Topic/Type: 1. Plasma Simulation, Oral

Fluid modelling of low pressure plasma sources

G. J. M. Hagelaar

Universit? de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d' Energie), Toulouse, France

Low pressure plasma sources, where the mean free paths of the particles are comparable to the plasma dimensions, are most often simulated by kinetic models (such as particle-in-cell models) because fluid models lead to complications in both physical validity and numerical implementation. However, even rather simplistic fluid models can be extremely useful to get insight in the main physical principles of low pressure plasma sources and obtain quick estimates of their behaviour. In this presentation, we discuss the use of fluid equations for the example of an inductively coupled plasma source at a pressure below 0.3 Pa.

Radio-frequency inductively-coupled plasmas are used in a new type of negative ion source for neutral beam injection, currently under development for the ITER fusion experiment. [1] To accompany the experimental development, a comprehensive numerical model is being developed, describing the main physical principles of this source self-consistently: inductive coupling and electron heating, magnetised plasma transport in the source body, negative ion extraction across a magnetic filter, low-density neutral flow and depletion by the plasma, chemistry of negative ion creation in the volume and at the surface, etc. The present version of this model uses fluid equations for the electron transport. We discuss the description of the electron heating due to the inductive coupling with the driving current. In particular, we propose a simple method to describe the anomalous skin effect through a fluid equation for electron momentum including a viscosity term with an effective viscosity coefficient. [2] We also discuss the effects of static and radio-frequency magnetic fields on the inductive coupling and the consequences for the plasma transport.

This work is supported by ANR (National Research Agency) under contract BLANC08-2_310122, by the ITER Federation, and by the French Atomic Energy Commission (CEA).

[1] E. Speth et al 2006 Overview of the RF source development programme at IPP Garching, Nucl. Fusion 46 S220-38

[2] G. J. M. Hagelaar 2008 Effective viscosity approach for non-local electron kinetics in inductively coupled plasmas, Phys. Rev. Lett. 100, 02001