Responses of a long-coil pulse-modulated induction plasma

Abstract

Abstract-Radio-frequency inductively coupled plasma in a pulse modulated approach was generated by a MOSFET inverter supply of high electric efficiency. The plasma torch has an extremely long coil region of 153 mm, which is an attractive feature for advanced materials processing, especially for better and more efficient vaporizing of solids. The operating conditions were: argon flow of 80 or 90 L/m at atmospheric pressure; supply power of 30 kW; and pulse on-time of 10 ms at 67% duty factor. Spectroscopic measurements were carried out to determine the temporal plasma properties, including the effects of shimmer current level (SCL) upon the spectral intensities. Additionally, a time-dependent two-dimensional numerical model was solved for the same operating conditions employed in the experiment to predict and compare the plasma properties. Pulsed plasma dissipation sustained for a minimum SCL of 43% for 80 L/m gas flow-rate, and at any level below 43%, the plasma disappeared. Temporal variation of argon line intensities at 751 and 763.5 nm is similar, though the upper level intensity of the former one was significantly stronger than the latter. Intensified change of intensity is found at lower SCL because of higher change in the coil current and, in turn, in the plasma power. The predicted intensity of the 751-nm argon line showed similar behavior to the experimental intensity though the response around the instant of on-pulsation is somewhat slower.

Transient Behavior of Current Modulated 2-T Inductively Coupled Plasma

“…Specifically, the instantaneous large-jump of electron temperature with the on-transition will help to reduce or eradicate the discrepancy observed when a LTE model is used (for instance, in the results of [25]- [28]). Only a kinetic nonequilibrium model may sufficiently explain the correct plasma field properties in a transient thermal plasma.…”

“…A number of articles have been published recently on the transient behavior of an RF-ICP assuming LTE [22]- [29]. The time-dependent LTE model has been found to fail in explaining plasma behavior in some instants of a pulse modulated RF-ICP, as reported by Paul et al [25]- [27] and Hossain et al [28]. The discrepancy seen between the experimental and LTE-based theoretical results for an RF-ICP has been explained as due to the nonequilibrium condition within a transient plasma.…”

A comparative study of transient characteristics of argon and hydrogenated-argon pulse-modulated induction thermal plasma

“…The model considers coil current pulsation instead of power to have similarity with the experiment and it is based on our last publication [14]. This model solves the time-dependent conservation equations along with the vector potential form of Maxwell's equations, as listed in the Appendix, using the SIMPLER algorithm of Patankar [15].…”

“…The algorithm is based on the control volume scheme for solving the transport equations of incompressible fluids. The reasonable assumptions and boundary conditions are the same as those described in [14]. …”

Stable operation region and dynamic behavior of Ar pulse‐modulated induction thermal plasma with different molecular gases

“…In this context, the authors proposed to deliberately sustain the dynamic (transient) state of a thermal plasma by pulse amplitude modulation of a coil current that supports ICTP at a period of several milliseconds [10][11][12][13][14][15][16][17]. Such a thermal plasma is referred to as a pulse-modulated induction thermal plasma (PMITP).…”