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Author: Aaron Craig Bader Publisher: ISBN: Category : Languages : en Pages : 220
Book Description
In this thesis we discuss measurements and modeling of minority heated fast-ion distributions in the Ion Cyclotron Range of Frequencies (ICRF) on the Alcator C-Mod tokamak. Analysis of fast-ions >100Te is important for both ITER and a future fusion reactor as both will have a significant population of 3.5 MeV alpha particles generated in fusion reactions. Fast particles in this energy range can drive unstable modes such as Toroidal Alfvén Eigenmodes (TAEs) and Reversed Shear Alfvén Eigenmodes (RSAEs). Furthermore, energetic ions may display plasma properties that differ from the bulk plasma. It is crucial to benchmark current simulation codes with measurements from highly energetic fast-ions on current devices. This thesis will focus on measurements of the fast-ion distribution made on C-Mod with an upgraded Compact Neutral Particle Analyzer (CNPA). Measurements of the fast-ion distributions will reveal strong dependences of the fast-ion effective temperature on both electron density and plasma current. For further analysis, we use the simulated distributions generated by the coupled full-wave spectral solver AORSA, with the zero orbit-width bounce-averaged Fokker-Planck code CQL3D. A new synthetic diagnostic integrated into CQL3D is used to make direct comparisons with the CNPA. We find that for plasmas that have a steady-state fast-ion distribution (df /dt = 0) the simulation and the experiment have good agreement. However, in simulations where the fast-ion distribution is evolving in time (df/dt =/ 0) we find a discrepancy between the simulation and the experimental results. The simulation is seen to evolve much slower than the experiment. Various reasons for the discrepancy are explored, including the possibility of a violation of the quasi-linear theory used in CQL3D.
Author: Aaron Craig Bader Publisher: ISBN: Category : Languages : en Pages : 220
Book Description
In this thesis we discuss measurements and modeling of minority heated fast-ion distributions in the Ion Cyclotron Range of Frequencies (ICRF) on the Alcator C-Mod tokamak. Analysis of fast-ions >100Te is important for both ITER and a future fusion reactor as both will have a significant population of 3.5 MeV alpha particles generated in fusion reactions. Fast particles in this energy range can drive unstable modes such as Toroidal Alfvén Eigenmodes (TAEs) and Reversed Shear Alfvén Eigenmodes (RSAEs). Furthermore, energetic ions may display plasma properties that differ from the bulk plasma. It is crucial to benchmark current simulation codes with measurements from highly energetic fast-ions on current devices. This thesis will focus on measurements of the fast-ion distribution made on C-Mod with an upgraded Compact Neutral Particle Analyzer (CNPA). Measurements of the fast-ion distributions will reveal strong dependences of the fast-ion effective temperature on both electron density and plasma current. For further analysis, we use the simulated distributions generated by the coupled full-wave spectral solver AORSA, with the zero orbit-width bounce-averaged Fokker-Planck code CQL3D. A new synthetic diagnostic integrated into CQL3D is used to make direct comparisons with the CNPA. We find that for plasmas that have a steady-state fast-ion distribution (df /dt = 0) the simulation and the experiment have good agreement. However, in simulations where the fast-ion distribution is evolving in time (df/dt =/ 0) we find a discrepancy between the simulation and the experimental results. The simulation is seen to evolve much slower than the experiment. Various reasons for the discrepancy are explored, including the possibility of a violation of the quasi-linear theory used in CQL3D.
Author: Pablo Rodríguez Fernández (Ph. D.) Publisher: ISBN: Category : Languages : en Pages : 191
Book Description
Perturbative transport experiments in magnetically confined plasmas have shown, for more than 20 years, that the injection of cold pulses at the plasma edge can trigger the fast increase of core temperature. Because no single standard local transport model tried to date has been able to reproduce satisfactorily all the observed temporal behavior in the experiments, these transient transport phenomena feature prominently as an open question in the community and as a challenge for predictive capabilities in tokamak burning plasmas, such as ITER and SPARC. For the first time after more than two decades of experimental evidence, this Thesis resolves this long-standing enigma in plasma transport, by modeling of experiments conducted on the Alcator C-Mod and DIII-D tokamaks. Predictive integrated simulations with the Trapped Gyro Landau Fluid (TGLF) quasilinear transport model demonstrate that the increase of core temperature in some regimes, and lack thereof in other regimes, can be explained by a change in dominant linear micro-instability in the plasma core. The effect of major radius, electron density and plasma current on the cold pulse are well captured by TGLF, including the relative change in position of the temperature flex point as current density changes. Linear stability analysis of simulated density and current scans in Alcator C-Mod reveals a competition between trapped electron and ion temperature gradient modes as the main driver of the core transient response. Measurements of electron density evolution during the cold-pulse propagation in DIII-D are enabled by a high time resolution density profile reflectometer. The density evolution reveals the quick propagation of a pulse from edge to core, which is the mechanism to transiently increase core temperature in low-collisionality plasmas. The work presented in this Thesis demonstrates that the existence of nonlocal heat transport phenomena is not necessary for explaining the behavior and time scales of cold-pulse experiments in tokamak plasmas.
Author: National Academies of Sciences, Engineering, and Medicine Publisher: National Academies Press ISBN: 0309469333 Category : Science Languages : en Pages : 61
Book Description
In January 2003, President George W. Bush announced that the United States would begin negotiations to join the ITER project and noted that "if successful, ITER would create the first fusion device capable of producing thermal energy comparable to the output of a power plant, making commercially viable fusion power available as soon as 2050." The United States and the other ITER members are now constructing ITER with the aim to demonstrate that magnetically confined plasmas can produce more fusion power than the power needed to sustain the plasma. This is a critical step towards producing and delivering electricity from fusion energy. Since the international establishment of the ITER project, ITER's construction schedule has slipped and ITER's costs have increased significantly, leading to questions about whether the United States should continue its commitment to participate in ITER. This study will advise how to best advance the fusion energy sciences in the United States given developments in the field, the specific international investments in fusion science and technology, and the priorities for the next ten years developed by the community and the Office of Fusion Energy Sciences (FES) that were recently reported to Congress. It will address the scientific justification and needs for strengthening the foundations for realizing fusion energy given a potential choice of U.S. participation or not in the ITER project, and develops future scenarios in either case. This interim report assesses the current status of U.S. fusion research and of the importance of burning plasma research to the development of fusion energy as well as to plasma science and other science and engineering disciplines. The final report will present strategies that incorporate continued progress toward a burning plasma experiment and a focus on innovation.
Author: C Wendell Horton, Jr Publisher: World Scientific ISBN: 9814678686 Category : Science Languages : en Pages : 248
Book Description
The promise of a vast and clean source of thermal power drove physics research for over fifty years and has finally come to collimation with the international consortium led by the European Union and Japan, with an agreement from seven countries to build a definitive test of fusion power in ITER. It happened because scientists since the Manhattan project have envisioned controlled nuclear fusion in obtaining energy with no carbon dioxide emissions and no toxic nuclear waste products.This large toroidal magnetic confinement ITER machine is described from confinement process to advanced physics of plasma-wall interactions, where pulses erupt from core plasma blistering the machine walls. Emissions from the walls reduce the core temperature which must remain ten times hotter than the 15 million degree core solar temperature to maintain ITER fusion power. The huge temperature gradient from core to wall that drives intense plasma turbulence is described in detail.Also explained are the methods designed to limit the growth of small magnetic islands, the growth of edge localized plasma plumes and the solid state physics limits of the stainless steel walls of the confinement vessel from the burning plasma. Designs of the wall coatings and the special 'exhaust pipe' for spent hot plasma are provided in two chapters. And the issues associated with high-energy neutrons — about 10 times higher than in fission reactions — and how they are managed in ITER, are detailed.
Author: Paul Chappell Ennever Publisher: ISBN: Category : Languages : en Pages : 139
Book Description
Turbulence in tokamak plasmas is the primary means by which energy is transported from the core of the plasma to the edge, where it is lost, and is therefore the main limitation of tokamak plasma performance. Dilution of the main-ion species was found to have a stabilizing effect on ion gyroradius scale turbulence in tokamak plasmas. Dilution of deuterium tokamak plasmas is the reduction of the ratio of the deuterium ion density to the electron density, nD=ne, to less than 1.0 through the introduction of low-Z impurity species into the plasma. Controlled dilution experiments were performed on Alcator C-Mod wherein plasmas at a range of electron density and plasma current were seeded with nitrogen while a cryopump held the electron density fixed. The electron density fluctuations due to turbulence were monitored using a phase contrast imaging (PCI) diagnostic, an absolutely calibrated diagnostic that measures the line-integral of the electron density fluctuations along 32 vertical chords. In these experiments the seeding reduced the PCI density fluctuations, and had a stabilizing effect on the ion energy transport. The seeding also reversed the direction of intrinsic rotation in certain cases. Nonlinear simulations using the gyrokinetic turbulence code GYRO were performed using measured kinetic profiles from the dilution experiments both before and after the nitrogen seeding. The GYRO simulations reproduced the observed reduction in the turbulent ion energy transport with the nitrogen seeding. The GYRO simulated turbulent density fluctuations were compared to the PCI measurements using a synthetic diagnostic, and they were found to be consistent. GYRO simulations were also performed varying only the main ion dilution to explore the theoretical effects of the dilution on energy transport. Through this it was found that the dilution reduced the turbulent ion energy transport in a wide variety of cases, but primarily increased the critical gradient at low densities, and primarily reduced the stiffness of the transport at high densities. This dilution effect is related to observations of reductions in energy transport from seeding on other tokamaks, and will likely have an impact on ITER and future fusion reactors.
Author: Wojciech Fundamenski Publisher: Cambridge University Press ISBN: 0521851718 Category : Science Languages : en Pages : 445
Book Description
A complete and up-to-date summary of power exhaust in fusion plasmas, for academic researchers and graduate students in plasma physics.
Author: National Research Council Publisher: National Academies Press ISBN: 0309090822 Category : Science Languages : en Pages : 209
Book Description
Significant advances have been made in fusion science, and a point has been reached when we need to decide if the United States is ready to begin a burning plasma experiment. A burning plasmaâ€"in which at least 50 percent of the energy to drive the fusion reaction is generated internallyâ€"is an essential step to reach the goal of fusion power generation. The Burning Plasma Assessment Committee was formed to provide advice on this decision. The committee concluded that there is high confidence in the readiness to proceed with the burning plasma step. The International Thermonuclear Experimental Reactor (ITER), with the United States as a significant partner, was the best choice. Once a commitment to ITER is made, fulfilling it should become the highest priority of the U.S. fusion research program. A funding trajectory is required that both captures the benefits of joining ITER and retains a strong scientific focus on the long-range goals of the program. Addition of the ITER project will require that the content, scope, and level of U.S. fusion activity be defined by program balancing through a priority-setting process initiated by the Office of Fusion Energy Science.
Author: Sergei Krasheninnikov Publisher: Springer Nature ISBN: 3030495949 Category : Science Languages : en Pages : 269
Book Description
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: Aaron Craig Bader
Author: Aaron Craig Bader
Author: Pablo Rodríguez Fernández (Ph. D.)
Author: National Academies of Sciences, Engineering, and Medicine
Author: C Wendell Horton, Jr
Author: Paul Chappell Ennever
Author: 
Author: Wojciech Fundamenski
Author: National Research Council
Author: 
Author: Sergei Krasheninnikov