A global model of a radiofrequency (rf) inductively coupled H 2 plasma discharge in the Deuterium Negative Ion Source Experiment (DENISE) has been developed using the numerical code 'Global Model Solver' (GMS). The volume-averaged energy and particle balance equations, along with the quasi-neutrality condition, are numerically solved to determine the averaged densities of all the species included in the model and the electron temperature. The effects of the multicusp magnetic field and of the asymmetry of the source chamber are considered in the model. The values of the volume-averaged electron density and the average electron temperature obtained are compared to experimental measurements in the pressure and input power ranges of interest and a reasonably good agreement is found.
The ion dynamics in the high-voltage sheath of a capacitively coupled radio-frequency plasma has been investigated using mass-resolved ion energy analysis in combination with a two-dimensional particle-in-cell (PIC) code. A symmetric confined discharge is designed allowing highly accurate comparisons of measured ion energy distribution functions in high-voltage sheaths with simulation results. Under the conditions investigated, the sheaths are not only collisional, but also chemically complex. This situation is common in applications but rare in laboratory experiments. Excellent agreement has been found for a hydrogen discharge benchmarking the code. Hydrogen is of particular interest since its light mass gives detailed insight into sheath dynamics, and an extensive database of collisional cross sections is available. The H3+ ion was found to be the dominant ion in the sheaths and the plasma bulk under most conditions investigated. H3+ exhibits the typical saddle-shaped ion energy distribution function indicative of ions created in the plasma bulk and traversing the entire sheath potential. H+ and H2+ are predominantly formed through collisions in the high-voltage sheath. H2+ ion energy distribution functions show structures resulting from symmetric charge exchange collisions with the background gas. Minor discrepancies between the experimental results and PIC simulations indicate slightly lower plasma densities in the simulation, resulting in larger sheath width.
A study of the gas-phase kinetics and the plasma chemistry for an rf inductively coupled H 2 plasma discharge, in the deuterium negative ion source experiment (DENISE), has been carried out by means of a global model of the discharge implemented by the numerical code, Global Model Solver (GMS), which gives results for the spatially averaged densities of the species included in the model and the electron temperature in the steady state. The modelling of the discharge includes H − , with the production mechanism assumed to be dissociative attachment of H 2 (v). The effect of the magnetic filter in the source is taken into account for obtaining an estimate of the H − density also in the extraction chamber. The differences in the cross-section data assumed for some processes, between this paper and previous work, are pointed out, along with the consequences on H − density. The ratio between the H − density and the electron density obtained with GMS for the considered negative ion production mechanism is always far lower than 0.1, even with the most optimistic assumptions for H − production that can be put forward.
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