Modelling of Plasma-antenna Coupling and Non-linear Radio Frequency Wave-plasma-wall Interactions in the Magnetized Plasma Device Under Ion Cyclotron Range of Frequencies PDF Download
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Author: LingFeng Lu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Ion Cyclotron Resonant Heating (ICRH) by waves in 30-80MHz range is currently used in magnetic fusion plasmas. Excited by phased arrays of current straps at the plasma periphery, these waves exist under two polarizations. The Fast Wave tunnels through the tenuous plasma edge and propagates to its center where it is absorbed. The parasitically emitted Slow Wave only exists close to the launchers. How much power can be coupled to the center with 1A current on the straps? How do the emitted radiofrequency (RF) near and far fields interact parasitically with the edge plasma via RF sheath rectification at plasma-wall interfaces? To address these two issues simultaneously, in realistic geometry over the size of ICRH antennas, this thesis upgraded and tested the Self-consistent Sheaths and Waves for ICH (SSWICH) code. SSWICH couples self-consistently RF wave propagation and Direct Current (DC) plasma biasing via non-linear RF and DC sheath boundary conditions (SBCs) at plasma/wall interfaces. Its upgrade is full wave and was implemented in two dimensions (toroidal/radial). New SBCs coupling the two polarizations were derived and implemented along shaped walls tilted with respect to the confinement magnetic field. Using this new tool in the absence of SBCs, we studied the impact of a density decaying continuously inside the antenna box and across the Lower Hybrid (LH) resonance. Up to the memory limits of our workstation, the RF fields below the LH resonance changed with the grid size. However the coupled power spectrum hardly evolved and was only weakly affected by the density inside the box. In presence of SBCs, SSWICH-FW simulations have identified the role of the fast wave on RF sheath excitation and reproduced some key experimental observations. SSWICH-FW was finally adapted to conduct the first electromagnetic and RF-sheath 2D simulations of the cylindrical magnetized plasma device ALINE.
Author: LingFeng Lu
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Ion Cyclotron Resonant Heating (ICRH) by waves in 30-80MHz range is currently used in magnetic fusion plasmas. Excited by phased arrays of current straps at the plasma periphery, these waves exist under two polarizations. The Fast Wave tunnels through the tenuous plasma edge and propagates to its center where it is absorbed. The parasitically emitted Slow Wave only exists close to the launchers. How much power can be coupled to the center with 1A current on the straps? How do the emitted radiofrequency (RF) near and far fields interact parasitically with the edge plasma via RF sheath rectification at plasma-wall interfaces? To address these two issues simultaneously, in realistic geometry over the size of ICRH antennas, this thesis upgraded and tested the Self-consistent Sheaths and Waves for ICH (SSWICH) code. SSWICH couples self-consistently RF wave propagation and Direct Current (DC) plasma biasing via non-linear RF and DC sheath boundary conditions (SBCs) at plasma/wall interfaces. Its upgrade is full wave and was implemented in two dimensions (toroidal/radial). New SBCs coupling the two polarizations were derived and implemented along shaped walls tilted with respect to the confinement magnetic field. Using this new tool in the absence of SBCs, we studied the impact of a density decaying continuously inside the antenna box and across the Lower Hybrid (LH) resonance. Up to the memory limits of our workstation, the RF fields below the LH resonance changed with the grid size. However the coupled power spectrum hardly evolved and was only weakly affected by the density inside the box. In presence of SBCs, SSWICH-FW simulations have identified the role of the fast wave on RF sheath excitation and reproduced some key experimental observations. SSWICH-FW was finally adapted to conduct the first electromagnetic and RF-sheath 2D simulations of the cylindrical magnetized plasma device ALINE.
Author: Abdolrahim Frouhar
Publisher:
ISBN:
Category : Plasma heating
Languages : en
Pages : 184
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Author: Jeffrey Rufinus
Publisher:
ISBN:
Category :
Languages : en
Pages : 208
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Category : Aeronautics
Languages : en
Pages : 704
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Author: Sergei Krasheninnikov
Publisher: Springer Nature
ISBN: 3030495949
Category : Science
Languages : en
Pages : 269
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This book reviews the current state of understanding concerning edge plasma, which bridges hot fusion plasma, with a temperature of roughly one million degrees Kelvin with plasma-facing materials, which have melting points of only a few thousand degrees Kelvin. In a fact, edge plasma is one of the keys to solution for harnessing fusion energy in magnetic fusion devices. The physics governing the processes at work in the edge plasma involves classical and anomalous transport of multispecies plasma, neutral gas dynamics, atomic physics effects, radiation transport, plasma-material interactions, and even the transport of plasma species within the plasma-facing materials. The book starts with simple physical models, then moves on to rigorous theoretical considerations and state-of-the-art simulation tools that are capable of capturing the most important features of the edge plasma phenomena. The authors compare the conclusions arising from the theoretical and computational analysis with the available experimental data. They also discuss the remaining gaps in their models and make projections for phenomena related to edge plasma in magnetic fusion reactors.
Author: Lorenzo Mazzilli
Publisher:
ISBN:
Category :
Languages : en
Pages : 150
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Author: James Oren Browning
Publisher:
ISBN:
Category :
Languages : en
Pages : 266
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Author: Robert J. Papa
Publisher:
ISBN:
Category : Plasma (Ionized gases)
Languages : en
Pages : 44
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Author: Lei Zhang
Publisher:
ISBN:
Category : Magnetic fields
Languages : en
Pages : 218
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Both space and laboratory plasmas can be associated with static magnetic field, and the field geometry varies from uniform to non-uniform. This thesis investigates the impact of magnetic geometry on wave modes in cylindrical plasmas. The cylindrical configuration is chosen so as to explore this impact in a tractable but experimentally realisable configuration. Three magnetic geometries are considered: uniform, focused and rippled. For a uniform magnetic field, wave oscillations in a plasma cylinder with axial flow and azimuthal rotation are modelled through a two-fluid flowing plasma model. The model provides a qualitatively consistent description of the plasma configuration on a Radio Frequency (RF) generated linear magnetised plasma (WOMBAT, Waves On Magnetised Beams And Turbulence [Boswell and Porteous, Appl. Phys. Lett. 50, 1130 (1987)]), and yields agreement between measured and predicted dependences of the wave oscillation frequency with axial field strength. The radial profile of the density perturbation predicted by this model is consistent with the data. Parameter scans show that the dispersion curve is sensitive to the axial field strength and the electron temperature, and the dependence of the oscillation frequency with electron temperature matches the experiment. These results consolidate earlier claims that the density and floating potential oscillations are a resistive drift mode, driven by the density gradient. This, to our knowledge, is the first detailed physics modelling of plasma flows in the diffusion region away from the RF source. For a focused magnetic field, wave propagations in a pinched plasma (MAGPIE, MAGnetised Plasma Interaction Experiment [Blackwell et al., Plasma Sources Sci. Technol. 21, 055033 (2012)]) are modelled through an ElectroMagnetic Solver (EMS) based on Maxwell's equations and a cold plasma dielectric tensor. [Chen et. al., Phys. Plasmas 13, 123507 (2006)] The solver produces axial and radial profiles of wave magnitude and phase that are consistent with measurements, for an enhancement factor of 9.5 to the electron-ion Coulomb collision frequency and a 12% reduction in the antenna radius. It is found that helicon waves have weaker attenuation away from the antenna in a focused field compared to a uniform field. This may be consistent with observations of increased ionisation efficiency and plasma production in a non-uniform field. The relationship between plasma density, static magnetic field strength and axial wavelength agrees well with a simple theory developed previously. Moreover, the wave amplitude is lowered and the power deposited into the core plasma decreases as the enhancement factor to the electron-ion Coulomb collision frequency increases, possibly due to the stronger edge heating for higher collision frequencies. For a rippled magnetic field, the spectra of radially localised helicon (RLH) waves [Breizman and Arefiev, Phys. Rev. Lett. 84, 3863 (2000)] and shear Alfvén waves (SAW) in a cold plasma cylinder are investigated. A gap-mode analysis of the RLH waves is first derived and then generalised to ion cyclotron range of frequencies for SAW. The EMS is employed to model the spectral gap and gap eigenmode. For both the RLH waves and SAW, it is demonstrated that the computed gap frequency and gap width agree well with the theoretical analysis, and a discrete eigenmode is formed inside the gap by introducing a defect to the system's periodicity. The axial wavelength of the gap eigenmode is close to twice the system's periodicity, which is consistent with Bragg's law, and the decay length agrees well with the analytical estimate. Experimental realisation of a gap eigenmode on a linear plasma device such as the LArge Plasma Device (LAPD) [Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] may be possible by introducing a symmetry-breaking defect to the system's periodicity. Such basic science studies could provide the possibility to accelerate the science of gap mode formation and mode drive in toroidal fusion plasmas, where gap modes are introduced by symmetry-breaking due to toroidicity, plasma ellipticity and higher order shaping effects. These studies suggest suppressing drift waves in a uniformly magnetised plasma by increasing the field strength, enhancing the efficiency of helicon wave production of plasma by using a focused magnetic field, and forming a gap eigenmode on a linear plasma device by introducing a local defect to the system's periodicity, which is useful for understanding the gap-mode formation and interaction with energetic particles in fusion plasmas.
Author: Janet Watkins Smith
Publisher:
ISBN:
Category :
Languages : en
Pages : 240
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