Characteristics of High-Power Helium Microwave-Induced Plasma at Atmospheric Pressure for Fine-Particle Analysis

Helium microwave-induced plasma (He-MIP) for fine-particle analysis was generated using 2.45 GHz microwave power (similar to 1 kW) with an Okamoto cavity of the surface wave mode at atmospheric pressure. The iron excitation temperature and the electron density of the plasma were measured. With an input microwave power of 800 W, an excitation temperature of the high energy part of 8000 K, and an electron density of 2 X 10(14)/cm(3) were obtained. The sample particles in an Al plate ablated by a Q-switched Nd : YAG laser (266 nm, 30 mW, 10 Hz, 3 similar to 5 ns) or nebulization of suspension of Al(2)O(3) powder (mean dia. 1 mu m) was introduced into the center of an annular He-MIP through an inner tube of a torch along with the carrier gas (He or Ar). The time-resolved atomic emission spectrometry (AFS) was Studied for a particulate composition analysis of the laser ablation and the nebulization of suspension. Preliminary experimental data were obtained. The He-MIP AES could be detected with sufficient sensitivity.