Gm Ger Janssen

A combined Thomson-Rayleigh scattering diagnostic using an intensified photodiode array

A combined Thomson–Rayleigh scattering device is discussed. It consists of a Nd:YAG laser as a light source in combination with a multichannel detection technique consisting of a gated light amplifier in combination with an optical multichannel analyzer. Special attention is focused on the analysis of the measured spectra. Including convolution methods and taking into account weak coherent effects increases the dynamic range and the accuracy of the measured electron density ne and temperature Te and neutral particle density n0. Accuracies of 1%–4% for ne, 2%–6% for Te, and 10%–50% for n0 depending on the plasma condition are obtained. The dynamic range for ne is 7×1017–1021 m−3, for n0 is 1020–1023 m−3 and for Te is 1000–50 000 K.

PLASIMO, a general model: I. Applied to an argon cascaded arc plasma

A non-LTE argon cascaded arc plasma is studied and modelled with the general plasma simulation program PLASIMO. The structure of PLASIMO is flexible and transparent, so that apart from the study given in the present paper several other multicomponent stationary plasmas in a wide pressure range ( to 1 bar), from local thermal equilibrium (LTE) to non-LTE, and with different energy coupling mechanisms can be simulated as well. The modular structure is divided into three main parts: the transport part which forms the heart of the model, the plasma configuration part, and the composition part. The latter two parts define the input parameters for the transport part and are controlled by the PLASIMO user. The three parts are again divided into separate modules. The strong modularity makes PLASIMO easy to handle and easy to adjust or expand. Results of PLASIMO applied on the cascaded arc are compared with experimental data and show reasonable agreement. The influence of the boundary conditions on the simulation results is discussed.

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.

Ionization efficiency in a geometrically pinched cascaded arc

Remote deposition allows separate optimization of the plasma production source and of the deposition process. To improve the ionization performance of the source, an argon cascaded arc plasma is studied by simulations. Improvements of the source performance in ion yield are achieved by constricting the bore of the arc channel near the entrance. Such a geometrical pinch construction leads to a higher neutral density at the arc inlet which results in increased ionization in the cascaded arc. The improved ionization performance is analysed by solving numerically the conservation laws of mass, momentum and energy in a two-dimensional hydrodynamic approximation using a pressure linked algorithm. The results are compared with those of a simplified one-dimensional formulation in order to identify the main mechanisms. The results indicate that, by constricting the bore of the arc channel, a very high ionization degree can be obtained.

Implementation of a friction-based self-consistent multicomponent diffusion model in Plasimo

In order to improve the realism of our Plasimo computer model [1, 2] in modelling multi-ion mixtures, we developed and implemented a self-consistent multicomponent diffusion model based on frictions. As presented, this diffusion model includes effects of the ambipolar electric field as well as any external electric fields. Moreover, it is comparatively easy to include other diffusion contributions. This model was shown to produce good and consistent results for both single and multi-ion mixtures.