The 'high-pressure' atmospheric (TIG) arc plasma is studied by means of a multi-Langmuir probe system. In order to determine the appropriate regime of operation, definitions of the plasma parameters for the description of the argon arc are considered and evaluations are presented. A description of the probe basic techniques is followed by an in-depth discussion of the different regimes of probe operation. The emphasis is put on atmospheric and flowing (arc) regimes. Probe sheath theories are compared and "Nonidealities" like cooling due to plasma-probe motion and probe emission mechanisms are then described.The extensive literature review reveals that the existing probe theories are inappropriate for a use in the TIG arc, because of 'high' pressure (atmospheric), broad range of ionization across the arc, flowing conditions, and ultimately, to the uncertainty about onset of Local Thermodynamical Equilibrium. The Langmuir probe system is built to operate in floating and biased conditions. The present work represents the first extensive investigation of electrostatic probes in arcs where the experimental difficulties and the primary observed quantities are presented in great detail. Analysis methodologies are introduced and experimental results are presented towards a unified picture of the resulting arc structure by comparison with data from emission spectroscopy. Results from different measurements are presented and comparison is made with data on TIG arcs present in literature. Probe obtained temperatures are lower than the values obtained from emission spectroscopy and this 'cooling' is attributed to electron-ion recombination. However, it is believed that probes can access temperatures regions not attainable by emission spectroscopy. Only axial electric potential and electric field are obtained because of the equipotential-probe requirement. Estimations of the sheath voltage and extension are obtained and a qualitative picture of the ion and electron current densities within the arc is given.on floating and plasma potentials and estimates of the sheath voltage are made, which are then compared with the results of Chapter 4. Chapter 13 deals with further 'electrical' parameters (current densities, electric field and electrical conductivity). In Chapter 14 several experimental results are presented together in order to gain a unified picture of the resulting arc structure and some observations about possible conduction structures within arcs are made. Finally Chapter 15, after a summary of the whole work, reports the conclusions obtained and suggests further investigations.

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Hyperon production in the threshold region was studied in the reaction pp → K + Λp using the time-of-flight spectrometer COSY-TOF. Exclusive data, covering the full phase-space, were taken at the three different beam momenta of p beam = 2.95, 3.20 and 3.30 GeV/c, corresponding to excess energies of ε = 204, 285 and 316 MeV, respectively. Total cross-sections were deduced for the three beam momenta to be 23.9 ± 0.8 ± 2.0 µb, 28.4 ± 1.3 ± 2.2 µb and 35.0 ± 1.3 ± 3.0 µb. Differential observables including Dalitz plots were obtained. The analysis of the Dalitz plots reveals a strong influence of the

Results on reactive atom plasma etching performed on ULE® (Corning Ultra Low Expansion) glass samples at atmospheric pressure are presented for the first time. A reactive atomic plasma technology (RAPT®), has been developed by RAPT Industries and employed for the finishing of optical surfaces. An atmospheric pressure argon inductively coupled plasma (ICP) excites a reactive gas injected through its centre. The plume of hot neutral excited species reacts at the substrate yielding controlled and repeatable trenches. In the case of ULE a material removal (up to 0.55 mm3/s) is obtained without pre‐heating the samples. Among the factors influencing the results, an increase in gas concentration at the same power does not change the sample temperature, indicating that thermo‐chemical effects do not influence the removal rates. Due to the plasma constructive constrains, increasing the gas concentration is more practical and of wider effect than increasing the power. The benefits of the process are illustrated and the extension of the technology to large optical surfaces discussed.