Nickel migration during high-field side (HFS) and low-field side (LFS) limiter phases in the JET ITER-Like wall (JET-ILW) is studied using the 3D impurity Monte Carlo code ERO2.0, executed on plasma backgrounds created by SOLPS-ITER. The HFS and LFS limited SOLPS-ITER simulations are adjusted to represent limiter plasmas during plasma startup and termination in the 2011–2016 JET-ILW campaigns.The atomic fluxes to the vacuum vessel are predicted by EIRENE. Additionally, the energy spectra of the atomic flux are obtained from a set of diagnostic surfaces added to the EIRENE simulation. The EIRENE-predicted energy spectra are comprised of a population of low energy (<5 eV) atoms from molecular dissociation and a population of higher energy atoms created through charge exchange (CX). The CX atoms approximately follow a Maxwell–Boltzmann distribution, with a fit temperature equal to Ti,sep.ERO2.0 predicts nickel to erode primarily from the vacuum vessel wall on the LFS midplane at a gross rate of 1.4×1020 s−1 in the HFS limited configuration and at a gross rate of 5.0×1020 s−1 in the LFS limited configuration. Nickel is predicted to ionize in the scrape-off layer and be transported by plasma flows towards the contact point between plasma and wall where it deposits. Nickel deposition onto the divertor tiles is predicted to occur through ballistic trajectories from the source at the vacuum vessel wall.
Understanding impurity redeposition in plasma–wall transition regions is essential for predicting the lifetime and performance of plasma-facing components in fusion devices. In this work, the sheath-driven redeposition of sputtered lithium, tin, and tungsten is investigated using a Monte Carlo code coupled to electrostatic potential profiles obtained from Particle-in-Cell simulations. The study examines the influence of magnetic field inclination to the wall, plasma conditions, ionization processes, and incoming ion species on redeposition dynamics. In the context of an academic study, the sheath electric field is suppressed, and three redeposition regimes are identified depending on the relative magnitudes of the ionization mean free path, plasma–wall transition extent, and impurity gyroradii. A theoretical expression for long-range redeposition is derived and shown to accurately reproduce simulation results when gyromotion effects remain weak. The inclusion of self-consistent sheath electric fields significantly enhances redeposition and reduces its dependence on magnetic inclination. Heavy impurities such as Sn and W exhibit high redeposition fractions in compact-like scenarios because their shorter ionization mean free paths lead to ionization in regions of strong electric field, whereas Li is more easily ionized outside the sheath region. The influence of projectile mass and charge state is also analyzed through binary collision theory. These results highlight the dominant role of sheath electric fields and ionization physics in determining impurity redeposition near plasma-facing surfaces.
An integrated workflow for modeling fast-flow, open-surface liquid lithium divertors under fusion pilot plant conditions has been developed as part of the ongoing SciDAC-5 project on Simulation of Plasma–Liquid Metal Interactions. The workflow couples SOLPS-ITER and OpenEdge and is applied here to the Compact Advanced Tokamak (CAT) divertor geometry. SOLPS-ITER provides the boundary plasma solution, plasma-facing-component heat and particle fluxes, and background plasma conditions, while OpenEdge is used to compute lithium release, transport, ionization, and associated particle and energy source terms arising from evaporation, physical sputtering, ad-atom sputtering, and parameterized droplet emission. A reduced liquid-metal magnetohydrodynamic and heat-transfer model is used to estimate the lithium surface temperature and evaporation rate for different inlet flow speeds. Compared with previous liquid-metal divertor modeling workflows, the present approach includes a more self-consistent OpenEdge treatment of lithium sputtering using local sheath-accelerated ion energies and incidence angles, and incorporates droplet tracking to assess the importance of mist, droplet, and ligament source regimes. For the CAT conditions considered here, the continuous lithium source from evaporation, physical sputtering, and ad-atom emission is strongly reduced by partial detachment achieved by neon seeding, decreasing by a factor of ≈50 from 6.3×1023 atoms per second in the attached case to 1.3×1022 atoms per second in the partially detached case. OpenEdge droplet-trajectory calculations show that the droplet generation rate required to equal the continuous wall source depends strongly on the characteristic droplet size: approximately 109–1010s−1 for micron-scale mist, 106–107s−1 for 100-micrometer-scale droplets, and 103–104s−1 for millimeter-scale ligaments. These results indicate that rare large ligaments can contribute lithium sources comparable to continuous sputtering and evaporation, while fine mist requires much larger number fluxes to have a similar effect. Two-way coupled SOLPS-ITER and OpenEdge simulations, in which the lithium source is iterated with the plasma background, demonstrate progress towards integrated plasma–liquid-metal modeling within the SciDAC-5 framework and provide a basis for future optimization of lithium flow conditions, divertor geometry, impurity seeding, and self-consistent droplet-generation models.
Liquid metal solutions are considered as plasma facing materials for future fusion power plants. It is important to characterize their ability for heat and particle exhaust as well as their impact on the plasma. Several concepts are proposed such as free flowing lithium layers or lithium in capillary porous system. To assess their performances, transport simulations are performed with SOLEDGE3X-EIRENE. A wall model is implemented to simulate the response of the liquid wall to the incident plasma load, including a thermal model and a model for lithium evaporation and erosion. The wall model is dynamically coupled to SOLEDGE3X to simulate the transport of lithium in the plasma and compare the different liquid lithium concepts. A hypothetical application to the WEST tokamak is proposed to illustrate the coupling.
Boronization is routinely applied in fusion devices to reduce oxygen (O) impurity influx, to improve wall conditioning, and to control fuel recycling by forming boron (B)-containing layers on plasma-facing components (PFCs). In the non-axisymmetric geometry of Wendelstein 7-X (W7-X), however, the spatial distribution of B during glow-discharge (GD) boronization in B 2 H 6 -helium (He)-mixture is expected to be strongly affected by the three-dimensional arrangement of anodes, gas-injection locations and local discharge conditions. In this work, five toroidally distributed GD anodes (DCB) retrieved from W7-X after the OP2.1 campaign were investigated by ex-situ picosecond laser-induced breakdown spectroscopy (ps-LIBS). Pulse-resolved LIBS measurements were used to identify B-containing deposits and to derive depth-dependent information, while focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray spectroscopy (EDS) analyses on a DCB30 specimen provided complementary morphological, thickness, and compositional information. Clear emission signals from B, hydrogen (H), O and the graphite substrate C were obtained by the laser-induced plasma, allowing the deposited layer and substrate contribution to be distinguished as a function of laser pulse number. The intensity ratio of B/C revealed pronounced spatial non-uniformity on individual anodes, including both radial and circumferential asymmetry. After calibration of the effective ablation rate using crater profilometry and FIB-SEM cross sections, the local estimated B-containing deposit thickness ranged from 539 nm on DCB10 in sector 1 to 1782 nm on DCB30 in sector 3, far exceeding the hypothetical uniform coverage thickness of 130 nm in the vessel, which is used here only as a reference scale rather than as an expected deposition thickness for the positively biased anodes. The overall deposition level followed the trend DCB30 > DCB21 > DCB11 > DCB40 > DCB10. FIB-SEM observations showed that the deposits were strongly attached to the fine-grain graphite substrate, without evidence of loosely bound flakes in the investigated regions. These results provide spatially resolved experimental data for assessing B deposition and redistribution after W7-X boronization and offer benchmarks for future modeling of boronizations as well as input to the source distribution in simulations of B transport in three-dimensional magnetic confinement devices.
