In 2012, plasma figuring was proven to be an alternative solution for the fabrication of large scale ultra-precise optical surfaces. Indeed, plasma figuring was successfully demonstrated on a metre class glass surface. The process was exceptionally rapid but residual errors were observed. This thesis addresses this issue by proposing an enhanced tool that provides a highly collimated plasma jet. The enhanced tool is characterized by a targeted material removal footprint in the range 1 to 5 mm FWHM. The energy beam is provided by an Inductively Coupled Plasma (ICP) torch equipped with a De-Laval nozzle. This thesis focuses on characterization and optimisation of the bespoke plasma torch and its plasma jet. Two research investigations were carried out using both numerical and experimental approaches. A novel CFD model was created to analyse and understand the behaviour of high temperature gas in the De-Laval nozzle. The numerical approach, that was based on appropriate profiles of temperature and velocity applied to the nozzle inlet, led to a significant reduction of computational resources. This model enabled to investigate the aerodynamic phenomena observed from the nozzle inlet up to the processed surface. Design rules and the effect of changing nozzle parameters were identified. Sensitivity analysis highlighted that the throat diameter is the most critical parameter. A challenging power dissipation analysis of the plasma torch was carried out. Temperature and flow rate in key components of the torch were measured. Experimental results enabled to calculate the power dissipation values for RF power up to 800 W and for the entire series of designed nozzles. This work enabled to scientifically understand the power dissipation mechanism in the bespoke ICP torches. In addition, by comparing the intensity of the power dissipation values, one nozzle was clearly identified as being more capable to provide a highly efficient plasma jet.

Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is now a well established analytical technique used to sample solid materials and determine their elemental composition. Two areas that are becoming increasingly important, and for which LA-ICP-MS is a key tool, are bio-imaging and the analysis of micro-particulates. However, current instrumental designs limit the practicality of the technique for these applications. This study investigates the development of a high speed, high efficiency LA-ICP-MS interface through modelling of the flow dynamics of a newly designed laser ablation cell and experimental investigation of single laser pulse response. Through this work the Sniffer-Dual Concentric Injector interface was realised. This interface reduced particle residence times within the laser cell and transport tubing. The interface was also used to investigate turbulence related aerosol dispersion within the ICP and potential designs to overcome this. The resulting design yields an interface with improved sensitivity and reduced aerosol dispersion such that a lower limit of detection is achieved, important when considering the mass of analyte in a single cell or micro-particulate, compared to existing designs. Thus the interface can be used to improve image spatial resolution as the ablation spot size, and thus pixel information, can be reduced; and also reduces total analysis time. The calibration technique Laser Ablation of a Sample In Liquid (LASIL) was also investigated as a means of calibration for solid samples. The investigation lead to the development of LASIL in a droplet, a technique that can be used to calibrate solid samples when a matrix matched standard is unavailable. The mechanism of the technique resulted in an improved laser-energy sample coupling efficiency and a reduction in the liquid to ablated mass ratio, thus decreasing sampling time. As the technique captures the ablated particulate in solution, post chemistry techniques can be used to remove analyte interferences.

La mise en œuvre de missions spatiales demande à développer de nombreuses technologies clés afin de surmonter certaines étapes cruciales. L’une d’entre elle concerne la rentrée atmosphérique : lorsque le véhicule pénètre dans la couche d’atmosphère, sa vitesse relative très grande par rapport au sol va engendrer des frottements importants ainsi qu’une augmentation de pression. L’énergie cinétique de l’objet va donc être transformée en énergie thermique et chauffer le gaz en formant une onde de choc. Les températures dépendent de la vitesse initiale, de la composition de l’atmosphère et de sa pression. Le gaz ainsi chauffé va s’ioniser et devenir un plasma, il va donc transférer sa chaleur au corps de la sonde non seulement par convection mais aussi par rayonnement. Afin de se protéger, le véhicule dispose d’un bouclier thermique pouvant résister aux phénomènes extrêmes rencontrés lors de la descente. Les contraintes supplémentaires vont imposer une géométrie particulière et un lourd bouclier. Ainsi l’objectif est d’avoir les protections les plus légères et efficaces possibles afin de permettre à la sonde de maximiser son emport en équipement scientifique. Pour cela, un des paramètres clés est de connaître le comportement et le rayonnement du plasma produit lors de la rentrée dans l’atmosphère. Cette thèse se positionne dans ce domaine d’étude: les expériences montées et réalisées ont pour objectif d’observer par moyens spectroscopiques un plasma correspondant à celui rencontré par les sondes spatiales. / Many key technologies, to overcome some crucial steps, are needed for space missions. One of them concerns the re-entry: when the vehicle enters the atmosphere layer, its high velocity relative to the ground will generate significant friction and an increase in pressure. The kinetic energy of the object will be converted into heat energy and heat the gas forming a shock wave. Temperatures depend on the initial velocity, the atmosphere composition and its pressure. The gas is ionized and become plasma, it will therefore transfer its heat to the body of the probe not only by convection but also by radiation. To protect itself, the vehicle has a heat shield that can withstand extreme phenomena encountered during the descent. Additional constraints will impose a particular geometry and a heavy shield. So the goal is to have the lightest possible and effective protections to allow the probe to maximize its payload. For this, one of the key parameters is to know the behavior of the plasma and radiation produced during re-entry into the atmosphere. This thesis is positioned in this area of ​​study: experiments to create a re-entry plasma are intended to be observed by a spectrometer.