Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

2021 ◽  
Author(s):  
Shengyu Shi ◽  
Jiale Chen ◽  
Clarisse Bourdelle ◽  
Xiang Jian ◽  
Tomas Odstrcil ◽  
...  
Keyword(s):  
Density Profile ◽  
Turbulent Diffusion ◽  
High Performance ◽  
Electron Cyclotron Resonance ◽  
Transport Coefficients ◽  
Linear Instability ◽  
Electron Cyclotron Resonance Heating ◽  
Plasma Parameters ◽  
Turbulent Diffusion Coefficient ◽  
Inductive Discharge

Abstract The behavior of heavy/high-Z impurity tungsten (W) in an improved high-performance fully non-inductive discharge on EAST with ITER-like divertor (ILD) is analyzed. It is found that W could be well controlled. The causes of no W accumulation are clarified by analyzing the background plasma parameters and modeling the W transport. It turns out that the electron temperature (T_e) and its gradient are usually high while the toroidal rotation and density peaking of the bulk plasma are small. In this condition, the modeled W turbulent diffusion coefficient is big enough to offset the total turbulent and neoclassical pinch, so that W density profile for zero particle flux will not be very peaked. Combining NEO and TGLF for the W transport coefficient and the impurity transport code STRAHL, not only the core W density profile is predicted but also the radiated information mainly produced by W in the experiment can be closely reconstructed. At last, the physics of controlling W accumulation by electron cyclotron resonance heating (ECRH) is illustrated considering the effects of changed T_e by ECRH on ionization balance and transport of W. It shows that the change of ionization and recombination balance by changed T_e is not enough to explain the experimental observation of W behavior, which should be attributed to the changed W transport. By comparing the W transport coefficients in two kinds of plasmas with different T_e profiles, it is shown that high T_e and its gradient play a key role to generate large turbulent diffusion through increasing the growth rate of linear instability so that W accumulation is prevented.

Electron Cyclotron Resonance Heating of Plasma in the Gas Dynamic Trap

2014 ◽  
Vol 9 (2) ◽  
pp. 13-21
Author(s):  
Aleksandr Solomakhin ◽  
Petr Bagryansky ◽  
Yuriy Kovalenko ◽  
Valeriy Savkin ◽  
Dmitriy Yakovlev
Keyword(s):  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Plasma Heating ◽  
Electron Cyclotron ◽  
Electron Cyclotron Resonance Heating ◽  
Total Power ◽  
Plasma Parameters ◽  
Experimental Conditions ◽  
Microwave Beam ◽  
Gas Dynamic

Electron cyclotron resonance plasma heating (ECRH) system has been recently installed on the gas dynamic trap (GDT) magnetic mirror. Two microwave beams are injected into the plasma at an angle of 36° with respect to the machine axis in a form of extraordinary (X) waves which are subsequently absorbed in the first harmonic cyclotron resonance. Each microwave beam is generated by a Buran-A type 450 kW/54.5 GHz gyrotron. The article reports on the first microwave injection experiments with limited total power of 300 kW. Adjustment of experimental conditions and magnetic field reconfiguration resulted in an increased diamagnetic signal, electron temperature and other plasma parameters

Hollow Density Profile on Electron Cyclotron Resonance Heating JFT-2M Plasma

1998 ◽  
Vol 37 (Part 1, No. 10) ◽  
pp. 5735-5741 ◽  
Author(s):  
Toshihiko Yamauchi ◽  
Katsumichi Hoshino ◽  
Hisato Kawashima ◽  
Toshihide Ogawa ◽  
Tomohide Kawakami ◽  
...  
Keyword(s):  
Density Profile ◽  
Cyclotron Resonance ◽  
Electron Cyclotron Resonance ◽  
Electron Cyclotron ◽  
Electron Cyclotron Resonance Heating

scholarly journals Validation of low-Z impurity transport theory using boron perturbation experiments at ASDEX Upgrade

2021 ◽  
Author(s):  
Rachael M McDermott ◽  
Clemente Angioni ◽  
Marco Cavedon ◽  
Athina Kappatou ◽  
Ralph Dux ◽  
...  
Keyword(s):  
Particle Flux ◽  
Transport Theory ◽  
Electron Cyclotron Resonance ◽  
Transport Coefficients ◽  
Electron Cyclotron Resonance Heating ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Density Profiles ◽  
Boron Particle ◽  
Impurity Transport

Abstract An experimental technique has been developed at ASDEX Upgrade (AUG) to separately identify the diffusive and convective components of the boron particle flux. Using this technique a database of B transport coefficients has been assembled that shows that the normalized ion temperature gradient (R/LTi) is the strongest organizing parameter for both the B diffusion and convection and large R/LTi is a necessary ingredient to obtain hollow B density profiles in AUG. This database also shows that large changes in the applied neutral beam injection (NBI) have a relatively small impact on impurity transport compared to similar changes in electron cyclotron resonance heating (ECRH). Even low levels of ECRH power dramatically increase both the diffusive and convective fluxes and lead to peaking of the impurity density profile. Comparisons to a combination of neoclassical and quasi-linear gyrokinetic simulations show good agreement in the measured and predicted diffusion coefficients. The outward convection measured in NBI dominated plasmas, however, is not well captured by the simulations, despite the inclusion of fast ions. In contrast, the convection is reasonably well reproduced for plasmas with flat or peaked boron density profiles. This dataset provides an excellent experimental validation of the non-monotonic, predicted, convective-particle-flux created by the combination of pure-pinch, thermo-diffusion, and roto-diffusion. In addition, this dataset demonstrates a non-monotonic dependence of the experimental particle diffusivity to ion heat conductivity (D/χi) in qualitative agreement with theoretical predictions.

Direct Inverse Control for ECRH Voltage Based on ICA-CMAC

2011 ◽  
Vol 268-270 ◽  
pp. 1755-1758
Author(s):  
Xiao Ping Luo ◽  
Peng Ying Du ◽  
Ying Qi Ge
Keyword(s):  
Nonlinear System ◽  
Power Supply ◽  
Cyclotron Resonance ◽  
Control Experiment ◽  
Electron Cyclotron Resonance ◽  
Electron Cyclotron Resonance Heating ◽  
Quick Response ◽  
High Voltage Power Supply ◽  
Inverse Control ◽  
Intelligent Controller

The negative high-voltage power supply of Electron Cyclotron Resonance Heating (ECRH) is a nonlinear system with serve sensitivity and it is not well for traditional controller to meet restrict demand on stability and quick response. Based on the concept of credit a novel CMAC is designed to accelerate the convergence of traditional CMAC and also is used as an intelligent controller for the power of ECRH based on the idea on direct inverse control. Experiment results show that ICA-CMAC can control the power of ECRH well with shorter settling time and less CPU consumption thus the validity of ICA-CMAC is determined.

Understanding core heavy impurity transport in a hybrid discharge on EAST

2021 ◽  
Author(s):  
Shengyu Shi ◽  
Jiale Chen ◽  
Clarisse Bourdelle ◽  
Xiang Jian ◽  
Tomas Odstrcil ◽  
...  
Keyword(s):  
Density Profile ◽  
Central Region ◽  
Turbulent Transport ◽  
Accumulation Process ◽  
Plasma Parameters ◽  
Toroidal Rotation ◽  
The Core ◽  
Impurity Transport ◽  
Accumulation Phase ◽  
Bulk Plasma

Abstract The behavior of heavy/high-Z impurity tungsten (W) in the core of hybrid (high normalized beta β_N plasmas) scenario on EAST with ITER-like divertor (ILD) is analyzed. W accumulation is often observed and seriously degrades the plasma performance (Xiang Gao et al 2017 Nucl. Fusion 57 056021). The dynamics of the W accumulation process of a hybrid discharge are examined considering the concurrent evolution of the background plasma parameters. It turns out that the toroidal rotation and density peaking of the bulk plasma are usually large in the central region, which is particularly prone to the W accumulation. A time slice during the W accumulation phase is modeled, accounting for both neoclassical and turbulent transport components of W, through NEO with poloidal asymmetry effects induced by toroidal rotation, and TGLF, respectively. This modeling reproduces the experimental observations of W accumulation and identifies the neoclassical inward convection/pinch velocity of W due to the large density peaking of the bulk plasma and toroidal rotation in the central region as one of the main reasons for the W accumulation. In addition, the NEO+TGLF+STRAHL modeling can not only predict the core W density profile but also closely reconstruct the radiated information mainly produced by W in the experiment.

Thermoelectrics by Computational Design: Progress and Opportunities

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
Boris Kozinsky ◽  
David J. Singh
Keyword(s):  
First Principles ◽  
High Performance ◽  
Materials Science ◽  
Phonon Scattering ◽  
Transport Coefficients ◽  
Computational Design ◽  
Science Volume ◽  
Annual Review ◽  
Publication Date ◽  
Boltzmann Transport

The performance of thermoelectric materials is determined by their electrical and thermal transport properties that are very sensitive to small modifications of composition and microstructure. Discovery and design of next-generation materials are starting to be accelerated by computational guidance. We review progress and challenges in the development of accurate and efficient first-principles methods for computing transport coefficients and illustrate approaches for both rapid materials screening and focused optimization. Particularly important and challenging are computations of electron and phonon scattering rates that enter the Boltzmann transport equations, and this is where there are many opportunities for improving computational methods. We highlight the first successful examples of computation-driven discoveries of high-performance materials and discuss avenues for tightening the interaction between theoretical and experimental materials discovery and optimization. Expected final online publication date for the Annual Review of Materials Science, Volume 51 is August 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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