Dependence on the scattering angle of the electron temperature and electron density in Thomson-scattering measurements on an atmospheric-pressure plasma jet

Electron temperature and electron density measurements were made in an atmo spheric-pressure argon plasma jet by line-shape analysis of Thomson-scatter ed laser light. The dependence of electron temperature and electron density on the scattering angle was investigated. Measurements were made using inc ident laser wavelengths of 532 and 355 nm. At 532 nm, the electron-ion coll ision frequency exceeds the Landau damping rate for shallow scattering angl es, and the electron plasma wave resonance structure in thr Thomson line sh ape is broadened. This resulted in dramatic increase in the apparent electr on temperature as a function of decreasing scattering angle. At 355 nm, col lisions do not affect the Thomson line shape. In this case, an angular depe ndence of the measured electron temperature is not expected and was not obs erved. Data taken at 532 nm at larger scattering angles are consistent with the 355-nm results, and show that the electrons are not in thermodynamic e quilibrium with the heavy particles.