Exotische Plasma's: goed voor je gezondheid!

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Plasma Physics experiments

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Arcs: gravitational effects and pinching

Arcs are thermal plasmas: the temperatures of eletrons, ions and neutrals are roughly equal. In many cases, arcs are self-constricted. Two cases will be discussed: magnetically pinched arcs in Xe or Sn vapour (applied in EUV radiation sourcces) and AC arcs in metal halide vapours (used for lamps). In the first case, the pinching is essential for driving up the multiple ionisation to the required levels. For these arcs, we will look into sub-nanosecond phenomena. In the second case, the pinching is influenced by gravity. We will present measurements and simulations for gravity levels between 0 and 10 g

A Monte Carlo modelling study of the electrons in the microdischarges in plasma addressed liquid crystal displays

Fluid models for gas discharges are based on restrictive assumptions for the electron-energy distribution function (EEDF). In this work we investigate the validity and consequences of these assumptions for discharges occurring in plasma addressed liquid crystal (PALC) displays. For this purpose we have developed a Monte Carlo model for electrons, which we compare to a fluid model. A direct current (DC) discharge and afterglow in the PALC geometry are considered, with helium as a discharge gas. In the discharge, the EEDF calculated with the Monte Carlo model displays several non-equilibrium phenomena, such as peaks of fast electrons that have undergone none or only a few collisions, and the absence of a high-energy tail. Although these features are not incorporated in the fluid model, both models lead to virtually the same electron density profile. However, the ionization rate obtained with the Monte Carlo model is spread out over a larger region than the ionization rate in the fluid model. The Monte Carlo calculations reveal that the electrons in the afterglow have a highly non-equilibrium nature, and require a special treatment in the fluid model

On the temperature dependence of the deposition rate of amorphous, hydrogenated carbon films

The temperature behavior of the deposition rate of amorphous, hydrogenated carbon films is analyzed both experimentally and theoretically. A reactor based on the supersonic expansion of an arc plasma is used. The film thickness is measured using in situ He–Ne ellipsometry. The surface temperature is measured with thermocouples. Comparison of the presented model with the experimental results suggests that the deposited atoms and radicals diffuse over the surface in a weakly bound, adsorbed layer before they are incorporated in the film. Direct incorporation upon chemisorption is improbable

Zwaar stof

Stofdeeltjes zijn zeer ongewenst in industriële plasma’s, zoals toegepast in de halfgeleider- en zonnecelindustrie, maar ook in nucleaire fusiereactoren. Echter, voor het verwerven van fundamentele kennis, zoals bijvoorbeeld het bepalen van elektrische velden in plasma’s, zijn deze deeltjes met een afmeting van slechts enkele micrometers uitermate geschikt. Door deze microdeeltjes op te sluiten in een plasma en ze bloot te stellen aan grote versnellingen in een centrifuge, kunnen bovengenoemde elektrische velden, die van groot belang zijn voor veel plasmatoepassingen, nauwkeurig worden gemeten

On the energy influx to the substrate during sputter deposition of thin aluminium films

The integral energy influx during sputtering of thin aluminium films onto silicon wafers as well as onto small micro-disperse iron powder particles has been determined to be in the order of 0.02-0.2 J/cm2 s depending on the discharge power (10-100 W) and the target-to-substrate distance (15-4 cm). The thermal power at the substrate consists mainly of the kinetic energy of charge carriers and sputtered particles, and the released condensation heat. The contribution due to film condensation is determined by the deposition rate and the specific heat of condensation. The rather small contribution of the electrons was measured by SEERS and Langmuir-probes, whereas the influence of the ions as well as of the sputtered particles on the energy balance was studied by energy-resolved mass spectrometry. The measured integral energy influx which has been determined from the increase of the substrate temperature at the sputtering process is in good accordance with the sum of the various contributions calculated by simple model assumptions. The observed differences in the microstructure between Al-films deposited on large silicon wafers and those films deposited on small iron powder particles can be explained by differences in the thermal balance due to the energy fluxes during the plasma process

The final frontiers of cavity ring down spectroscopy : the mid-infrared

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