Download or read book Scaling and Transport Analysis of Divertor Conditions on the Alcator C Mod Tokamak written by Brian LaBombard and published by . This book was released on 1994 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Local Transport Analysis for the Alcator C Mod Tokamak written by Jeffrey M. Schachter and published by . This book was released on 1997 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impurity Transport in the Divertor of the Alcator C Mod Tokamak written by G. M. McCracken and published by . This book was released on 1994 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling of Boundary Transport and Divertor Target Heat Flux Implications for Advanced Divertor Concepts written by Sean Bozkurt Ballinger and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tokamaks are currently being designed and built to achieve net positive unharnessed fusion energy, an important milestone on the path to electricity production. Experimental trends predict an additional challenge in these upcoming devices: a decrease in the area of the metal wall on which the plasma deposits significant heat flux, increasing the likelihood of melting damage. The heat deposition area is proportional to a parameter called the heat flux width, which decreases with increasing poloidal magnetic field and average plasma pressure. In devices designed to achieve physics breakeven such as ITER and SPARC, the heat flux width is predicted by some estimates to be less than 1 millimeter. It is therefore crucial to develop methods to more accurately predict the heat flux width and to mitigate large heat fluxes. Data from the Alcator C-Mod tokamak are particularly relevant in the effort to predict conditions in SPARC, as both are designed to use a higher magnetic field than other major tokamak experiments. Before this work, the relationship between the heat flux width and edge profiles of plasma density and temperature in C-Mod was unknown. Studies with plasma edge simulation codes were limited to a small number of discharges at a time, with many model settings being ad-hoc and difficult to evaluate for general applicability. Simulations of C-Mod had a much shorter outer divertor leg compared to SPARC, making it difficult to use detachment studies in C-Mod to speculate on detachment in SPARC. Finally, there was only a rough idea of edge plasma conditions in SPARC, and it was not known whether detachment would even be feasible. This thesis uses data from Alcator C-Mod and simulations with the UEDGE code to investigate heat flux width scalings, detachment, and advanced divertor concepts to inform the design of next-generation tokamaks that can pro duce significant fusion energy while remaining safe against heat flux damage. This thesis begins by augmenting a C-Mod heat flux width database (containing ~300 discharges) with midplane density and temperature profile data. Detailed analysis finds that the outer target heat flux width depends on the edge plasma pressure, but fails to find a clear dependence on edge gradients. The scaling of the heat flux width with the edge pressure varies by confinement mode and is used to confirm predictions of the heat flux width of 0.2-0.4 mm in SPARC and 0.4-0.6 mm in ITER H-mode scenarios. The UEDGE code is then used to simulate the edge of Alcator C-Mod plasmas. 75 discharges from the heat flux width database are successfully modeled in UEDGE using a fully automated process that matches experimental midplane density and temperature profiles. The resulting heat flux width in UEDGE is then compared to experimental measurements, and it is found that the UEDGE and experimental values are correlated but that UEDGE overestimates the heat flux width by an average factor of 1.8. The UEDGE-modeled discharges are modified to include single-particle drift effects and (separately) to remove flux limits. These changes do not significantly improve the UEDGE heat flux width match to experiment but demonstrate the capability of this framework to evaluate which settings in the UEDGE model improve agreement with experiment over the large range of edge plasma conditions included in the C-Mod database. One particular C-Mod attached H-mode discharge is then simulated in UEDGE, and a good match is achieved to experimental data at the midplane and outer target simultaneously with full drift effects included in the model. This discharge is also simulated with a ~2x longer outer divertor leg, an important component of advanced divertor concepts that could enable better high heat flux handling. Detachment is found to occur when a nitrogen impurity is introduced at a fixed fraction of 3.5% of the main ion density in the real C-Mod geometry, while with the longer leg, detachment occurs at a significantly lower fraction of 2.4% nitrogen. This bodes well for the SPARC design, which features a long outer leg. Finally, a full-power SPARC H-mode scenario is directly simulated with UEDGE. It is found that detachment is possible at the high heat fluxes and small heat flux width predicted for SPARC and that the heat flux at the targets can remain significantly reduced with a carbon impurity fraction around 1%. This value is not a prediction of the detachment threshold in SPARC due to the use of bifurcated attached and detached solutions obtained at low power, but is encouraging when compared to the detachment thresholds in C-Mod UEDGE simulations. This study confirms that detachment is a promising solution to mitigate high heat fluxes in the SPARC full-power scenario.

Download or read book Understanding of Neutral Gas Transport in the Alcator C Mod Tokamak Divertor written by D. P. Stotler and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Understanding of Neutral Gas Transport in the Alcator C Mod Tokamak Divertor written by D. P. Stotler and published by . This book was released on 2002 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Neutral Particle Dynamics in the Alcator C Mod Tokamak written by Artur Pawel Niemczewski and published by . This book was released on 1995 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Impurity Ion Densities and Energies in the Divertor and Edge Regions of Alcator C Mod Tokamak Lab for Plasma Research Univ of Maryland College Park written by and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study to investigate impurity production and transport in the divertor and edge regions of the Alcator C-Mod tokamak through spectroscopic techniques is described. A 0.75-meter Czerny-Turner spectrometer with a 1200-g/mm grating and a 35-meter quartz optic bundle transmission line were tested. A high-resolution 2-meter spectrometer will be ordered. Data acquisition considerations are being addressed. (RWR).

Download or read book Particle Transport on the Alcator C Mod Tokamak written by Cindy R. Christensen and published by . This book was released on 1999 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book INIS Atomindex written by and published by . This book was released on 1996 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissipative Divertor Operation in the Alcator C Mod Tokamak written by B. Lipschultz and published by . This book was released on 1994 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Validation of Turbulent Transport Models on Alcator C Mod and ASDEX Upgrade written by Alexander James Creely and published by . This book was released on 2019 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis developed hardware and analysis techniques to measure two validation constraints experimentally, and then applied these constraints in the validation of plasma turbulent transport models on two tokamaks, Alcator C-Mod and ASDEX Upgrade, resulting in both greater physics understanding of multi-scale turbulent interactions and greater confidence in predictions for future fusion devices. On the path toward the clean, sustainable, and safe energy of a fusion power plant, experiment and modeling each contribute something unique. Before one can in good faith use plasma turbulent transport models to explain turbulent dynamics or predict machine performance, however, one must ensure that these models can correctly reproduce experimentally measured conditions on existing devices. Validation, the process of determining how accurately a model represents reality, has thus become a key endeavor in fusion energy research. First, this thesis developed an analysis technique to measure the electron perturbative thermal diffusivity based on tracking the propagation of heat pulses generated by partial sawtooth crashes. In addition, correlation electron cyclotron emission (CECE) hardware was constructed on both Alcator C-Mod and ASDEX Upgrade, and analysis techniques were derived, in order to measure turbulent electron temperature fluctuations. These validation constraints were applied to two turbulent transport models, the nonlinear gyrokinetic model and the quasi-linear gyrofluid model. In particular, these constraints were used to study the importance of multi-scale turbulent effects (due to coupling between ion- and electron-scales) in correctly modeling plasma behavior. The gyrokinetic codes GYRO and GENE were validated on Alcator C-Mod and ASDEX Upgrade respectively, using both constraints developed in this thesis as well as ion and electron heat fluxes from power balance, revealing that in some cases ionscale simulations are sufficient to match experimental constraints, while in other cases multi-scale effects are important. To investigate this discrepancy, a novel type of validation study was performed with the gyrofluid code TGLF, including many discharges from both machines. This study resulted in two physical criteria that determine when multi-scale effects are important, and when ion-scale simulations are sufficient to model the plasma behavior, shedding light on the physical phenomena that govern the importance of multi-scale turbulent effects.

Download or read book Turbulence and Transport Studies with Phase Contrast Imaging in the Alcator C Mod Tokamak and Comparisons with Gyrokinetic Simulations written by Liang Lin (Ph. D.) and published by . This book was released on 2009 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: (cont.) Our study shows that although the short wavelength turbulence in the ETG range is unstable in the linear ohmic regime, the nonlinear simulation with k[theta][rho]s up to 4 does not raise the electron thermal diffusivity to the experimental level, where k[theta] is the poloidal wavenumber and [rho]s is the ion-sound Larmor radius. The H-Mode studies focus on plasmas before and during internal transport barrier formation in an enhanced D[alpha], H-Mode plasma. The simulated fluctuations from GYRO agree with experimental measurements in the ITG regime. GYRO also shows good agreement in transport predictions with experimental measurements after reducing the ion temperature gradient (~15%) and adding ExB shear suppression, all within the experimental uncertainty.

Download or read book Measurement of Impurity Ion Densities and Energies in the Divertor and Edge Regions of Alcator C Mod Tokamak Progress Report February 1 1992 July 31 1992 written by and published by . This book was released on 1992 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study to investigate impurity production and transport in the divertor and edge regions of the Alcator C-Mod tokamak through spectroscopic techniques is described. A 0.75-meter Czerny-Turner spectrometer with a 1200-g/mm grating and a 35-meter quartz optic bundle transmission line were tested. A high-resolution 2-meter spectrometer will be ordered. Data acquisition considerations are being addressed. (RWR).

Download or read book High field Compact Divertor Tokamak Research on Alcator C Mod written by Ian H. Hutchinson and published by . This book was released on 1996 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of Triggering Mechanism of Internal Transport Barriers on the Alcator C Mod Tokamak Using Thomson Scattering Diagnostic written by Kirill Zhurovich and published by . This book was released on 2007 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internal transport barriers (ITBs) in tokamak plasmas are characterized by the reduction of transport in one or more of the particle, momentum, or energy channels in the core plasma region. On Alcator C-Mod, significant contributions to ITB studies were made possible with the core Thomson scattering (TS) diagnostic, which measures profiles of electron temperature (0.03