STEEP PLASMA GRADIENTS STUDIED WITH SPATIALLY-RESOLVED THOMSON SCATTERING MEASUREMENTS

Citation
J. Jonkers et al., STEEP PLASMA GRADIENTS STUDIED WITH SPATIALLY-RESOLVED THOMSON SCATTERING MEASUREMENTS, Plasma sources science & technology, 6(4), 1997, pp. 533-539
Citations number
23
ISSN journal
09630252
Volume
6
Issue
4
Year of publication
1997
Pages
533 - 539
Database
ISI
SICI code
0963-0252(1997)6:4<533:SPGSWS>2.0.ZU;2-Z
Abstract
Plasmas created by the microwave torch Torche a Injection Axiale (TIA) , which are around 2 mm in diameter and 15 mm long, are investigated. In these plasmas large gradients are present so that the edge is suppo sed to play an important role. Using global Thomson scattering measure ments, in which global refers to the fact that the size of the laser b eam is approximately equal to the diameter of the plasma, the electron densities and temperatures were determined. However, these results le ad to discrepancies in the particle balance: the production of free el ectrons is much larger than the classical losses due to recombination, convection and diffusion. Radially resolved Thomson scattering measur ements show the plasma has a hollow structure. Although this enhances the losses due to diffusion, still a large discrepancy remains between production and destruction of free electrons in the argon plasmas. Pr obably some molecular processes are significant as well. A good candid ate is the charge transfer between argon ions and nitrogen molecules, since mixing with the surrounding air has a large impact on the plasma .