Diagnosis of large volume pulse modulated Ar-H/sub 2/ plasmas

Abstract

Summary form only given. Atmospheric pressure plasma in pre-mixed Ar/H/sub 2/ (Ar: 84% molar concentration) flow was generated experimentally at pulse-modulated approach. The plasma torch has a special kind of feature; the length of coil region is extremely large, 158 mm. Ratio of the coil length to coil diameter is about 3:2, which is usually opposite in the ordinary torch. This huge coil length should have caused high plasma region and thus, should be more suitable for materials processing. Pulse modulation of plasma helps to understand the changes of plasma responses with time, and thus, this technique is likely to be helpful to control the plasma energy and species concentration in time domain for better application of radio-frequency (RF) inductively coupled plasma (ICP). The numerical model (Mostaghimi et al., 1998), which used 2-dimensional field variations and was for optically thin and local thermodynamic equilibrium (LTE) considerations, revealed many characteristic properties of plasma for sudden change in active power of plasma. The model was found effective to predict different response times of plasma. Experimentally generated pulse-modulated plasma (Sakuta et al., 1999) reported on-time and pressure effects upon the atomic argon line intensity at 751 nm wavelength. Both works were for same torch configuration. Our present work is to reveal spectroscopically measured results of the new ICP torch with large coil length. In addition, the ICP code of Mostaghimi et al. was changed for current pulsation and used in predicting ICP responses for the same operating conditions of experiment.