Search results for " PLASMA"

Understanding tungsten erosion during inter/intra-ELM periods in He-dominated JET-ILW plasmas

2021

Tungsten erosion was quantified during inter/intra-ELM periods in He-dominated JET-ILW plasmas by optical emission spectroscopy. The intra-ELM tungsten sputtering in helium plasmas, which dominates the total W source, prevails by a factor of about 4 over inter-ELM sputtering in the investigated ELM frequency range from 90 Hz-120 Hz. He ions are mainly responsible for the W erosion during the ELMs in He plasmas. The strong in/out asymmetry of the ELM-induced W erosion is observed in He plasmas even at high ELM frequencies beyond 100 Hz. In Ohmic/L-mode plasmas and during the H-mode inter-ELM plasma phases both He2+ and Be2+ ionic species are major contributors to the W erosion. Their contrib…

Erosion, screening, and migration of tungsten in the JET divertor

2019

The erosion of tungsten (W), induced by the bombardment of plasma and impurity particles, determines the lifetime of plasma-facing components as well as impacting on plasma performance by the influx of W into the confined region. The screening of W by the divertor and the transport of W in the plasma determines largely the W content in the plasma core, but the W source strength itself has a vital impact on this process. The JET tokamak experiment provides access to a large set of W erosion-determining parameters and permits a detailed description of the W source in the divertor closest to the ITER one: (i) effective sputtering yields and fluxes as function of impact energy of intrinsic (Be,…

Strictly correlated electrons approach to excitation energies of dissociating molecules

2019

In this work we consider a numerically solvable model of a two-electron diatomic molecule to study a recently proposed approximation based on the density functional theory of so-called strictly correlated electrons (SCE). We map out the full two-particle wave function for a wide range of bond distances and interaction strengths and obtain analytic results for the two-particle states and eigenenergies in various limits of strong and weak interactions, and in the limit of large bond distance. We then study the so-called Hartree-exchange-correlation (Hxc) kernel of time-dependent density functional theory which is a key ingredient in calculating excitation energies. We study an approximation b…

VUV-diagnostics of low temperature hydrogen plasmas

2015

Hydrogen plasma induced photoelectron emission from metal surfaces

2018

Low temperature hydrogen plasmas are strong sources of vacuum ultraviolet radiation. The properties of laboratory plasmas can be influenced by surface processes induced by photons with their energies exceeding the surface work function of the wall material. In this work, the plasma induced photoelectron emission has been studied with different ion sources. The emission depends on the mechanical design of the plasma device, plasma heating method and the discharge power (density). Parametric studies include the quantifying of the emission from different metal surfaces, commonly used as plasma facing materials in ion sources, as well as alkali metal covered surfaces. Experimental studies sugges…

Vertex corrections for positive-definite spectral functions of simple metals

2016

We present a systematic study of vertex corrections in the homogeneous electron gas at metallic densities. The vertex diagrams are built using a recently proposed positive-definite diagrammatic expansion for the spectral function. The vertex function not only provides corrections to the well known plasmon and particle-hole scatterings, but also gives rise to new physical processes such as generation of two plasmon excitations or the decay of the one-particle state into a two-particles-one-hole state. By an efficient Monte Carlo momentum integration we are able to show that the additional scattering channels are responsible for the bandwidth reduction observed in photoemission experiments on…

High-Reynolds-number turbulent cavity flow using the lattice Boltzmann method

2018

We present a boundary condition scheme for the lattice Boltzmann method that has significantly improved stability for modeling turbulent flows while maintaining excellent parallel scalability. Simulations of a three-dimensional lid-driven cavity flow are found to be stable up to the unprecedented Reynolds number $\mathrm{Re}=5\ifmmode\times\else\texttimes\fi{}{10}^{4}$ for this setup. Excellent agreement with energy balance equations, computational and experimental results are shown. We quantify rises in the production of turbulence and turbulent drag, and determine peak locations of turbulent production.

Designing a graphics processing unit accelerated petaflop capable lattice Boltzmann solver: Read aligned data layouts and asynchronous communication

2016

The lattice Boltzmann method is a well-established numerical approach for complex fluid flow simulations. Recently, general-purpose graphics processing units (GPUs) have become available as high-performance computing resources at large scale. We report on designing and implementing a lattice Boltzmann solver for multi-GPU systems that achieves 1.79 PFLOPS performance on 16,384 GPUs. To achieve this performance, we introduce a GPU compatible version of the so-called bundle data layout and eliminate the halo sites in order to improve data access alignment. Furthermore, we make use of the possibility to overlap data transfer between the host central processing unit and the device GPU with com…

Measurement of dielectron production in central Pb-Pb collisions at √sNN = 2.76 TeV

2019

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. The first measurement of dielectron (e + e −) production in central (0 – 10 %) Pb – Pb collisions at √sNN=2.76TeV at the LHC is presented. The dielectron invariant-mass spectrum is compared to the expected contributions from hadron decays in the invariant-mass range 0 < mee < 3.5 GeV / c2. The ratio of data and the cocktail of hadronic contributions without vacuum ρ0 is measured in the invariant-mass range 0.15 < mee < 0.7 GeV / c2, w…

Regulación del volumen plasmático en el ejercicio: papel de la intensidad y la adaptación al entrenamiento.

2016

La función del sistema circulatorio es la de mantener el entorno celular apropiado para el correcto desarrollo y supervivencia de los tejidos, aportando nutrientes, O2, y hormonas, al mismo tiempo que se retiran productos de desecho y CO2 (Guyton and Hall 2006b). Por tanto, el sistema circulatorio juega un papel fundamental en el mantenimiento de la homeostasis (Cannon 1929). Para cumplir esta misión, es fundamental mantener el flujo sanguíneo en todos los tejidos del organismo en función de las necesidades. El sistema circulatorio regula el flujo sanguíneo en todo el cuerpo mediante diversos mecanismos de feedback que modulan el gasto cardíaco (Q), la presión sanguínea y la distribución lo…