Topic/Type: 1.5 Low-temperature, dusty and nano-plasmas, Poster

Dipolar microwave plasma sources: plasma modelling and operational efficiency

K. Makasheva1, 2, 3, G. Hagelaar1, 2, L. Garrigues1, 2, J.P. Boeuf1, 2

1 Universit? de Toulouse; UPS, INPT; LAPLACE (Laboratoire Plasma et Conversion d'Energie), Toulouse, France
2 CNRS; LAPLACE; Toulouse, France
3 Electronic mail : kremena.makasheva@laplace.univ-tlse.fr

Generation and maintenance of large volume, high density homogeneous plasmas, for various applications, have stimulated the development of novel plasma sources. One of the successful concepts reported in the literature [1, 2] is the multi-dipolar microwave plasma sustained by electron cyclotron resonance (ECR). It consists of a network of elementary microwave sources distributed on the plasma reactor walls. The principle of energy distribution applies for the plasma maintenance in such a configuration. The microwave plasma created by multi-dipolar sources is characterized by a high density (up to 1017 m-3), very good degree of plasma homogeneity and increased opportunity for scaling up the plasma dimensions.
This work presents a numerical study of plasma sustained by two generations of the multi-dipolar sources: the elementary source presented in [1], called here A-source and the recently designed microwave source, called Boreal, or B-source. The numerical model that we have developed is a 2D model based on fluid description. The full set of equations and physical approximations as well as the numerical methods applied to solve the plasma and the field equations are described elsewhere [3]. The plasma is sustained in argon under typical for the ECR regime gas pressures, p = 1 ? 10 Pa.
The two sources presented here have complex geometries, so that the ECR plane is not nearly flat like in conventional ECR reactors, but rather peanut-shaped for the A-source and doughnut?shaped for B-source. This slight at first sight discrepancy leads to non-negligible differences in the performance and the operational efficiency of the two sources. For example, the maximum electron density (nemax = 1.0 ? 1017m-3) achieved in the plasma sustained by the B-source is more than twice higher than the electron density in A-source plasma (nemax = 0.4 ? 1017m-3) for the same amount of the total absorbed power P = 10 W at gas pressure p = 1 Pa. The qualitative agreement with experimental results is excellent. Further results concerning plasma parameters and wave characteristics as well the main mechanisms responsible for the multi-dipolar microwave plasma will be presented.

This work is supported by the Agence Nationale de la Recherche under contract ANR06-BLAN-0177.

[1] A. Lacoste, T. Lagarde, S. B?chu, Y. Arnal and J. Pelletier 2002 Multi-dipolar plasmas for uniform processing : physics, design and performance, Plasma Sources Sci. Technol. 11, 407.

[2] A. Lacoste, S. B?chu, O. Maulat, J. Pelletier and Y. Arnal 2009 Extraction of large-area low-energy electron beams from a multi-dipolar plasma, Plasma Sources Sci. Technol. 18, 015017.

[3] G. J. M. Hagelaar, K. Makasheva, L. Garrigues and J.-P. Boeuf 2009 Modelling of a dipolar microwave plasma sustained by electron cyclotron resonance, J. Phys. D: Appl. Phys. 42, in press.