Influence of differences in current GOSAT XCO2 retrievals on surface flux estimation
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Takagi, H↗
Engineering topics
Parker, R
Publications and source records attributed to Parker, R.
Fast-ions on Alcator C-Mod: Comparisons between Simulation and Experiment for Equilibrium and Evolving Distributions
Analysis of fast-ion distributions >100 T{sub e} is important for both ITER and a fusion reactor, as both will have a significant population of fusion-born alpha particles. Furthermore, energetic ions may display transport properties that differ from the bulk plasma. It is imperative to benchmark current simulation codes with measurements of highly energetic fast-ions on current devices. Experimental measurements of ICRF heated H-minority plasmas on Alcator C-Mod are performed with an upgraded Compact Neutral Particle Analyzer (CNPA). The CNPA consists of vertically-viewing photodiode detectors with viewing chords from r/a = {approx}0.18 to 0.6 and energies from 150 keV to 1.5 MeV. The CNPA measurements are compared to the output of a synthetic diagnostic that has been added to the Fokker-Planck solver CQL3D. CQL3D is coupled with the full-wave solver AORSA to evolve a self-consistent fast-ion distribution. Good agreement is obtained between simulation and experiment for fast ion distributions that are in steady-state (df/dt = 0). However, there are discrepancies between the experimental and simulated results for the time-dependent evolution of the fast-ion distribution. A possible explanation of the discrepancy is due to violation of certain assumptions of quasi-linear theory.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Full wave effects on the lower hybrid wave spectrum and driven current profile in tokamak plasmas
A numerical modeling of current profile modification by lower hybrid current drive (LHCD) using a fullwave/Fokker-Planck simulation code is presented. A MHD stable LHCD discharge on Alcator C-Mod was analyzed, and the current profile from full wave simulations was found to show better agreement with the experiment than a ray-tracing code. Comparison of full wave and ray-tracing simulation shows that, although ray-tracing can reproduce the stochastic wave spectrum broadening, the full wave calculation predicts even wider spectrum broadening, and the wave spectrum fills all of the kinematically allowed domain. This is the first demonstration of LHCD current profile modeling using a full wave simulation code in a multi-pass absorption regime, showing the clear impact of full wave effects on the LHCD driven current profile.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
Plasma wave simulation based on a versatile finite element method solver
The possibility of plasma wave simulation based on the finite element method (FEM) was explored, and a new full wave simulation code of the lower hybrid (LH) wave, Lower Hybrid wavE Analysis based on FEM (LHEAF), was developed. The efficient iterative solver for the LH wave [O. Meneghini, S. Shiraiwa, and R. Parker, Phys. Plasmas 16, 090701 (2009)] was coupled to one-dimensional Fokker-Planck calculation to obtain the self-consistent distribution function. In LHEAF, seamless handling of the core, scrape off layer, and antenna regions were realized and the wave launching structure were naturally included into the simulation. Simulation results of a Maxwellian tokamak plasma showed good agreement with ray tracing calculations and the TORIC-LH spectral solver [J. C. Wright, P. T. Bonoli, A. E. Schmidt et al., Phys. Plasmas 16, 072502 (2009)]. Compared to spectral domain solvers, the computational requirements are reduced significantly, allowing an Alcator C [M. Porkolab, J. J. Schuss, B. Lloyd et al., Phys. Rev. Lett. 53, 450 (1984)] scale plasma simulation on a desktop computer. Also, the LH full wave simulation of an ITER scale plasma was demonstrated for the first time with moderate increase in the problem size. In addition, the flexibility of the FEM approach has been exploited to address issues of antenna-plasma coupling in the LH and ion cyclotron range of frequencies (ICRF). Techniques using the FEM package for this purpose were validated on the traditional grill antenna and have been applied to the interdigital-line antenna of LH wave. Application to the near field analysis of the new Alcator C-Mod [I. H. Hutchinson, R. Boivin, F. Bombarda et al., Phys. Plasmas 1, 1511 (1994)] ICRF antenna is in progress.
70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗