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This work describes integrated numerical modelling applied to DEMO discharges with tungsten wall and divertor, using the COREDIV code, which self-consistently solves 1D radial transport equations of plasma and impurities in the core region and 2D multi-fluid transport in the SOL. The model is self-consistent with respect to both the effects of impurities on the α-power level and the interaction between seeded (Ar) and intrinsic impurities (tungsten, helium). This work is to analyse the influence of the helium and hydrogen recycling on the He confinement time in DEMO reactor. Simulations have been done for argon seeding puff 5.0 × 10211/s. It is found that recycling coefficient of helium have strong influence on the He confinement time, which increases from 7.25 s to 26.9 s going from lowest to highest recycling coefficient, but it has small influence on the effective charge state and radiation in the SOL. Alpha power decreases only by about 20%, which is the effect of main plasma dilution. [ABSTRACT FROM AUTHOR]

Highlights • The COREDIV code has been used to simulate DEMO inductive discharges with different impurity seeding (Ar, Xe) and mix gasses. • For xenon seeding for case with standard radial diffusion in SOL, such regime of operation seems not to be possible. • For Ar and combined Ar+Xe seeding it is possible to achieve H-mode plasma operation with acceptable level of the power to the target, but is upper limit on Xe concentration. • The influence of the prompt re-deposition model on the DEMO working point is relatively weak. Abstract In this paper numerical simulations with COREDIV code, which self-consistently solves radial transport equations in the core region and 2D multi-fluid transport in the SOL of EU DEMO discharges in full tungsten environment (W divertor and wall) for H-mode scenario has been performed with different impurity seeding. The optimal impurity mix for reactor would require the use of high Z impurity (low dilution, higher P α) in core and low/medium Z impurity radiating in the SOL region. In this paper we focus on investigations how the operational domain of EU DEMO can be influenced by different seeding (Ar, Xe) and mix gasses. In case of Xenon seeding, H-mode operation can NOT be achieved for standard radial diffusion (D SOL = 0.5m2/s) in the SOL. In the simulation, we have considered combined seeding of Ar (good radiator in SOL) and Xe (good radiator in core). In order to find the optimal impurity mix, simulations have been performed in such a way that for a few fixed levels of Xe puff, Ar puff has been increased from zero to the maximum value allowed by the code stability. For combined seeding: xenon + argon working point for EU DEMO can be found. [ABSTRACT FROM AUTHOR]

Abstract The long-term operations of the EAST experiments result in a substantial redeposition of impurities on the first wall, which is considered as the potential impurity source during the discharge. The transport properties of lithium impurity in the scrape-off layer (SOL) of EAST have been studied by the three-dimensional (3D) edge transport code, the EMC3-EIRENE. The neutral lithium impurities from four impurity source positions on the first wall have been used in the modelling. The detailed analysis of the relationship between the impurity source positions and the density profiles of the lithium impurity for different charge states has been carried out. It is found that the density profiles of the Li1+ ions are determined by the impurity source positions, whereas the density profiles of the Li2+ and Li3+ ions are not related to the first wall source positions. [ABSTRACT FROM AUTHOR]

A two dimension-in-space and three dimension-in-velocity (2d3v) Particle-In-Cell (PIC) code is applied to investigate the plasma behaviors at the divertor gaps region in this work. Electron and D + ion fluxes to the tile surface in the poloidal and toroidal gaps for different shaped edges are compared to demonstrate the optimized tile geometry. For poloidal gap, shaped edge in the shadowing side makes more ions penetrate into the gap, while shaped edge in the wetted side can mitigate the peak flux value. For toroidal gap, most ions entering the gap impinge on the side tile mainly due to the E × B drift, and shaped wetted edges also can mitigate the peak heat fluxes. In addition, effects of magnetic field inclination angle from toroidal direction on the plasma behaviors are simulated for poloidal and toroidal gaps, respectively. It is found that the magnetic field angles don’t influence the plasma behaviors in poloidal gap; while significant changes have been observed in the toroidal gap. [ABSTRACT FROM AUTHOR]

ITER expects to produce fusion power of about 0.5GW when operating with tungsten (W) divertor and beryllium (Be) wall. The influx of W from divertor can have significant influence on the discharge performance. This work describes predictive integrated numerical modeling of ITER discharges using the COREDIV code, which self-consistently solves the 1D radial energy and particle transport in the core region and 2D multi-fluid transport in the SOL. Calculations are performed for inductive ITER scenarios with intrinsic (W, Be and He) impurities and with seeded impurities (Ne and Ar) for different particle and heat transport in the core and different radial transport in the SOL. Simulations show, that only for sufficiently high radial diffusion (both in the core and in the SOL regions), it is possible to achieve H-mode mode plasma operation (power to SOL > L-H threshold power) with acceptable low level of power reaching the divertor plates. For argon seeding, the operational window is much smaller than for neon case due to enhanced core radiation (in comparison to Ne). Particle transport in the core characterized by the ratio of particle diffusion to thermal conductivity) has strong influence on the predicted ITER performance. [ABSTRACT FROM AUTHOR]

Numerical simulation with COREDIV code of DEMO H-mode discharges (tungsten divertor and wall) are performed considering the influence of seeding impurities with different atomic numbers: Ne, Ar and Kr on the DEMO scenarios. The approach is based on integrated numerical modeling using the COREDIV code, which self-consistently solves radial transport equations in the core region and 2D multi-fluid transport in the SOL. In this paper we focus on investigations how the operational domain of DEMO can be influenced by seeding gasses. Simulations with the updated prompt re-deposition model implemented in the code show that only for Ar and Kr, for high enough radial diffusion in the SOL, it is possible to achieve H-mode plasma operation (power to the SOL> L-H transition threshold power) with acceptable level of the power to the target plates. For neon seeding such regime of operation seems not to be possible. [ABSTRACT FROM AUTHOR]

Abstract: The thermal behavior of a directly water-cooled W/Cu movable poloidal limiter was investigated in HT-7, a medium-sized superconducting tokamak with limiter configuration, major radius R =1.22m, and minor radius a =0.27m. The W/Cu movable limiter (ML) was exposed to the plasma at various radial positions at r < a. The surface and bulk temperatures were monitored by an IR-camera and the thermocouples, respectively. The heat flux deposited on the limiter was evaluated by an ANSYS code using the measured surface temperatures as boundary conditions. It was found that the maximum heat flux incident on the ML was less than 1MW/m2 in the Ohmic discharges, but reached up to 5–7MW/m2 in the discharges with lower hybrid current drive (LHCD). A simple model was developed to understand heat transport to the W/Cu ML, taking into account the “funnel effect”. [Copyright &y& Elsevier]