• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3724-3731
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• 2022

It is important for an ICRF full wave code to simulate the SOL (Scrape Off Layer) plasma as well as the core inside of the LCFS (Last Closed Flux Surface) for the precise prediction of the coupling between the antenna and the core plasma in tokamaks. To this end, a two dimensional full wave code based on a Fourier spectral algorithm has been developed. The spectral algorithm and procedures are described and the simulation results for the minority heating in KSTAR are reported including electric field, power absorption and power flux.

• Nuclear Engineering and Technology
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• 제30권1호
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• pp.17-25
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• 1998

Transport of carbon and boron impurity ions parallel to magnetic field lines in the tokamak SOL (scrape-off layer) is numerically investigated for a one-dimensional steady state. The spatial distributions of density and velocity of the impurity ions in a steady state are calculated by finite difference method for a single-fluid model. The calculated results show that among forces acting on SOL particles thermal force produced tv plasma temperature gradient is a principal force determining the feature of impurity distribution profiles in the tokamak edge. However, strong collisional friction forces appearing dominant in front of the diverter plate restrain impurity ion flows due to temperature gradients from moving toward the midplane. Consequently, the stagnation point develops in the impurity flow by these two forces near the diverter region, in which ion flows change their directions. Impurity ions turn out to be accumulated at the stagnation points, where peaked profiles of highly-ionized state ions are relatively predominant over those of low-ionized state ions.

• Nuclear Engineering and Technology
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• 제56권11호
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• pp.4620-4627
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• 2024

We introduce a novel fast-reciprocating probe head installed on the EAST (Experiment Advanced Superconducting Tokamak) containing 12 graphite tips. This allows us to measure a variety of plasma parameters such as the plasma density, temperature, and space potential in the scrape-off layer (SOL). We will also acquire the data at high frequency thus measuring the ion saturation current, I_sat, and the floating potential, V_f, average and fluctuating values. Moreover, with poloidally separated tips, we measure the poloidal electric field, E_θ, at two toroidal locations, assuming a plasma flow dominated by the E×B drift this leads to the determination of the radial velocity. As a consequence, the turbulent radial flux will thus be determined. In the parallel direction, we have four tips that are aligned parallel with the magnetic field lines, thus making an angle of 4°24' to the horizontal direction. This unique design should allow the measurement of the toroidal wavenumber, k_φ, a quantity rarely obtained in tokamaks. This new probe, with 7 tips for measuring the ion saturation current and 4 tips to measure the floating potentials, was used on the EAST during the 2023 summer campaign. We present the first experimental results obtained during an L-mode plasma.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.207-219
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• 2022

The suppression of high-intensity blob structures in the scrape-off layer (SOL) by ion-cyclotron range of frequencies (ICRF) power, leading to a decrease in the turbulent fluctuation level, is observed first in the Experimental Advanced Superconducting Tokamak (EAST) experiment. This suppression effect from ICRF power injection is global in the whole SOL at EAST, i.e. blob structures both in the regions that are magnetically connected to the active ICRF launcher and in the regions that are not connected to the active ICRF launcher could be suppressed by ICRF power. However, more ICRF power is required to reach the full blob structure suppression effect in the regions that are magnetically unconnected to the active launcher than in the regions that are magnetically connected to the active launcher. Studies show that a possible reason for the blob suppression could be the enhanced E_r × B shear flow in the SOL, which is supported by the shaper radial gradient in the floating potential profiles sensed by the divertor probe arrays with increasing ICRF power. The local RF wave power unabsorbed by the core plasma is responsible for the modification of potential profiles in the SOL regions.

• Nuclear Engineering and Technology
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• 제54권10호
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• pp.3717-3723
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• 2022

For the first time, two-dimensional temporal behavior of the edge localized mode (ELM) filament is measured in the edge tokamak plasma with a multi-channel electrical probe array (MCEP). MCEP, which has 16 floating probes (4 × 4), is mounted at the far scrape-off layer (SOL) region in the KSTAR. An electron temperature and an ion flux are measured by sideband method (SBM), which can achieve two-dimensional measurements with high time resolution. Furthermore, temporal evolutions of the electron temperature and the ion flux are obtained during the ELM occurrence. In the H-mode period, short spikes from ELM bursts are observed in measured plasma parameters, and the trend is similar to that of typical Hα signal. Interestingly, when blob-like ELM filaments crash the probe, the heat flux is significantly higher in a local region of the probe array. The results show that our probe array using the SBM can measure the ELM behavior and the plasma parameters without the effect of the stray current caused by the huge device. This study can provide valuable data needed to understand the interaction between the SOL plasma and the plasma facing components (PFCs).