First EMC3‐EIRENE Simulations with Divertor Legs of LHD in Realistic Device Geometry

Plasma and Fusion Research

Miyazawa

Goto

et al. 2018

Recently, a new limiter concept with liquid metal for a helical fusion reactor was proposed. This work present a modeling study to understand the influence of the limiter to the plasma and to find critical parameters for the liquid limiter concept. EMC3-EIRENE code is applied to a limiter configuration of a vertical column formed with plane surfaces at the inboard side of the Large Helical Device (LHD). The calculation results indicate that heat load on the helical divertor plates is significantly reduced when the limiter is inserted into the ergodic layer even without impurities. However, the influence of impurity radiation is too large in some cases. In order to achieve a large reduction of divertor flux and to avoid a large reduction of core electron temperature, parameter scans with limiter position and sputtering yield were performed. The results suggest that the limiter position is a critical parameter for acceptable degradation of the core and sufficient reduction of divertor flux.

Section: Modeling Of a Liquid Metal Limitermentioning

confidence: 99%

Application of EMC3-EIRENE to Estimation of Influence of a Liquid Metal Limiter on an LHD-Type Fusion Plasma

Plasma and Fusion Research

Miyazawa

Goto

et al. 2018

“…A three‐dimensional model for the impurity transport simulation for R ax = 3.60 m is shown in Figure . The model includes the peripheral plasma (ergodic layer), the divertor legs, the vacuum vessel, the helical coil cans, and the divertor components for one‐half of the helical coil pitch angle (18° in toroidal direction) . The typical width of the grid cells in the model is less than 10 mm, but it depends on the radial and poloidal positions of the cells.…”

Section: Set‐up Of Impurity Transport Simulation In the Lhd Peripheramentioning

confidence: 99%

Investigation of dust shielding effect of intrinsic ergodic magnetic field line structures in the peripheral plasma in the large helical device

Shoji

Contributions to Plasma Physics

Smirnov

et al. 2018

Self Cite

Recent long pulse discharges in the large helical device (LHD) have been interrupted by radiation collapse induced by the emission of dust from the surface of the vacuum vessel and the divertor region. The dust shielding effect by intrinsic ergodic magnetic field line structures (ergodic layer) formed around the main plasma confinement region is investigated using a three‐dimensional peripheral plasma fluid code (EMC3‐EIRENE) coupled with a dust transport simulation code (DUSTT). Simulations performed in three different magnetic configurations with narrow, medium, and wide ergodic layers show that the wide ergodic layer is not always effective in shielding the main plasma from the dust emission. Optimum operational regimes for controlling the influence of the dust emission on the sustainment of plasma discharges are found by investigating the impurity ion content in the peripheral plasma for various plasma heating powers and plasma densities in the three magnetic configurations.

“…The transport of carbon atoms and ions in the peripheral plasma in fully three-dimensional geometry has been investigated using the EMC3-EIRENE [6][7][8]. Figure 3 shows a three-dimensional grid model for the simulation, including the divertor components and the vacuum vessel for a half of one helical pitch (18 • in toroidal angle).…”

Section: Set Up For the Simulation Of The Density Profile Of Carbon Dmentioning

confidence: 99%

Simulation Analysis of Carbon Deposition Profile in the Closed Helical Divertor Configuration in the Large Helical Device

Shoji

Tanaka

et al. 2016

Contrib. Plasma Phys.

Self Cite

Recent long pulse plasma discharges in the Large Helical Device have been interrupted by radiation collapse induced by large amounts of dusts released from a closed divertor region. Traces of exfoliation of carbon-rich mixed material deposition layers were found in the divertor region after the experimental campaigns, indicating that the thickly accumulated deposited layers were exfoliated and broken into dusts. Simulation of the density profiles of carbon deposition in the divertor region by EMC3-EIRENE reasonably explains the observation of the exfoliation of the deposition layers. It shows that the positions of the exfoliated layers correspond to the area where the density of the carbon deposition is high. It also proves that change of the configuration of target plates in the closed divertor is effective for controlling the accumulation of the carbon deposition, and carbon atoms released from the new target plates does not influence the main plasma confinement region.