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Final Technical Report: Global Field Aligned Mesh and Gyrokinetic Field Solver in a Tokamak Edge Geometry

Description: This project was a collaboration between researchers at the California Institute of Technology and the University of California, Irvine to investigate the utility of a global field-aligned mesh and gyrokinetic field solver for simulations of the tokamak plasma edge region. Mesh generation software from UC Irvine was tested with specific tokamak edge magnetic geometry scenarios and the quality of the meshes and the solutions to the gyrokinetic Poisson equation were evaluated.
Date: May 15, 2013
Creator: Cummings, Julian C.
Partner: UNT Libraries Government Documents Department

Center for Momentum Transport and Flow Organization in Plasmas and Magnetofluids (CMTFO)

Description: The CMTFO funding partially supports a junior researcher and a graduate student at UCI. During this project, we have further developed the global gyrokinetic particle code GTC to study the momentum transport in tokamak driven by electrostatic ion temperature gradient (ITG) turbulence [1] with kinetic electrons and by collisionless trapped electron mode (CTEM) turbulence [2]. We have also upgraded GTC for fully electromagnetic simulation and for linear plasma configuration with verification and validation of the electron temperature gradient (ETG) turbulence in Columbia Linear Machine. The followings are the highlights on the physics results reported in the key publications of this project.
Date: February 28, 2014
Creator: Lin, Zhihong
Partner: UNT Libraries Government Documents Department

SciDAC Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas

Description: During the first year of the SciDAC gyrokinetic particle simulation (GPS) project, the GPS team (Zhihong Lin, Liu Chen, Yasutaro Nishimura, and Igor Holod) at the University of California, Irvine (UCI) studied the tokamak electron transport driven by electron temperature gradient (ETG) turbulence, and by trapped electron mode (TEM) turbulence and ion temperature gradient (ITG) turbulence with kinetic electron effects, extended our studies of ITG turbulence spreading to core-edge coupling. We have developed and optimized an elliptic solver using finite element method (FEM), which enables the implementation of advanced kinetic electron models (split-weight scheme and hybrid model) in the SciDAC GPS production code GTC. The GTC code has been ported and optimized on both scalar and vector parallel computer architectures, and is being transformed into objected-oriented style to facilitate collaborative code development. During this period, the UCI team members presented 11 invited talks at major national and international conferences, published 22 papers in peer-reviewed journals and 10 papers in conference proceedings. The UCI hosted the annual SciDAC Workshop on Plasma Turbulence sponsored by the GPS Center, 2005-2007. The workshop was attended by about fifties US and foreign researchers and financially sponsored several gradual students from MIT, Princeton University, Germany, Switzerland, and Finland. A new SciDAC postdoc, Igor Holod, has arrived at UCI to initiate global particle simulation of magnetohydrodynamics turbulence driven by energetic particle modes. The PI, Z. Lin, has been promoted to the Associate Professor with tenure at UCI.
Date: December 18, 2013
Creator: Lin, Zhihong
Partner: UNT Libraries Government Documents Department

Implementations of mesh refinement schemes for particle-in-cell plasma simulations

Description: Plasma simulations are often rendered challenging by the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation region, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the mesh refinement technique. We briefly discuss the challenges posed by coupling this technique with plasma Particle-In-Cell simulations and present two implementations in more detail, with examples.
Date: October 20, 2003
Creator: Vay, J.-L.; Colella, P.; Friedman, A.; Grote, D.P.; McCorquodale, P. & Serafini, D.B.
Partner: UNT Libraries Government Documents Department

Novel Methods in the Particle-In-Cell Accelerator Code-Framework Warp

Description: The Particle-In-Cell (PIC) Code-Framework Warp is being developed by the Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) to guide the development of accelerators that can deliver beams suitable for high energy density experiments and implosion of inertial fusion capsules. It is also applied in various areas outside the Heavy Ion Fusion program to the study and design of existing and next-generation high-energy accelerators, including the study of electron cloud effects and laser wakefield acceleration for example. This paper presents an overview of Warp’s capabilities, summarizing recent original numerical methods that were developed by the HIFS-VNL (including Particle-In-Cell with Adaptive Mesh Refinement, a large-timestep “drift-Lorentz” mover for arbitrarily magnetized species, a relativistic Lorentz invariant leapfrog particle pusher, simulations in Lorentz boosted frames, an electromagnetic solver with tunable numerical dispersion and efficient stride20 based digital filtering), with great emphasis on the description of the mesh refinement capability. Selected examples of applications of the methods to the abovementioned fields are given.
Date: September 1, 2011
Creator: Vay, J.-L.; Grote, D. P.; Cohen, R. H.; Friedman, A.; Grote, D. P.; Cohen, R. H. et al.
Partner: UNT Libraries Government Documents Department

Dynamics of a plasma discharge in a mirror field

Description: A cool plasma discharge in mirror geometry is modeled with ions flowing along field lines into electrodes beyond the throats. The velocity of the flow is determined by the electrode sheath prcpenties and nozzle-like phenomena in the mirror and ion source. This model is applicable to the wet-wood burner'' reactor and mirror target schemes. (auth)
Date: January 24, 1974
Creator: Lee, E. P. & McNamara, B.
Partner: UNT Libraries Government Documents Department

Numerical simulations of plasmas with smoothing in phase space and filtering in time. Progress report, October 1, 1972--September 30, 1973

Description: The research is directed tcward the development of new numerical methods for plasma simulation and their application to physical problems of current interest to Controlled Thermonuclear Research. During the past year, research on the project has been concerned with the following problems- (1) analysis of numerical effects in particle simulation of whistler wave propagation, (2) theoretical and numerical studies of triggered emissions from electrons correlated in phase by a large-amplitude whistler wave, (3) development of long- time-step algorithms, and (4) anomalous absorption of radiation in weakly' collisional plasmas. (auth)
Date: January 1, 1973
Creator: Denavit, J.
Partner: UNT Libraries Government Documents Department

Application of adaptive mesh refinement to particle-in-cell simulations of plasmas and beams

Description: Plasma simulations are often rendered challenging by the disparity of scales in time and in space which must be resolved. When these disparities are in distinctive zones of the simulation domain, a method which has proven to be effective in other areas (e.g. fluid dynamics simulations) is the mesh refinement technique. We briefly discuss the challenges posed by coupling this technique with plasma Particle-In-Cell simulations, and present examples of application in Heavy Ion Fusion and related fields which illustrate the effectiveness of the approach. We also report on the status of a collaboration under way at Lawrence Berkeley National Laboratory between the Applied Numerical Algorithms Group (ANAG) and the Heavy Ion Fusion group to upgrade ANAG's mesh refinement library Chombo to include the tools needed by Particle-In-Cell simulation codes.
Date: November 4, 2003
Creator: Vay, J.-L.; Colella, P.; Kwan, J.W.; McCorquodale, P.; Serafini, D.B.; Friedman, A. et al.
Partner: UNT Libraries Government Documents Department

Portable implementation of implicit methods for the UEDGE and BOUT codes on parallel computers

Description: A description is given of the parallelization algorithms and results for two codes used ex- tensively to model edge-plasmas in magnetic fusion energy devices. The codes are UEDGE, which calculates two-dimensional plasma and neutral gas profiles, and BOUT, which cal- culates three-dimensional plasma turbulence using experimental or UEDGE profiles. Both codes describe the plasma behavior using fluid equations. A domain decomposition model is used for parallelization by dividing the global spatial simulation region into a set of domains. This approach allows the used of two recently developed LLNL Newton-Krylov numerical solvers, PVODE and KINSOL. Results show an order of magnitude speed up in execution time for the plasma equations with UEDGE. A problem which is identified for UEDGE is the solution of the fluid gas equations on a highly anisotropic mesh. The speed up of BOUT is closer to two orders of magnitude, especially if one includes the initial improvement from switching to the fully implicit Newton-Krylov solver. The turbulent transport coefficients obtained from BOUT guide the use of anomalous transport models within UEDGE, with the eventual goal of a self-consistent coupling.
Date: February 17, 1999
Creator: Rognlien, T D & Xu, X Q
Partner: UNT Libraries Government Documents Department

Recent progress in linear and nonlinear studies of toroidal Alfven eigenmode

Description: TAE modes are studied in linear and nonlinear regimes using several kinetic/MHD hybrid models. It is shown that the stability of TAE mode is largely determined by its radial mode structure. The calculated stability thresholds are correlated well with observations, including the recently observed alpha-driven TAE modes in the TFTR DT experiments. In the nonlinear regime, quasilinear simulations with multiple modes show that the saturation level is enhanced by nonlinear wave-particle resonance overlapping when the linear growth rate exceeds a critical value. A fully self-consistent {delta}f noise reduction method for the 3D particle/MHD hybrid model is developed.
Date: May 1, 1997
Creator: Fu, G.Y.; Chen, Y. & Budny, R.
Partner: UNT Libraries Government Documents Department

Collisionless damping of perpendicular magnetosonic waves in a two-ion-species plasma

Description: Propagation of finite-amplitude magnetosonic waves in a collisionless plasma containing two ion species is studied with a one-dimensional, fully electromagnetic code based on a three-fluid model. It is found that perpendicular magnetosonic waves are damped in a two-ion-species plasma; a magnetosonic pulse accelerates heavy ions in the direction parallel to the wave front, which results in the excitation of a longer wavelength perturbation behind the pulse. The damping due to the energy transfer from the original pulse to the longer wavelength perturbation occurs even if the plasma is collisionless and the pulse amplitude is small. The theoretically obtained damping rate is in agreement with the simulation result.
Date: August 1, 1996
Creator: Dogen, Daiju; Toida, Mieko & Ohsawa, Yukiharu
Partner: UNT Libraries Government Documents Department

Control of plasma poloidal shape and position in the DIII-D tokamak

Description: Historically, tokamak control design has been a combination of theory driving an initial control design and empirical tuning of controllers to achieve satisfactory performance. This approach was in line with the focus of past experiments on simply obtaining sufficient control to study many of the basic physics issues of plasma behavior. However, in recent years existing experimental devices have required increasingly accurate control. New tokamaks such as ITER or the eventual fusion power plant must achieve and confine burning fusion plasmas, placing unprecedented demands on regulation of plasma shape and position, heat flux, and burn characteristics. Control designs for such tokamaks must also function well during initial device operation with minimal empirical optimization required. All of these design requirements imply a heavy reliance on plasma modeling and simulation. Thus, plasma control design has begun to use increasingly modern and sophisticated control design methods. This paper describes some of the history of plasma control for the DIII-D tokamak as well as the recent effort to implement modern controllers. This effort improves the control so that one may obtain better physics experiments and simultaneously develop the technology for designing controllers for next-generation tokamaks.
Date: November 1, 1997
Creator: Walker, M.L.; Humphreys, D.A. & Ferron, J.R.
Partner: UNT Libraries Government Documents Department

Nonlinear theory of kinetic instabilities near threshold

Description: A new nonlinear equation has been derived and solved for the evolution of an unstable collective mode in a kinetic system close to the threshold of linear instability. The resonant particle response produces the dominant nonlinearity, which can be calculated iteratively in the near-threshold regime as long as the mode doe snot trap resonant particles. With sources and classical relaxation processes included, the theory describes both soft nonlinear regimes, where the mode saturation level is proportional to an increment above threshold, and explosive nonlinear regimes, where the mode grows to a level that is independent of the closeness to threshold. The explosive solutions exhibit mode frequency shifting. For modes that exist in the absence of energetic particles, the frequency shift is both upward and downward. For modes that require energetic particles for their existence, there is a preferred direction of the frequency shift. The frequency shift continues even after the mode traps resonant particles.
Date: May 1, 1997
Creator: Berk, H.L.; Pekker, M.S. & Breizman, B.N.
Partner: UNT Libraries Government Documents Department

3D simulation studies of tokamak plasmas using MHD and extended-MHD models

Description: The M3D (Multi-level 3D) tokamak simulation project aims at the simulation of tokamak plasmas using a multi-level tokamak code package. Several current applications using MHD and Extended-MHD models are presented; high-{beta} disruption studies in reversed shear plasmas using the MHD level MH3D code, {omega}{sub *i} stabilization and nonlinear island saturation of TAE mode using the hybrid particle/MHD level MH3D-K code, and unstructured mesh MH3D{sup ++} code studies. In particular, three internal mode disruption mechanisms are identified from simulation results which agree which agree well with experimental data.
Date: December 31, 1996
Creator: Park, W.; Chang, Z.; Fredrickson, E. & Fu, G.Y.
Partner: UNT Libraries Government Documents Department

Effect of divertor geometry on plasma detachment in DIII-D

Description: This paper explores the physics of the recently installed Radiative Divertor Plasma divertor (RDP) in DIII-D through the use of UEDGE simulation with experimentally derived plasma parameters. The RDP is a nearly closed baffle and cryopumping system in the upper divertor of DIII-D. [l] One measure of the effectiveness of the RDP is the achievement of a detached plasma with a lower core density than in the open divertor (present in the lower divertor in DIII-D). Plasma detachment, observed on all diverted tokamaks, is a change in the plasma state which results in a decrease in both the ion current and heat load on the divertor plate. These reductions together with the related drop in electron temperature are important for divertor design in high power devices such as ITER, in which detached operation is assumed [2]. Both UEDGE modeling and DIII-D experiments show a reduction of 25% to 50% in the core density necessary for plasma detachment in the RDP compared to the open divertor.
Date: May 19, 1998
Creator: Wolf, N. S., Dickinson College, LLNL
Partner: UNT Libraries Government Documents Department

Collisionless electron heating in inductively coupled discharges

Description: A kinetic theory of collisionless electron heating is developed for inductively coupled discharges with a finite height L. The novel effect associated with the finite-length system is the resonance between the bounce motion of the electrons and the wave frequency, leading to enhanced heating. The theory is in agreement with results of particle simulations.
Date: July 1, 1996
Creator: Shaing, K.C. & Aydemir, A.Y.
Partner: UNT Libraries Government Documents Department