scholarly journals Simulating the impact of charge exchange on beam ions in MAST-U

2022 ◽  
Author(s):  
Patrik Ollus ◽  
Robert James Akers ◽  
Bethany Colling ◽  
Hana El-Haroun ◽  
David Keeling ◽  
...  
Keyword(s):  
Charge Exchange ◽  
Plasma Heating ◽  
Current Drive ◽  
Beam Power ◽  
Fusion Plasmas ◽  
Vacuum Vessel ◽  
Noticeable Increase ◽  
Slowing Down ◽  
Fast Ions ◽  
The Impact

Abstract A model for simulating charge exchange (CX) of fast ions with background atoms in magnetically confined fusion plasmas has been implemented in the ASCOT orbit-following code. The model was verified by comparing simulated reaction mean free paths to analytical values across a range of fusion-relevant parameters. ASCOT was used to simulate beam ions slowing down in the presence of CX reactions in a MAST-U target scenario. ASCOT predicts the CX-induced loss of beam power to be 22%, which agrees to within 15% with the TRANSP prediction. Because of CX, plasma heating and current drive by beam ions are strongly reduced towards the edge. However, an overall lower but noticeable increase of up to 20% in current drive is predicted closer to the core. The simulated deposition of fast CX atoms on the wall is concentrated around the outer midplane, with estimated peak power loads of 70–80 kWm-2 on the central poloidal field coils (P5) and the vacuum vessel wall between them. This analysis demonstrates that ASCOT can be used to simulate fast ions in fusion plasmas where CX reactions play a significant role, e.g., in spherical tokamaks and stellarators.

scholarly journals Validating modeling assumptions of alpha particles in electrostatic turbulence

2015 ◽  
Vol 81 (3) ◽  
Author(s):  
G. J. Wilkie ◽  
I. G. Abel ◽  
E. G. Highcock ◽  
W. Dorland
Keyword(s):  
Particle Flux ◽  
Magnitude Estimate ◽  
High Energy ◽  
Alpha Particles ◽  
Fusion Plasmas ◽  
Usual Practice ◽  
Slowing Down ◽  
Fast Ions ◽  
Low Concentrations ◽  
Order Of Magnitude

To rigorously model fast ions in fusion plasmas, a non-Maxwellian equilibrium distribution must be used. In this work, the response of high-energy alpha particles to electrostatic turbulence has been analyzed for several different tokamak parameters. Our results are consistent with known scalings and experimental evidence that alpha particles are generally well confined: on the order of several seconds. It is also confirmed that the effect of alphas on the turbulence is negligible at realistically low concentrations, consistent with linear theory. It is demonstrated that the usual practice of using a high-temperature Maxwellian, while previously shown to give an adequate order-of-magnitude estimate of the diffusion coefficient, gives incorrect estimates for the radial alpha particle flux, and a method of correcting it in general is provided. Furthermore, we see that the timescales associated with collisions and transport compete at moderate energies, calling into question the assumption that alpha particles remain confined to a flux surface that is used in the derivation of the slowing-down distribution.

scholarly journals Characteristics of Cr-B Coatings Produced on Vanadis® 6 Tool Steel Using Laser Processing

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2621
Author(s):  
Aneta Bartkowska
Keyword(s):  
Corrosion Resistance ◽  
Tool Steel ◽  
Laser Processing ◽  
Chemical Elements ◽  
Steel Substrate ◽  
Processing Parameters ◽  
Beam Power ◽  
Laser Beam Power ◽  
High Microhardness ◽  
The Impact

The paper presents the results of a study of the microstructure, chemical composition, microhardness and corrosion resistance of Cr-B coatings produced on Vanadis 6 tool steel. In this study, chromium and boron were added to the steel surface using a laser alloying process. The main purpose of the study was to determine the impact of those chemical elements on surface properties. Chromium and boron as well as their mixtures were prepared in various proportions and then were applied on steel substrate in the form of precoat of 100 µm thickness. Depending on the type of precoat used and laser processing parameters, changes in microstructure and properties were observed. Coatings produced using precoat containing chromium and boron mixture were characterized by high microhardness (900 HV0.05–1300 HV0.005) while maintaining good corrosion resistance. It was also found that too low laser beam power contributed to the formation of cracks and porosity.

scholarly journals The impact of gross domestic product on the financing and investment efficiency of China’s commercial banks

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Zhen Shi ◽  
Shijiong Qin ◽  
Yung-ho Chiu ◽  
Xiaoying Tan ◽  
Xiaoli Miao
Keyword(s):  
Gross Domestic Product ◽  
Commercial Banks ◽  
Domestic Product ◽  
Investment Efficiency ◽  
Internal Factors ◽  
Slowing Down ◽  
Return On Capital ◽  
Overall Efficiency ◽  
Financing And Investment ◽  
The Impact

AbstractChina’s commercial banks have developed at a very rapid speed in recent decades. However, with global economic development slowing down, the impact of gross domestic product growth as an exogenous factor cannot be ignored. Most existing studies only consider the internal factors of banks, and neglect their external economic factors. This study thus adopts an undesirable dynamic slacks-based measure under an exogenous model in combination with the Kernel density curve to explore the efficiency of state-owned commercial banks (SOCBs), joint-stock commercial banks (JSCBs), and urban commercial banks (UCBs) in China from 2012 to 2018. The results show that SOCBs have the highest overall efficiency, followed by JSCBs, then UCBs. The efficiencies of SOCBs, JSCBs, and UCBs in the financing stage are greater than those in the investment stage, indicating that the latter stage brings down overall efficiency. Thus, all commercial banks need to focus on the efficiency of non-performing loans and return on capital. Finally, SOCBs need to strengthen internal controls, reduce non-performing loans and improve return on capital. JSCBs should actively expand its business while controlling costs, and UCBs should optimize its management.

Current Drive and Plasma Heating by Electron Bernstein Waves in MAST

2009 ◽  
Author(s):  
V. Shevchenko ◽  
A. Saveliev ◽  
Volodymyr Bobkov ◽  
Jean-Marie Noterdaeme
Keyword(s):  
Plasma Heating ◽  
Current Drive ◽  
Bernstein Waves

Production of plasma vortices by lower-hybrid waves

1981 ◽  
Vol 26 (2) ◽  
pp. 359-367 ◽  
Author(s):  
M. Y. Yu ◽  
P. K. Shukla ◽  
H. U. Rahman
Keyword(s):  
Plasma Heating ◽  
Finite Amplitude ◽  
Current Drive ◽  
Lower Hybrid ◽  
Magnetic Fluctuations ◽  
Field Diffusion ◽  
Modulational Instabilities ◽  
Hybrid Waves ◽  
Plasma Vortices ◽  
Lower Hybrid Waves

Nonlinear excitation of electrostatic and magnetostatic zero-frequency modes by finite-amplitude lower-hybrid waves is considered. It is found that modulational instabilities can give rise to enhanced plasma vortices. Dispersion relations, as well as analytical expressions for the growth rates, are obtained. The enhanced vortices may cause anomalous cross-field diffusion which can affect plasma confinement in tokamak devices when lower-hybrid waves are used for plasma heating or current drive. We found that magnetic fluctuations associated with the parametrically driven magnetostatic mode are of particular importance in tokamak plasmas.

Analytical approximation of cross-section effects on charge exchange spectra observed in hot fusion plasmas

1995 ◽  
Vol 37 (2) ◽  
pp. 71-94 ◽  
Author(s):  
M von Hellermann ◽  
P Breger ◽  
J Frieling ◽  
R Konig ◽  
W Mandl ◽  
...  
Keyword(s):  
Cross Section ◽  
Charge Exchange ◽  
Analytical Approximation ◽  
Fusion Plasmas

Changes in mechanisms and intensity of Western U.S. floods, 1960-2013

2021 ◽  
Author(s):  
Jessica Fayne ◽  
Huilin Huang ◽  
Mike Fischella ◽  
Yufei Liu ◽  
Zhaoxin Ban ◽  
...  
Keyword(s):  
Extreme Precipitation ◽  
Large Scale ◽  
Critical Factor ◽  
Flood Frequency ◽  
Atmospheric Rivers ◽  
Convective Storms ◽  
Noticeable Increase ◽  
Complex Interactions ◽  
Different Types ◽  
The Impact

<p>Extreme precipitation, a critical factor in flooding, has selectively increased with warmer temperatures in the Western U.S. Despite this, the streamflow measurements have captured no noticeable increase in large-scale flood frequency or intensity. As flood studies have mostly focused on specific flood events in particular areas, analyses of large-scale floods and their changes have been scarce. For floods during 1960-2013, we identify six flood generating mechanisms (FGMs) that are prominent across the Western U.S., including atmospheric rivers and non-atmospheric rivers, monsoons, convective storms, radiation-driven snowmelt, and rain-on-snow, in order to identify to what extent different types of floods are changing based on the dominant FGM. The inconsistency between extreme precipitation and lack of flood increase suggests that the impact of climate change on flood risk has been modulated by hydro-meteorological and physiographic processes such as sharp increases in temperature that drive increased evapotranspiration and decreased soil moisture. Our results emphasize the importance of FGMs in understanding the complex interactions of flooding and climatic changes and explain the broad spatiotemporal changes that have occurred across the vast Western U.S. for the past 50 years.</p>

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