van der Hwp Harm Heijden

A self-consistent LTE model of a microwave-driven, high-pressure sulfur lamp

A one-dimensional LTE model of a microwave-driven sulfur lamp is presented to aid our understanding of the discharge. The energy balance of the lamp is determined by Ohmic input on one hand and transport due to conductive heat transfer and molecular radiation on the other. We discuss the origin of operational trends in the spectrum, present the model and discuss how the material properties of the plasma are determined. Not only are temperature profiles and electric field strengths simulated but also the spectrum of the lamp from 300 to 900 nm under various conditions of input power and lamp filling pressure. We show that simulated spectra demonstrate observed trends and that radiated power increases linearly with input power as is also found from experiment.

Quantitative two-photon laser-induced fluorescence measurements of atomic hydrogen densities, temperatures, and velocities in an expanding thermal plasma

We report on quantitative, spatially resolved density, temperature, and velocity measurements on ground-state atomic hydrogen in an expanding thermal Ar–H plasma using two-photon excitation laser-induced fluorescence (LIF). The method’s diagnostic value for application in this plasma is assessed by identifying and evaluating the possibly disturbing factors on the interpretation of the LIF signal in terms of density, temperature, and velocity. In order to obtain quantitative density numbers, the LIF setup is calibrated for H measurements using two different methods. A commonly applied calibration method, in which the LIF signal from a, by titration, known amount of H generated by a flow-tube reactor is used as a reference, is compared to a rather new calibration method, in which the H density in the plasma jet is derived from a measurement of the two-photon LIF signal generated from krypton at a well-known pressure, using a known Kr to H detection sensitivity ratio. The two methods yield nearly the same re...