Assessment of the impact of kinetic effect of ion parallel heat conduction on DEMO relevant SOL plasma using integrated SOL-divertor code SONIC

Author(s):  
Yuki Homma

Abstract In plasmas of relatively lower collisionality, such as scrape-off layer (SOL) of fusion tokamak device, parallel heat conductivity of plasma ion becomes smaller than expected by the classical Spitzer-Harm model due to nonlocal kinetic effect. We have assessed, by simulation, impact and role of such kinetic effect of ion heat conductivity (abbreviated by ion KE in this paper) on DEMO relevant tokamak SOL plasma, supposing Japanese demonstration tokamak reactor concept JA DEMO. A series of test simulation, where the ion KE is modeled by a widely used Free-streaming energy (FSE) limited model, has demonstrated the following significant impact of the ion KE on JA DEMO SOL plasma at the baseline operation scenario: (1) the ion KE decreases the ion parallel heat flux density around X-point and further upstream of low field side (LFS) area along the separatrix, where the parallel collisionality tends to decrease due to combination of higher temperature, lower density (i.e. longer mean free path of ion collisions) and higher temperature gradient (shorter characteristic length). Up to 40-60 % of decrease, compared to the case w/o ion KE, is observed among the tested cases where the ion KE level, specified by parameter αi in the FSE-limited model, is scanned over the possible range 0.2 < αi < 2.0. (2) The ion KE leads to significant increase in the ion temperature Ti (up to 600 % of increase among the tested cases) and significant decrease in the ion density ni (up to -80 % of decrease among the tested cases), widely over SOL upstream. By energy balance analysis, it has been suggested that the ion KE affects the upstream ni and Ti, respectively by power of 0.4 and -0.4 of the flux limiting factor, around the separatrix upstream as far as spatial change in plasma parameters are moderate. The results of this study serve as a fundamental assessment of the ion KE for DEMO relevant SOL plasma, clarifying the need of further sophistication of the modeling toward quantitaive prediction.

2020 ◽  
Vol 12 (24) ◽  
pp. 10261
Author(s):  
Yaroslav Vyklyuk ◽  
Milan M. Radovanović ◽  
Gorica Stanojević ◽  
Marko D. Petrović ◽  
Nina B. Ćurčić ◽  
...  

The impact of solar activity on environmental processes is difficult to understand and complex for empirical modeling. This study aimed to establish forecast models of the meteorological conditions in the forest fire areas based on the solar activity parameters applying the neural networks approach. During July and August 2018, severe forest fires simultaneously occurred in the State of California (USA), Portugal, and Greece. Air temperature and humidity data together with solar parameters (integral flux of solar protons, differential electron flux and proton flux, solar wind plasma parameters, and solar radio flux at 10.7 cm data) were used in long short-term memory (LSTM) recurrent neural network ensembles. It is found that solar activity mostly affects the humidity for two stations in California and Portugal (an increase in the integral flux of solar protons of > 30 MeV by 10% increases the humidity by 3.25%, 1.65%, and 1.57%, respectively). Furthermore, an increase in air temperature of 10% increases the humidity by 2.55%, 2.01%, and 0.26%, respectively. It is shown that temperature is less sensitive to changes in solar parameters but depends on previous conditions (previous increase of 10% increases the current temperature by 0.75%, 0.34%, and 0.33%, respectively). Humidity in Greece is mostly impacted by solar flux F10.7 cm and previous values of humidity. An increase in these factors by 10% will lead to a decrease in the humidity of 3.89% or an increase of 1.31%, while air temperature mostly depends on ion temperature. If this factor increases by 10%, it will lead to air temperature rising by 0.42%.


2012 ◽  
Vol 78 (3) ◽  
pp. 289-294 ◽  
Author(s):  
MIKHAIL Y. PUSTYLNIK ◽  
MARKUS H. THOMA ◽  
GREGOR E. MORFIŁL ◽  
RAINER GRIMM ◽  
CHRISTIAN HOCK

AbstractComplex plasmas are low-temperature plasmas containing micron-sized particles (microparticles) such as dust grains. These are present in astrophysical systems (comets, molecular clouds, et al.) and in technological applications (microchip production by plasma etching, deposition of solar cells, et al.). Complex plasmas are also of interest in basic science because these are often used as models for many other strongly coupled many-body systems in solid state, fluid, or plasma physics. Since gravity has a strong influence on the microparticle component, experiments under microgravity (parabolic flights, sounding rockets, International Space Station (ISS)) are performed. Interaction between microparticles depends on plasma parameters such as ion density or ion temperature. Also, the presence of microparticles may change the properties of background plasma. Therefore, the background plasma needs to be characterized to provide adequate interpretation of the microgravity experiments. For this purpose a dedicated high-speed diagnostic system has been set up.


BMJ Open ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. e043863
Author(s):  
Jingyuan Wang ◽  
Ke Tang ◽  
Kai Feng ◽  
Xin Lin ◽  
Weifeng Lv ◽  
...  

ObjectivesWe aim to assess the impact of temperature and relative humidity on the transmission of COVID-19 across communities after accounting for community-level factors such as demographics, socioeconomic status and human mobility status.DesignA retrospective cross-sectional regression analysis via the Fama-MacBeth procedure is adopted.SettingWe use the data for COVID-19 daily symptom-onset cases for 100 Chinese cities and COVID-19 daily confirmed cases for 1005 US counties.ParticipantsA total of 69 498 cases in China and 740 843 cases in the USA are used for calculating the effective reproductive numbers.Primary outcome measuresRegression analysis of the impact of temperature and relative humidity on the effective reproductive number (R value).ResultsStatistically significant negative correlations are found between temperature/relative humidity and the effective reproductive number (R value) in both China and the USA.ConclusionsHigher temperature and higher relative humidity potentially suppress the transmission of COVID-19. Specifically, an increase in temperature by 1°C is associated with a reduction in the R value of COVID-19 by 0.026 (95% CI (−0.0395 to −0.0125)) in China and by 0.020 (95% CI (−0.0311 to −0.0096)) in the USA; an increase in relative humidity by 1% is associated with a reduction in the R value by 0.0076 (95% CI (−0.0108 to −0.0045)) in China and by 0.0080 (95% CI (−0.0150 to −0.0010)) in the USA. Therefore, the potential impact of temperature/relative humidity on the effective reproductive number alone is not strong enough to stop the pandemic.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
I. S. Elkamash ◽  
I. Kourakis

AbstractA one-dimensional multifluid hydrodynamic model has been adopted as basis for an investigation of the role of suprathermal electrons on the wave breaking amplitude limit for electrostatic excitations propagating in an electronegative plasma. A three-component plasma is considered, consisting of two inertial cold ion populations of opposite signs, evolving against a uniform background of (non-Maxwellian) electrons. A kappa-type (non-Maxwellian) distribution function is adopted for the electrons. By employing a traveling wave approximation, the first integral for the fluid-dynamical system has been derived, in the form of a pseudo-energy balance equation, and analyzed. The effect of intrinsic plasma parameters (namely the ion density ratio, the ion mass ratio, and the superthermal index of the nonthermal electrons) on the wave breaking amplitude limit is explored, by analyzing the phase space topology of the associated pseudopotential function. Our results are relevant to particle acceleration in Space environments and to recent experiments based on plasma-based accelerator schemes, where the simultaneous presence of negative ions and nonthermal electrons may be observed.


1969 ◽  
Vol 3 (2) ◽  
pp. 161-178 ◽  
Author(s):  
E. W. Billington

The primary quantities characterizing the electricaJ carriers of a flowing plasma in a low density wind tunnel have been determined from measurements using electrostatic probes immersed in the plasma. With the exception of the ion temperature, the plasma parameters have been obtained from the current—voltage characteristics of two types of single electrode probe. The probes consist of a cylinder, the major axis of which is aligned parallel to the flow of the plasma, and a disk, the exposed surface of which is normal to the direction of flow. Experiments with a double electrode probe consisting of a disk-shaped collector electrode which is screened from direct exposure to the plasma by a fine wire mesh, grid electrode, made it possible to obtain current—voltage characteristics with the ion and electron components separated from one another. From the current—voltage characteristic corresponding to collection of ions, using the screen grid probe, values of the ion temperature and drift velocity have been obtained. The measurements have been made at various points along the centre line of flow, for one particular value of the flow rate using argon as the test gas. For a given position of the probes, one value of the ion temperature has been evaluated, together with two independent values of each of the other primary quantities characterizing the electrical carriers of a flowing plasma. Each pair of values agree satisfactorily amongst themselves, good agreement being generally obtained between probe theory and experiment.


1998 ◽  
Vol 59 (3) ◽  
pp. 505-536 ◽  
Author(s):  
LINDSEY D. THORNHILL ◽  
PRATEEN V. DESAI

Asymptotically matched solutions for electron and ion density, electron and ion velocity, and electric potential are obtained in the boundary region of a dense low-temperature plasma adjacent to perfectly absorbing walls – walls that absorb, without reflection, incident electrons and ions. Leading-order composite solutions, valid throughout the boundary region, are constructed from solutions in three subdomains distinguished by different physical length scales: the geometric length, the ion mean free path and the Debye length. The composite solutions are used to assess the impact of electron–ion recombination in the ionization nonequilibrium region on sheath and presheath profiles, and on quantities evaluated at the wall. While, at leading order, the velocity profiles throughout the boundary region are not influenced by recombination, the density and potential profiles are significantly altered when recombination is included. These results show that the region of rapid change in these profiles lies closer to the wall when recombination is explicitly included in the model. The influence of recombination on the presheath potential, and consequently the wall potential, is found to scale as the natural logarithm of the recombination length. The broadening of the density profile results in a larger flux of ions accelerating through the sheath and impacting on the wall. The influence of recombination on the ion power flux to the wall is found to scale with the inverse recombination length. This scaling influences the prediction of surface erosion rates in technological applications that utilize these plasmas.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shinichiro Hatta ◽  
Ko Obayashi ◽  
Hiroshi Okuyama ◽  
Tetsuya Aruga

AbstractWhile the van der Waals (vdW) interface in layered materials hinders the transport of charge carriers in the vertical direction, it serves a good horizontal conduction path. We have investigated electrical conduction of few quintuple-layer (QL) $$\hbox {Bi}_2\hbox {Te}_3$$ Bi 2 Te 3 films by in situ four-point probe conductivity measurement. The impact of the vdW (Te–Te) interface appeared as a large conductivity increase with increasing thickness from 1 to 2 QL. Angle-resolved photoelectron spectroscopy and first-principles calculations reveal the confinement of bulk-like conduction band (CB) state into the vdW interface. Our analysis based on the Boltzmann equation showed that the conduction of the CB has a long mean free path compared to the surface-state conduction. This is mainly attributed to the spatial separation of the CB electrons and the donor defects located at the Bi sites.


2021 ◽  
Author(s):  
Livia Casali ◽  
David Eldon ◽  
Adam G McLean ◽  
Tom H Osborne ◽  
Anthony W Leonard ◽  
...  

Abstract A comparative study of nitrogen versus neon has been carried out to analyze the impact of the two radiative species on power dissipation, SOL impurity distribution, divertor and pedestal characteristics. The experimental results show that N remains compressed in the divertor, thereby providing high radiative losses without affecting the pedestal profiles and displacing carbon as dominant radiator. Neon, instead, radiates more upstream than N thus reducing the power flux through the separatrix leading to a reduced ELM frequency and compression in the divertor. A significant amount of neon is measured in the plasma core leading to a steeper density gradient. The different behaviour between the two impurities is confirmed by SOLPS-ITER modelling which for the first time at DIII-D includes multiple impurity species and a treatment of full drifts, currents and neutral-neutral collisions. The impurity transport in the SOL is studied in terms of the parallel momentum balance showing that N is mostly retained in the divertor whereas Ne leaks out consistent with its higher ionization potential and longer mean free path. This is also in agreement with the enrichment factor calculations which indicate lower divertor enrichment for neon. The strong ionization source characterizing the SAS divertor causes a reversal of the main ions and impurity flows. The flow reversal together with plasma drifts and the effect of the thermal force contribute significantly in the shift of the impurity stagnation point affecting impurity leakage. This work provides a demonstration of the impurity leakage mechanism in a closed divertor structure and the consequent impact on pedestal. Since carbon is an intrinsic radiator at DIII-D, in this paper we have also demonstrated the different role of carbon in the N vs Ne seeded cases both in the experiments and in the numerical modeling. Carbon contributes more when neon seeding is injected compared to when nitrogen is used. Finally, the results highlight the importance of accompanying experimental studies with numerical modelling of plasma flows, drifts and ionization profile to determine the details of the SOL impurity transport as the latter may vary with changes in divertor regime and geometry. In the cases presented here, plasma drifts and flow reversal caused by high level of closure in the slot upper divertor at DIII-D play an important role in the underlined mechanism.


2021 ◽  
Author(s):  
Priya kaushal ◽  
Tarun Chaudhary ◽  
Gargi Khanna

Abstract The present work is based on the computational study of MoS2 monolayer and effect of tensile strain on its atomic level structure. The bandgap for MoS2 monolayer, defected MoS2 monolayer and Silicon-doped monolayer are 1.82 eV (direct bandgap), 0.04 (indirect bandgap) and 1.25eV (indirect bandgap), respectively. The impact of tensile strain (0-0.7%) on the bandgap and effective mass of charge carriers of these three MoS2 structure has been investigated. The bandgap decrease of 5.76%, 31.86% and 6.03% has been observed in the three structures for biaxial strain while the impact of uniaxial strain is quite low. The impact of higher temperature on the bandgap under biaxial tensile strain has been also analyzed in this paper. These observations are extremely important for 2D material-based research for electronic applications.


2018 ◽  
Vol 145 ◽  
pp. 03004
Author(s):  
Polya Dobreva ◽  
Olga Nitcheva ◽  
Monio Kartalev

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.


Sign in / Sign up

Export Citation Format

Share Document