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Showing 1 to 20 of 23 for “"energy confinement"”.
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Momentum transport, radial electric field, and ion thermal energy confinement in very high temperature plasmas
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1998.
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Experimental study of turbulent heat transport in Alcator C-Mod
… work provided new information about the Ohmic confinement transition, from the linear to the saturated confinement regime with the increase in average density. It was found that Te fluctuations near the edge (r/a0~.85) tend to decrease across the Ohmic confinement transition. Although the Ohmic …
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Methods for Testing Transport Theories
… collisions theory underestimates the rates of energy losses. The main sources of energy transport are instabilities due to fluctuations in magnetic fields, electric fields, and plasma density and/or temperature gradient. Although many theoretical models have been introduced to describe …
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Characterization of a turbulence bifurcation underlying L-mode confinement transitions on Alcator C-Mod
Empirical energy confinement scalings play a crucial role in the design of tokamak fusion reactors, measuring how quickly energy is transported by turbulence from the fusion-producing core to conduction loss at the edge. Unfortunately, experiments often exhibit discontinuous changes in scaling …
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Gallium Nitride phononic crystal resonator
… here is a folded PnC structure to relax energy confinement in the non-resonant dimension and to enable routing access of piezoelectric transducers inside the resonant cavity. This provides a clean spectrum over a wide frequency range and improves series resistance relative to transmission …
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Improving particle confinement in inertial electrostatic fusion for spacecraft power and propulsion
Fusion energy is attractive for use in future spacecraft because of improved fuel energy density and reduced radioactivity compared with fission power. Unfortunately, the most promising means of generating fusion power on the ground (Tokamak based reactors like ITER and inertial confinement …
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Study of density fluctuations and particle transport at the edge of I-mode plasmas
… C-Mod has accessed the Linear ohmic confinement, Saturated ohmic confinement, L-Mode and ELM-free, ELMy and Enhanced D[alpha] H-Mode regimes. Recently, another novel regime, the IMode, has been identified[1][2][3][4]. I-modes feature the presence of steep H-Mode-like electron and ion …
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Edge transport barrier studies on the Alcator C-Mod tokamak
… tokamak plasmas accompany transitions from low confinement (L-mode) to high confinement (H-mode) and exhibit large density and temperature gradients in a narrow pedestal region near the last closed flux surface (LCFS). Because tokamak energy confinement depends strongly on the boundary condition …
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Pedestal structure and stability in high-performance plasmas on Alcator C-Mod
… the steep gradients act as a source of free energy for Edge-Localized Mode (ELM) instabilities, which on ITER- or reactor-scale devices can drive large, explosive bursts of particle and energy transport leading to unacceptable levels of heat loading and erosion damage to plasma-facing …
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Acoustic Waveguides and Sensors for High Temperature and Gamma Radiation Environment
… is designed. It achieved strong acoustic energy confinement so surface perturbations no longer affected the wave propagation. Single crystal sapphire fiber features low acoustic loss, and survivability under high temperature. It is also chosen as an acoustic waveguide. AFBGs are fabricated …
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Theoretical explanations of I-mode impurity removal and H-mode poloidal pedestal asymmetries
… fueling for optimum tokamak performance. High confinement mode operation was discovered 35 years ago to almost quadruple fusion power, and later explained by turbulence reduction by sheared flows. Less than a decade ago, improved mode operation was discovered to have the same desirable …
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Theoretical prediction of [tau]E and [beta]⁻ in a large aspect ratio LDX
… (LDX) is a novel experiment to study the confinement of a high-temperature plasma in the magnetic field of a superconducting ring of wire. The levitated magnet produces a poloidal closed-line magnetic field characteristic of an ideal point dipole or a hard core Z-pinch magnetic …
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Particle simulation of laser-produced plasmas on the basis of analytic magnetohydrodynamic solutions
Inertial confinement fusion experiments using laser beams have reported the emission of hot electrons in large quantities. This phenomenon has been one of the major hindrances to the efficient compression of a thermonuclear target. This, however, leads to the speculation of a number of non-fusion …
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Monolithically integrated MEMS resonators and oscillators in standard IC technology
… theory and adiabatic theorem. Superior energy confinement is achieved, allowing record high Q ~ 14, 800 and fo - Q ~ 4.85 x 10¹³ for CMOS-RBTs at 3 GHz. Simulation, modeling, optimization, proto- typing and testing of these resonators is presented. RBTs in FinFET technologies are also …
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Finite-beta simulations of HIT-SI and HIT-SI3 using the NIMROD code
… the central plasma will relax towards a minimum energy state while conserving helicity, which is the spheromak state. This non-axisymmetric helicity injection additionally enables the usage of Imposed Dynamo Current Drive (IDCD) to sustain the equilibrium that forms. Numerical studies have been …
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Whole-device modeling of HIDRA plasmas for experimental planning
… using 1-dimensional (radial) particle and energy diffusion equations with a Bohm diffusivity. The primary innovation made here for the core analysis is a way to solve the diffusion equations without imposing a boundary condition at the edge of the confined region. The MHD pressure …
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Technology and engineering of liquid lithium for fusion applications
… all have root causes that lie in particle and energy exchanges that occur at the plasma boundary. Solid divertors, currently made mainly out of carbon, beryllium, or tungsten, can be strongly eroded by the edge plasma and appear as impurities in the plasma, leading to higher radiative losses. …
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Characterization of main ion properties for the optimization of future fusion power plants
In the search for a clean and sustainable energy source for our society, fusion energy emerges as a promising candidate. The realization of a fusion power plant on Earth faces important technological and physical challenges. This thesis is a multidisciplinary project that addresses the optimization …
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Spectral Optimization Problems Controlling Wave Phenomena
… advancing time. The rate of spatially localized energy decay can be measured in terms of the eigenvalues of the scattering resonance problem, a non-selfadjoint eigenvalue problem consisting of the time-harmonic wave (Helmholtz) equation with outgoing radiation condition at infinity. Specifically, …
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A study on the ion temperature gradient driven turbulence in tokamak plasmas
The continuous growth of the energy worldwide consumption is one of the most important challenges to our civilization. New kinds of energy resources are without doubt needed. Nuclear fusion promises to supply large amounts of energy, with minimal environmental impact. This has motivated at least …
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