The goal of this thesis is to design a setup which can be used as a prototype for the TECH reactor. The TECH reactor is a cylinder with rounded edges, in which a microwave plasma will be formed....Show moreThe goal of this thesis is to design a setup which can be used as a prototype for the TECH reactor. The TECH reactor is a cylinder with rounded edges, in which a microwave plasma will be formed. The cavity should resonate with the right eigenmode at a constant frequency of 2.45 GHz, and the excitation structure should produce a reflection coefficient of smaller than 0.8, enabling a tuning device to maximize power transfer. These conditions must hold for a broad range of conductivities of the plasma. Firstly, the effect of a resonance frequency tuning ring inside the cavity was researched, in order to keep the right eigenmode at a constant frequency of 2.45 GHz. Secondly, the excitation structure was optimized to ensure that at the relevant plasma conductivities, the reflections from the setup were minimized. Later simulations yielded that for almost all conductivities of the plasma, the setup was sufficiently impedance matched to the waveguide to enable an auto tuning device to prevent reflections. Thirdly, unexpected eigenmodes of the cavity were discovered. Therefore, adjustments were made to the cavity such that the resonance frequencies of other modes would not be close to 2.45 GHz, to prevent the excitation of these modes. This thesis continued the work of De Man [3]. In the end, the simulations yielded promising results and the setup is almost fully designed. Soon, experiments with the electric field in the cavity can be carried out, which form an important step towards being able to measure plasma breakdown.Show less
This paper addresses the optimization of RF power absorption into a Laser- Induced plasma, naturally consisting of some highly conductive plasma torus and a surrounding cloud of less conductive...Show moreThis paper addresses the optimization of RF power absorption into a Laser- Induced plasma, naturally consisting of some highly conductive plasma torus and a surrounding cloud of less conductive plasma. By reproducing experimentally determined values in simulations, a characterization of the two plasma-components is made. Using CCD-images, the dimensions of the plasma-components are determined, and an Ansatz is made for the electron density distribution and decay of the conductive component. Using 2.45 GHz power reflection- and 57 GHz voltage transmission measurement data, the dielectric properties of both plasma-components are determined by parametric sweeps in COMSOLTM. Finally, the most accurate characterization of the LI-plasma is implemented in simulations on magnetic induction heating within a TE-102 rectangular and a TE-011 cylindrical cavity, and the resulting power absorption ratios are compared to that of capacitive heating in a TE-101 rectangular cavity.Show less
This research poses the first steps towards confining a laser-produced helium plasma torus in an active swirling ring vortex flow. By comparison of one-dimensional Navier-Stokes simulations of a...Show moreThis research poses the first steps towards confining a laser-produced helium plasma torus in an active swirling ring vortex flow. By comparison of one-dimensional Navier-Stokes simulations of a Gaussian energy deposition in atmospheric helium with extracted shock front positions from schlieren measurements, we developed a full three-dimensional initial condition for the gas state profiles in the early stages of the plasma evolution. High mach number flow simulations of this initial condition showed strong similarities with plasma torus evolution measurements. By varying the focusing length of the laser pulse we showed that the symmetry in the energy deposition plays a crucial role in the evolution of the plasma torus. Extending on the initial condition construction, we modelled an asymmetric energy deposition which we showed has qualitative agreements with measurements for the torus formation. Power transmission measurements showed that at a full laser pulse energy of 275 mJ approximately 50% is absorbed, of which 22% is shown to go into thermodynamic energy forming the strong shock wave. Finally, we used plasma measurements of an asymmetric energy deposition to design a flow nozzle using a turbulent flow model to confine the plasma torus in a swirling vortex flow.Show less
Experimentally it has been found that a high power laser pulse focussed on a Helium gas at atmospheric pressure creates a plasma that over time assumes a torus shape. This process could see...Show moreExperimentally it has been found that a high power laser pulse focussed on a Helium gas at atmospheric pressure creates a plasma that over time assumes a torus shape. This process could see applications in plasma chemistry and is a first step towards a self-confined magnetohydrodynamics plasma. However, the torus shape is eventually destroyed as cold gas flow from the center of the torus splits the plasma. To study this process the gas dynamics shortly after the laser pulse are reduced to one dimension by applying cylindrical symmetry. The resulting equations are solved numerically. By fitting the one dimensional simulation results to experimental data, a three dimensional starting condition is proposed. Using this starting condition, a three dimensional axi-symmetric simulation is performed which is capable of reproducing both torus formation and splitting. These simulations show that the primary process responsible for torus formation is a low pressure area that is dragged behind the strong shock fronts moving perpendicular to the laser axis. Arguments for the local thermodynamic equilibrium of the plasma are presented. This justifies the application of the Saha equation to find the electron density from the simulated pressures and temperatures. Finally, passive modifications of the plasma environment are considered to prevent the plasma from splitting and provide flow confinement of the plasma for up to 100 μs.Show less
Recently it was observed that laser-induced breakdown creates macroscopic rings of plasma. These rings are of interest because they can be used to construct inherently stable magnetized plasma...Show moreRecently it was observed that laser-induced breakdown creates macroscopic rings of plasma. These rings are of interest because they can be used to construct inherently stable magnetized plasma structures. The goal is to form a better understanding of the processes within and properties of these plasma rings. We study the different stages in the time-evolution of the plasma using an intensified CCD with nanosecond resolution exposure time. Furthermore, the spectrum of the emitted light is studied and through Boltzmann analysis the temperature is derived.Show less
In this thesis we will investigate the Hopf map, a differentiable map from the three-sphere to the two-sphere. Its fibres, the inverse images of points on the sphere, are circles that are all...Show moreIn this thesis we will investigate the Hopf map, a differentiable map from the three-sphere to the two-sphere. Its fibres, the inverse images of points on the sphere, are circles that are all linked with every other fibre. Based on the Hopf map we will construct divergenceless vector fields that have a physical interpretation as the magnetic field in the theory of magnetohydrodynamics. The concept of linking relates to helicity in this theory, a quantity that will be used to exhibit self-stable configurations of plasma.Show less
