PLASIMO history

The plasma groups at the faculty of applied physics of the TU/e have a long tradition in the field of Collisional Radiative Models (CRMs). In the past these were mainly used as diagnostic tools, i.e. for the interpretation of spectroscopy. In 1990 the idea came up in the group Equilibrium and Transport in Plasmas (ETP) of Prof. Daniel C. Schram to construct a more 'complete' plasma model that would predict spectroscopic plasma quantities as well as other plasma properties, such as densities, temperatures and the electromagnetic and flow fields.

A group of students consisting of Emile de Jong (master student), Dany Benoy and Frank Fey (both PhD students) started with the construction of a 2-dimensional plasma transport code under the guidance of Joost van der Mullen. Using the computer language Pascal a model was constructed for studying the atmospheric Inductively Coupled Plasmas (ICP) in Ar: a well-known plasma source used in the field of spectrochemical analysis. Basic ingredients were the algorithm for the magnetic vector potential, the hydrodynamic equations and the module for the chemistry of a non-LTE argon plasma. Anticipating to geometrically pinched configurations the code was written in generalized ortho-curvilinear coordinates. When Emile de Jong finished his study it was possible to model not only the ICP but also the cascade arc: a DC driven plasma source. So, two different plasma sources could be modeled using modules of one and the same code. Modularity had always been a driving concept; it was the reason to choose Pascal instead of Fortran, a language that at that time was more familiar in the field of scientific computing.

In 1992 the code was rewritten by Dany Benoy in the language C and was called PLASIMO, an acronym for PLAsma SImulation MOdel. This version of the code was the basis of his thesis [Benoy1993] extended and used by Ger Jansen who got in 2000 his PhD degree on a thesis [Jansen2000] based of a design concept; the design of PLASIMO. Apart from the Ar chemistry (atomic plasma) attention was paid to the modeling of molecular plasmas; to that end the chemistry of H2 and O2 plasmas was explored. Apart from the plasma created in the cascaded arc and in a plasma expansion chamber he also worked on the microwave induced plasma (MIP) system as used by POF (Plasma Optical Fibres); a company (-division) that afterwards merged into Draka Comteq.

The plasma source studied by Jan van Dijk [Dijk2001] was the QL lamp; an induction lamp that Philips brought on the market in 1990. Ingredients of previous studies of Benoy and Janssen were used, such as the ortho-curvilinear grid generation module and the magnetic vector potential. A difference with previous studies was the chemistry. Like the tubular fluorescence lamp the plasma of the QL lamp burns on Hg in a buffer gas, mainly Ar. But most importantly was the change in language: C was replaced by C++. Moreover, the modularity aspects got much more attention. The programming style, based on an object-oriented approach, made it possible to reuse and extend existing code easily.

With the aim to make the model more user-friendly and applicable in industrial environment, a Graphical User Interface GUI was developed. This demonstrates the hierarchical structure of the model, guides the simulation, controls the calculation and allows the user to monitor the behavior of the variables involved in the plasma model. PLASIMO became much more a model construction platform than just one (single) model.

In constructing the current C++ version of PLASIMO, Jan van Dijk worked closely together with Harm van der Heijden, Bart Hargers and Kurt Garloff. Van der Heijden [Heijden2003] used the platform for the study of radiation transport in the sulfur lamp while Hartgers [Hartgers2003] was mainly devoted to time dependent modeling of the plasmas in fluorescence lamps. The C++ version was further used by Colin Johnston [Johnston2003], Bart Broks (Plasmas for laser wakefield acceleration, [Broks2006]), Mark Beks (Elemental diffusion in HID lamps, [Beks2008]) and Michiel van den Donker (MIPs, [Donker2008]).

Under guidance of Gerrit Kroesen and Frits de Hoog, Gerjan Hagelaar started in 1997 in the adjacent group EPG with the modeling of micro discharges. Based on experience with the SIGLO codes that were written in Fortran by Leanne Pitchford and Jean-Pierre Boeuf at Université Paul Sabatier in Toulouse, France, he constructed the Micro-Discharge 2-Dimensional (MD2D) code. In this work [Hagelaar], supported by the Philips Research laboratory, much attention was paid to plasma-electrode interactions. So, in contrast to PLASIMO, MD2D had to cope with space charge. It therefore had a Poisson equation solver on board. On the other hand as the closed systems of micro discharges under study are non-flowing, MD2D was not equipped with a solver to compute pressure driven flows, a Navier-Stokes solver.

In the beginning of the millennium, the Plasma project moved from the group ETP to the group Elementary Processes in Gas Discharges (EPG) of Prof. Gerrit Kroesen. There, MD2D was rewritten in C++ and equipped with the PLASIMO GUI features. This was done by Jan van Dijk, who got a Post Doc position at EPG and Wouter Brok, at that time a PhD student at EPG. One of the topics of his thesis [Brok2005] was the modeling of plasma ignition. The MD2D code has since been fully integrated in PLASIMO. Apart from fluid modeling Wouter Brok also constructed the basis for a Monte Carlo module. This MC module was used by Marc van der Velden (2008) to create a Particle In Cell Monte Carlo model to study radiation created plasmas. The C++ version of MD2D was used by Diana Mihailova for her study on sputtering hollow cathode discharges [Mihailova2010] and by Ana Sobota for a study of breakdown of HID plasma lamps [Sobota2011].

The microwave plasma modeling efforts that had started with the work of Ger Janssen were continued by Michiel van den Donker [VanDenDonker2008] and later by Manuel Jimenez-Diaz [Jimenez2011], Sara Rahimi [Rahimi2014] and Efe Kemaneci [Kemaneci2014]. In this period, plasma deposition was simulated for the first time with PLASIMO. Particularly noteworthy are the contributions of Emile Carbone [Carbone2013] to the development of detailed collisional-radiative models, in particular for argon. While the emphasis of his work was on experiments on microwave plasmas, he has been instrumental in improving PLASIMO's capabilities for handling the complex interplay between collisional and radiative kinetics in plasmas in general, and argon plasmas in particular.

Major contributions to PLASIMO's flow simulation capabilities were made by Niels Lammers [Lammers2012], who implemented two turbulence modules to PLASIMO as part of his PhD studies on laser-induced shock wave cleaning of EUV photomasks. The flow module was improved in many ways by Kim Peerenboom [Peerenboom2012] as part of her studies on the Magnum PSI plasma source, which is used to support research on wall materials for fusion applications. Other major contributions are the addition of the capabilities to handle magnetized plasmas and plasmas that do not have a dominant background gas. She implemented a novel module for the diffusive fluxes, based on the Stefan-Maxwell equations. Of special interest is her approach to the discretization of the system of equations. That has been realized in a collaboration with Jan ten Thije Boonkkamp of the Mathematics and Informatics department at TU/e. The work on the discretization of transport equations matured further thanks to the impressive study of Lei Liu in this field [Liu2013]. He was able to provide formal proofs of conjectures on the convergence properties of some of the equations of interest to plasma physics, and implemented improved discretization schemes that take into account the source and accumulation of field variables in the expressions for the fluxes of the properties of interest, also for coupled sets of transport equations.

In recent years there is a growing interest in plasmas in complex gases and gas mixtures. It is then beneficial to study the chemistry of interest in a spatially averaged or global model. Wouter Graef [Graef2012] developed such model and used that to study, among others, argon plasmas with many excited states. Jesper Janssen [Janssen2014] improved PLASIMO's capabilities to calculate transport properties in complex mixtures with great accuracy. In part of these studies he worked in close collaboration with Mykhailo Gnybida, who joined the PLASIMO team as a PostDoc for more than a year.

This work on complex plasmas is continuing until today. Tafizur Rehman is building on the work of Kemaneci and Rahimi to achieve a chemical reduction of plasmas using techniques that originate from combustion engineering. Peter Koelman and Samaneh Tadayon are engaged in a project that targets the numerical simulation of the production of Solar Fuels, mor particular on the production of methane by the reduction of carbon-dioxide and the addition of hydrogen in a microwave plasma that is powered by renewable energy sources.

Since its inception in 1990, PLASIMO has developed into one of the leading platforms for plasma simulation worldwide. It has dozens of active academic and industrial users and continues to be updated to the needs of its users. The appeal of PLASIMO to outside users has grown enormously with the establishment of the EPG-spinoff company Plasma Matters B.V. by Diana Mihailova in October 2015. This company offers licenses and consultancy services that were hard to realize by an academic research group.