## Global Modeling of a Non-Maxwellian Discharge in COMSOL®

##### Jose Gregorio November 19, 2018

Global modeling of plasmas is a powerful approach to study large chemistry sets. In these models, the reactions are represented by rate coefficients. In particular, the rate coefficients of electron impact collisions depend on the electron energy distribution function (EEDF), which is often non-Mawellian and can be computed from an approximation of the Boltzmann equation (BE). Here, we explain how to create a global model fully coupled with the BE in the two-term approximation using the COMSOL Multiphysics® software.

Lire la Suite##### Annette Pahl July 5, 2017

Plasma modeling normally requires knowing the electron energy distribution function (EEDF) as well as transport properties like electron mobility and diffusivity. To accurately calculate these quantities with the Boltzmann equation, we must also know the electron density (and possibly the density of all species subject to electron impact reactions). However, the electron (and species densities) are outputs of a plasma model, resulting in a catch-22. Let’s take a look at how to overcome this challenge using an example app.

Lire la Suite##### Bridget Cunningham April 24, 2017

Due to the complex pumping scheme of high-power CO2 lasers, there are many species and collisions to consider in their analysis. This makes modeling plasma behavior in these devices — a key element in their optimization — a challenging task. Applying a multilevel approach, one researcher used the COMSOL Multiphysics® software to create a full 3D model of planar discharge in a CO2 laser. The results showcase the homogeneity of the discharge while offering further potential for optimizing laser designs.

Lire la Suite##### Bridget Paulus October 17, 2016

Developing a device that generates nuclear fusion would provide a nearly limitless amount of clean energy on Earth. But while work on thermonuclear fusion began in the 1950s, engineers are still trying to make this goal a reality. One approach has been to use magnetic confinement devices known as tokamaks. See why a group of engineers at MIT’s Plasma Science Fusion Center (PSFC) turned to simulation to address a key challenge in tokamak design: instability due to plasma disruptions.

Lire la Suite##### Walter Frei February 25, 2016

If you’ve ever worked with the Terminal boundary condition in COMSOL Multiphysics, you know that this electrical boundary condition can apply a current or voltage, among other options. But did you know that you can also dynamically switch between excitation types during a transient simulation? This is useful if you are trying to model a current- or voltage-limited power supply, for example. Today, we will look at how to implement such a switching behavior.

Lire la Suite##### Annette Pahl April 8, 2015

In a previous blog post, we introduced readers to different kinds of electron energy distribution functions (EEDFs) and their importance in plasma modeling. Today, we focus our attention on the Boltzmann Equation, Two-Term Approximation interface, demonstrating its use with an example from our Model Library.

Lire la Suite##### Annette Pahl February 10, 2015

Plasmas can exhibit a large variety of properties. There are plasmas with high and low ionization degrees, as well as those with high and low pressures and hot and cold temperatures. Different equations and modeling approaches are necessary for each kind of plasma. This blog post gives an overview of the different plasma types and shows when to use which of the interfaces available in the Plasma Module.

Lire la Suite##### Annette Pahl October 22, 2014

When modeling plasmas, various options exist for choosing an ion temperature. Your choice, however, may strongly influence your model’s results. Let’s discuss the theoretical reason behind this phenomenon and study an example involving an inductively coupled plasma (ICP) to illustrate the influence the different ion temperature options have on your model’s results.

Lire la Suite##### Annette Pahl August 4, 2014

The electron energy distribution function (EEDF) plays an important role in plasma modeling. Various approaches can be used to describe the EEDF, such as Maxwellian, Druyvesteyn, or using a solution of the Boltzmann equation. Today, we will demonstrate the influence the EEDF has on a plasma model’s results. Additionally, we present a way to compute the EEDF with the Boltzmann Equation, Two-Term Approximation interface.

Lire la Suite##### Daniel Smith December 11, 2013

Microwave plasmas, or wave-heated discharges, find applications in many industrial areas such as semiconductor processing, surface treatment, and the abatement of hazardous gases. This blog post describes the theoretical basis of the Microwave Plasma interface available in the Plasma Module.

Lire la Suite##### Phil Kinnane April 26, 2012

We’ve just got another finished article and layout back for COMSOL News and it looks as great as the others, but for different reasons. We usually ask a couple of our partners to write an article for COMSOL News to provide users with some more technical background to modeling. AltaSim Technologies, who are certified consultants and even run courses in COMSOL, have written an article about surface plasmon resonance.

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