Numerical modeling of pedestal stability and broadband turbulence of wide-pedestal QH-mode plasmas on DIII-D

2022 ◽  
Author(s):  
Zeyu Li ◽  
Xi Chen ◽  
Christopher M Muscatello ◽  
Keith H Burrell ◽  
Xueqiao Xu ◽  
...  
Keyword(s):  
Fluid Model ◽  
Operation Mode ◽  
High Energy ◽  
Alfven Wave ◽  
Rotation Direction ◽  
Diamagnetic Drift ◽  
Spatial Locations ◽  
Trapped Electron ◽  
Possible Cause ◽  
Drift Direction

Abstract Wide pedestal Quiescent High confinement (QH) mode discovered on DIII-D in recent years is a stationary and quiescent H-mode with the pedestal width exceeding EPED prediction by at least 25%. Its characteristics, such as low rotation, high energy confinement and ELM-free operation, make it an attractive operation mode for future reactors. Linear and nonlinear simulations using BOUT++ reduced two fluid MHD model are carried out to investigate the bursty broadband turbulence often observed in the edge of wide-pedestal QH-mode plasmas. Two kinds of MHD-scale instabilities in different spatial locations within the pedestal were found in the simulations: one mild peeling-ballooning (PB) mode (γ_PB<0.04ω_A) located near the minimum in Er well propagating in ion diamagnetic drift direction; and one drift-Alfvén wave (DAW) locates at smaller radius compared to Er well propagating in the electron diamagnetic drift direction and unstable only when the parallel electron dynamics is included in the simulation. The coupling between drift wave and shear Alfvén wave provides a possible cause of the experimentally observed local profile flattening in the upper-pedestal. The rotation direction, mode location, as well as the wavenumber of these two modes from BOUT++ simulations agree reasonably well with the experimental measurements, while the lack of quantitatively agreement is likely due to the lack of trapped electron physics in current fluid model. This work presents improved physics understanding of the pedestal stability and turbulence dynamics for wide-pedestal QH-mode.

scholarly journals Proof of concept of wastewater treatment via passive aeration SND using a novel zeolite amended biofilm reactor

2018 ◽  
Vol 78 (10) ◽  
pp. 2204-2213 ◽  
Author(s):  
Liang Cheng ◽  
Raphael Marie-Guillaume Flavigny ◽  
Md Iqbal Hossain ◽  
Wipa Charles ◽  
Ralf Cord-Ruwisch
Keyword(s):  
Oxygen Supply ◽  
Energy Requirement ◽  
Operation Mode ◽  
High Energy ◽  
Biofilm Reactor ◽  
Low Energy ◽  
Treated Wastewater ◽  
Synthetic Wastewater ◽  
Bulk Solution ◽  
Nutrient Removal Efficiency

Abstract The current paper describes a novel passive aeration simultaneous nitrification and denitrification (PASND) zeolite amended biofilm reactor that removes organic carbon and nitrogen from wastewater with low-energy consumption. Next to the ammonium oxidizing bacteria (AOB), this reactor contained naturally enriched glycogen accumulating organisms (GAOs) and zeolite powder to initially adsorb BOD (acetate) and ammonium (NH4+-N) from synthetic wastewater under anaerobic conditions. Draining of the treated wastewater exposed the biofilm directly to air enabling low-energy oxygen supply by passive aeration. This allowed the adsorbed ammonium to be oxidized by the AOB and the produced nitrite and nitrate to be reduced simultaneously by the GAOs using the adsorbed BOD (stored as PHAs) as carbon source. Overall, with an operation mode of 1 h anaerobic and 4 h aerobic phase, the nutrient removal efficiency after single treatment was about 94.3% for BOD and 72.2% for nitrogen (NH4+-N). As high-energy aeration of the bulk solution for oxygen supply is completely avoided, the energy requirement of the proposed PASND biofilm reactor can be theoretically cut down to more than 50% compared to the traditional activated sludge process.

scholarly journals Alfvén waves in the magnetosphere generated by shock wave / plasmapause interaction

2019 ◽  
Vol 5 (2) ◽  
pp. 9-14
Author(s):  
Анатолий Леонович ◽  
Anatoliy Leonovich ◽  
Цюган Цзун ◽  
Qiugang Zong ◽  
Даниил Козлов ◽  
...  
Keyword(s):  
Shock Wave ◽  
Alternative Hypothesis ◽  
Contact Region ◽  
High Energy ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
High Energy Particle ◽  
Secondary Source ◽  
Wave Passage

We study Alfvén waves generated in the magnetosphere during the passage of an interplanetary shock wave. After shock wave passage, the oscillations with typical Alfvén wave dispersion have been detected in spacecraft observations inside the magnetosphere. The most frequently observed oscillations are those with toroidal polarization; their spatial structure is described well by the field line resonance (FLR) theory. The oscillations with poloidal polarization are observed after shock wave passage as well. They cannot be generated by FLR and cannot result from instability of high-energy particle fluxes because no such fluxes were detected at that time. We discuss an alternative hypothesis suggesting that resonant Alfvén waves are excited by a secondary source: a highly localized pulse of fast magnetosonic waves, which is generated in the shock wave/plasmapause contact region. The spectrum of such a source contains oscillation harmonics capable of exciting both the toroidal and poloidal resonant Alfvén waves.

scholarly journals Reduced models accounting for parallel magnetic perturbations: gyrofluid and finite Larmor radius–Landau fluid approaches

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
E. Tassi ◽  
P. L. Sulem ◽  
T. Passot
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Low Frequency ◽  
Wave Model ◽  
Plasma Phys ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Closure Relation ◽  
Reduced Models ◽  
Finite Larmor Radius

Reduced models are derived for a strongly magnetized collisionless plasma at scales which are large relative to the electron thermal gyroradius and in two asymptotic regimes. One corresponds to cold ions and the other to far sub-ion scales. By including the electron pressure dynamics, these models improve the Hall reduced magnetohydrodynamics (MHD) and the kinetic Alfvén wave model of Boldyrev et al. (2013 Astrophys. J., vol. 777, 2013, p. 41), respectively. We show that the two models can be obtained either within the gyrofluid formalism of Brizard (Phys. Fluids, vol. 4, 1992, pp. 1213–1228) or as suitable weakly nonlinear limits of the finite Larmor radius (FLR)–Landau fluid model of Sulem and Passot (J. Plasma Phys., vol 81, 2015, 325810103) which extends anisotropic Hall MHD by retaining low-frequency kinetic effects. It is noticeable that, at the far sub-ion scales, the simplifications originating from the gyroaveraging operators in the gyrofluid formalism and leading to subdominant ion velocity and temperature fluctuations, correspond, at the level of the FLR–Landau fluid, to cancellation between hydrodynamic contributions and ion finite Larmor radius corrections. Energy conservation properties of the models are discussed and an explicit example of a closure relation leading to a model with a Hamiltonian structure is provided.

scholarly journals A two-fluid model describing the finite-collisionality, stationary Alfvén wave in anisotropic plasma

2008 ◽  
Vol 15 (6) ◽  
pp. 957-964 ◽  
Author(s):  
S. M. Finnegan ◽  
M. E. Koepke ◽  
D. J. Knudsen
Keyword(s):  
Fluid Model ◽  
Collisionless Plasma ◽  
Alfven Wave ◽  
Temperature Anisotropy ◽  
Thermal Pressure ◽  
Exclusion Region ◽  
Two Fluid Model ◽  
The Magnetic Field ◽  
Range Of Values ◽  
Two Fluid

Abstract. The stationary inertial Alfvén (StIA) wave (Knudsen, 1996) was predicted for cold, collisionless plasma. The model was generalized (Finnegan et al., 2008) to include nonzero values of electron and ion collisional resistivity and thermal pressure. Here, the two-fluid model is further generalized to include anisotropic thermal pressure. A bounded range of values of parallel electron drift velocity is found that excludes periodic stationary Alfvén wave solutions. This exclusion region depends on the value of the local Alfvén speed VA, plasma beta perpendicular to the magnetic field β⊥ and electron temperature anisotropy.

scholarly journals Does the Magnetodynamic Model for the Formation of AGN Jets Survive New Findings of High-energy Phenomena near the Central Objects?

2000 ◽  
Vol 195 ◽  
pp. 473-481
Author(s):  
Y. Uchida
Keyword(s):  
Lorentz Factor ◽  
High Energy ◽  
Major Effect ◽  
Alfven Wave ◽  
Poynting Flux ◽  
Central Engine ◽  
New Findings ◽  
Wave Trains ◽  
Kink Instability ◽  
Jet Structure

Here, we argue that, despite all-new findings of phenomena with very large Lorentz factors, the importance of the magnetodynamic process accelerating and collimating AGN jets should not be affected because there exists evidence in the features of the jets and tails at large distances indicating that the wiggles of the jet structure are likely to be due to a magnetic, helical kink instability. These systematic features require too much energy and coherence of the driving process to be produced locally and axe most naturally produced by a magnetic effect coming from the powerful central engine. This indicates that the major effect producing the jets, and the lobes with hotspots at the tips of the jets, is likely to be the Poynting flux carried by torsional Alfvén wave trains plus the re-accelerated high-energy particles in them. The very large Lorentz-factor phenomena should not hinder the transfer of these magnetic effects and are likely to be byproducts of the basic magnetodynamic process, and not the reverse.

Nonlinear decay of a propagating lower-hybrid wave in a plasma

1978 ◽  
Vol 19 (1) ◽  
pp. 87-96 ◽  
Author(s):  
P. K. Shukla ◽  
M. A. Mamedow
Keyword(s):  
Electromagnetic Waves ◽  
Fluid Model ◽  
Wave Interaction ◽  
Alfven Wave ◽  
Lower Hybrid ◽  
Threshold Condition ◽  
Hybrid Wave ◽  
Lower Hybrid Wave ◽  
Two Fluid Model ◽  
Two Fluid

This paper studies the nonlinear coupling between a large amplitude propagating lower-hybrid wave and two electromagnetic waves in a plasma. Using a two-fluid model and Vlasov and Maxwell's equations, we derive a dispersion relation governing this three-wave interaction process. It is shown that a finite wavenumber lower-hybrid pump can decay into a whistler and a kinetic Alfvén wave. Calculations of the threshold condition suggest that this decay process may occur both in the laboratory and in the ionosphere.

scholarly journals ULTRA-LOW INTENSITY PROTON BEAMS FOR RADIATION RESPONSE RELATED EXPERIMENTS AT THE U-120M CYCLOTRON

2018 ◽  
Vol 14 ◽  
pp. 21
Author(s):  
Tomas Matlocha ◽  
Filip Krizek
Keyword(s):  
Proton Beam ◽  
Nuclear Physics ◽  
High Energy Physics ◽  
Tracking System ◽  
Operation Mode ◽  
High Energy ◽  
Ion Source ◽  
Alice Experiment ◽  
Physics Institute ◽  
Academy Of Sciences

The U-120M cyclotron at the Nuclear Physics Institute (NPI) of the Czech Academy of Sciences in Rez is used for radiation hardness tests of electronics for high-energy physics experiments. These tests are usually carried out with proton fluxes of the order of 10<sup>5</sup>–10<sup>9</sup> proton·cm<sup>−2</sup>·s<sup>−1</sup>. Some tests done for the upgrade of the Inner Tracking System of the ALICE experiment at CERN, however, required proton beam intensities several orders of magnitude lower. This paper presents a method which has been developed to achieve the proton beam flux of the order of 1 proton · cm<sup>−2</sup>·s<sup>−1</sup>. The method is mainly based on reduction of the discharge current in the cyclotron internal Penning type ion source. Influence of this new operation mode on the lifetime of ion source cathodes is discussed.

scholarly journals Nontraumatic Spondylolisthesis of the Axis with Cervical Kyphosis

2020 ◽  
Vol 2020 ◽  
pp. 1-3
Author(s):  
Shuhei Mizobuchi ◽  
Nobuaki Tadokoro ◽  
Shogo Takaya ◽  
Katsuhito Kiyasu ◽  
Ryuichi Takemasa ◽  
...  
Keyword(s):  
Facet Joint ◽  
Relevant Literature ◽  
Plain Radiograph ◽  
High Energy ◽  
Cord Compression ◽  
Facet Joints ◽  
Cervical Kyphosis ◽  
Posterior Decompression ◽  
Traumatic Episode ◽  
Possible Cause

This study aimed at presenting a rare nontraumatic spondylolisthesis of the axis and considering its possible cause. Traumatic spondylolisthesis of the axis, called hangman’s fracture, frequently occurs as a high-energy trauma. However, nontraumatic spondylolisthesis of the axis is quite rare, and relevant literature on this condition is scarce. We reported a case of a 49-year-old man who had spondylolisthesis of the axis without experiencing a traumatic episode. Plain radiograph and CT image showed 7.0 mm anterolisthesis of the axis. Both C2 and C3 facet joints positioned asymmetrically, and the unilateral side oriented coronally, which was less resistant to rotational motion. These facet joint abnormalities could cause segmental instability and spondylolisthesis of the axis. Due to the resultant myelopathy, the slip with cord compression was surgically corrected by posterior decompression with instrumented fusion.

Investigation of a Passive DMFC Mini-Stack at Room Temperature

2010 ◽  
Vol 72 ◽  
pp. 271-276 ◽  
Author(s):  
Antonino Salvatore Arico’ ◽  
Vincenzo Baglio ◽  
Alessandro Stassi ◽  
Vincenzo Antonucci
Keyword(s):  
Direct Methanol Fuel Cells ◽  
Operation Mode ◽  
High Energy ◽  
High Energy Density ◽  
Catalyst Loading ◽  
Ambient Conditions ◽  
Electrode Thickness ◽  
Power Sources ◽  
Catalytic Sites ◽  
Direct Methanol

Direct Methanol Fuel Cells (DMFCs) are promising candidates for portable electric power sources because of their high energy density, lightweight, compactness, simplicity as well as easy and fast recharging. Recently, the attention has been focused on portable applications with passive-feed DMFCs. Under this configuration, DMFCs operate without any external device for feeding methanol and blowing air into the cells. An investigation of properties and operating parameters of a passive DMFC monopolar mini-stack, such as catalyst loading and methanol concentration, was carried out. From this analysis, it was derived that a proper Pt loading is necessary to achieve the best compromise between electrode thickness and number of catalytic sites for the anode and cathode reactions to occurs at suitable rates. Methanol concentrations ranging from 1 M up to 10 M (40 vol%) and an air-breathing operation mode were investigated. A maximum power of 225 mW was obtained at ambient conditions for a three-cell stack, with an active single cell area of 4 cm2 corresponding to a power density of about 20 mW cm-2.

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