high background density electrons ions without photoionization. When each group uses their standard...

We investigate how photoionization, electron avalanches and space charge affect the inception of nanosecond pulsed discharges. Simulations are performed with a 3D PIC-MCC (particle-in-cell, Monte Carlo collision) model adaptive mesh refinement for field solver. This model, whose source code is available online, described in first part paper. Then we present simulation results needle-to-plane geometry, using different nitrogen/oxygen mixtures at atmospheric pressure. In these non-local...

We compare relativistic particle integrators commonly used in plasma physics showing several test cases relevant for astrophysics. Three explicit pushers are considered, namely the Boris, Vay, and Higuera-Cary schemes. also present a new fully implicit integrator that is energy conserving. Furthermore, method based on guiding center approximation included. The algorithms described such they can be readily implemented magnetohydrodynamics codes or Particle-in-Cell codes. Our comparison...

A method is presented to include irregular domain boundaries in a geometric multigrid solver. Dirichlet boundary conditions can be imposed on an defined by level set function. Our implementation employs quadtree/octree grids with adaptive refinement, cell-centered discretization and pointwise smoothing. Boundary locations are determined at subgrid resolution performing line searches. For grid blocks near the interface, custom operator stencils stored that take interface into account. block...

Modeling individual free electrons can be important in the simulation of discharge streamers. Stochastic fluctuations electron density accelerate branching In negative streamers, energetic even 'run away' and contribute to processes such as terrestrial gamma-ray flashes. To track energies locations single relevant regions, we have developed a 3D hybrid model that couples particle for region high fields low densities with fluid rest domain. Here validate our on (super-)particle streamers...

Streamer discharges are a primary mode of electric breakdown in thunderstorms and high voltage technology; they generally believed to grow along field lines. However, we here give experimental numerical evidence that streamers can propagate nearly perpendicularly the background field. These guided by pre-ionization is orders magnitude lower than ionization density streamer channel, hardly affecting Positive could be nitrogen with 0.5% oxygen or less, but not air. This observation also tests...

Because positive streamers propagate opposite to the electron drift velocity, their growth not only depends on local electric eld but also density ahead of them.We have recently demonstrated importance this density, by showing that could be guided weak preionization from a laser.Here, we study streamer guiding in nitrogenoxygen mixtures more detail, better understand propagation streamers.First, conditions required for are investigated, both experimentally and with three-dimensional...

We evaluate the performance of three plasma fluid models: first order reaction-drift-diffusion model based on local field approximation; second energy approximation and a recently developed high by Dujko et al (2013 J. Phys. D 46 475202) review we briefly discuss their derivation, underlying assumptions type transport data they require. Then compare these models to particle-in-cell/Monte Carlo (PIC/MC) code, using 1D test problem. The tests are performed in neon nitrogen at standard...

With mass spectrometry imaging (MSI) on tissue microarrays (TMAs) a large number of biomolecules can be studied for many patients at the same time, making it an attractive tool biomarker discovery. Here we investigate whether lymph node metastasis predicted from MALDI-MSI data. Measurements are performed TMAs and then filtered based spectral intensity percentage tumor cells, after which resulting data 122 is further preprocessed. We assume differences between with without expressed in...

We investigate the dynamics of negative surface discharges in air through numerical simulations with a 2D fluid model. A geometry consisting flat dielectric embedded between parallel-plate electrodes is used. Compared to streamers bulk gas, are observed have higher electron density, electric field and propagation velocity. On other hand, their maximum velocity lower than for positive streamers. In our simulations, slower larger relative permittivity. Negative charge accumulates on when...

We compare simulations and experiments of single positive streamer discharges in air at 100 mbar, aiming toward model validation. Experimentally, streamers are generated a plate–plate geometry with protruding needle. able to capture the complete time evolution reproducible single-filament ns gate-time camera. A 2D axisymmetric drift-diffusion-reaction fluid is used simulate under conditions closely matching those experiments. Streamer velocities, radii light emission profiles compared...

We study negative streamers in ambient air using a 2D axisymmetric fluid model. Depending on the background electric field, we observe accelerating, steady and fading streamers. Fading occurs low fields, when lose their field enhancement velocities become comparable to maximal electron drift velocities. Our focus is propagation mode, during which streamer properties like radius velocity hardly change. However, this mode unstable, sense that small change conditions leads acceleration or...

In this paper, we address two main topics: steady propagation fields for positive streamers in air and streamer deceleration below the field. We generate constant-velocity with an axisymmetric fluid model, by initially adjusting applied voltage based on velocity. After initial transient, observe velocities of $3\times10^4$ m/s to $1.2\times10^5$ m/s, during which properties background field do not change. This mode is fully stable, sense that a small change or eventually leads acceleration...

Streamer discharges are the primary mode of electric breakdown air in lightning and high voltage technology. channels branch many times, which determines developing tree-like discharge structure. Understanding these branched structures is for example important to describe streamer coronas research. We simulate branching positive streamers using a 3D fluid model where photoionization included as discrete stochastic process. The probability morphology good agreement with dedicated experiments....

We present a computational framework for simulating filamentary electric discharges, in which channels are represented as conducting cylindrical segments. The requires model that predicts the position, radius, and line conductivity of at next time step. Using this information, on numerical mesh is updated, new potential computed by solving variable-coefficient Poisson equation. A parallel field solver with support adaptive refinement used, provides Python interface easy experimentation....

Using electric field induced second harmonic generation (E-FISH), we performed direction-resolved absolute measurements on single-channel streamer discharges in 70 mbar (7 kPa) air with 0.2 mm and 2 ns resolutions. In order to obtain the (local) field, developed a deconvolution method taking into account phase variations of E-FISH. The acquired distribution shows good agreement simulation results under same conditions, direction, magnitude, shape. This is first time that E-FISH applied...

Abstract The growth of streamer discharges is determined at their heads, for individual streamers as well in collective phenomena, such trees or coronas bursts ahead lighting leaders. Some properties the velocity $v$ and radius $R$ now can be measured quite well, but this very challenging others maximal electric field, charge content head degree chemical excitation ionization channel. Here we develop, test evaluate a macroscopic approximation positive heads air that relates to each other. In...

Abstract We study how the choice of input data affects simulations positive streamers in humid air, focusing on H 2 O cross sections, photoionization models, and chemistry sets. Simulations are performed air with a mole fraction 0%, 3% or 10% using an axisymmetric fluid model. Five section sets considered, which lead to significant differences resulting electron attachment coefficient. As result, streamer velocity can vary by up about 50% O. compare results three models: Naidis model for...

We investigate discharge inception in air, uniform background electric fields above and below the breakdown threshold. perform 3D particle simulations that include a natural level of ionization form positive O$_{2}^-$ ions. When field rises detachment threshold, which are similar electrons can detach from start avalanches. These avalanches together create one large discharge, contrast to `double-headed' streamers found many fluid simulations. On other hand, breakdown, something must enhance...