Time-resolved gas temperature measurements by laser absorption in a pulsed microwave hydrogen discharge

Abstract

Diode laser absorption spectroscopy is used for determination of the translation temperature of hydrogen in surface-wave-created microwave discharges in a 16 mm inner diameter quartz tube, both in pulsed and continuous modes. It is shown that the gas temperature, deduced from the Doppler profile of H α , 656.3 nm line, is almost constant along the plasma column. It increases from 1000 to 2500 K as the pressure increases from 1 to 10 Torr for microwave powers ranging from 150 to 700 W. In a steady-state discharge, the influence of pressure and power is explained by considering thermal diffusion and power balance via an analytical calculation. Over a wide range of power and pressure, the gas temperature is proportional to the injected power density. In time-resolved temperature measurements with pulsed discharges, the characteristic time for the gas heating and the establishment of the steady-state is found to be of the order of 80 µs.

Activation energy of an asymmetrical, radio frequency discharge with methane

“…Results supporting this assumption were obtained by Meichsner et al and Riccardi et al [28,29]. Moreover, the situation is similar to surfacewave-produced microwave and positive-column discharges [27,30]. Hence, the expansion of the active plasma zone is approximated by a linearly falling curve starting at the point of maximum intensity thus that the net intensity, i.e., the integral below the measured curve, is maintained (Fig.…”

Time resolved optical emission spectroscopy in power modulated atmospheric pressure plasma jet

“…Moreover, studying the plasma kinetics in modulated and pulsed discharges offer the possibility to understand the mechanisms and processes involved from a fundamental point of view. Plentiful articles have already been published on plasma kinetics of active species in plasma, using time resolved measurements [9][10][11][12][13].…”

Rayleigh scattering on a microwave surfatron plasma to obtain axial profiles of the atom density and temperature

“…Generally they can be divided as based on emission spectroscopy [12], laser absorption spectroscopy [12][13][14][15] and laser scattering [16]. In case of emission spectroscopy the T a can for instance be obtained from the rotational temperature of excited molecular species.…”