Simulations on W impurity transport in the edge of EAST H-mode plasmas

Tungsten (W) transport and screening in the edge plasma are investigated for EAST high dissipative divertor conditions. By combining the one-dimensional impurity fluid model (1DImpFM) and the two-point model formatting (2PMF), W screening is proved to be enhanced for high upstream plasma density conditions, mainly because the impurity temperature gradient velocity decreases with the increase of the upstream plasma density. Based on dedicated EAST density ramp-up experiments, two-dimensional simulations of W erosion and transport are carried out for different levels of dissipative divertor conditions by using the SOLPS-DIVIMP code package, and the modeling results are benchmarked with the 1DImpFM analytic model. The prompt-redeposition, the divertor screening, and the main SOL screening are quantitatively analyzed. For detached divertor conditions, the increase of the W ionization length reduces the prompt redeposition rate, but both the divertor screening and SOL screening are reinforced. The 1DImpFM can well interpret the W leakage in the near separatrix region; however, the 2D simulations suggest that the impurity pressure gradient force which is neglected by the 1DImpFM plays an important role, especially in the far-SOL region. With the divertor condition varied from the high-recycling regime to the deep detachment regime, the W source moves from the near strike point region to the far SOL, and thus makes the W transport in the far SOL more important. Therefore, the impurity pressure gradient force cannot be neglected for edge W transport analysis, especially for the detached divertor conditions.

Section: The Background Plasma and The Simulation Setupmentioning

confidence: 99%

Modelling of tungsten impurity edge transport and screening for different divertor conditions in EAST

Wang

Xu²,

Ding³

et al. 2022

“…DIVIMP is a two-dimensional (2D) impurity transport code that uses the Monte-Carlo method [72,73] and is widely applied for modeling the impurity transport in the plasma edge owing to its simple structure, short calculation time, and applicability in plasma of any collisionality [19,23,27]. In this work, DIVIMP is employed to simulate the transport of W, which is treated as a trace impurity in the plasma background provided by SOLPS-ITER simulation.…”

Section: Simulation Schemementioning

confidence: 99%

“…Therefore, it is of great importance to understand the transport of W impurities in the scrape-off layer (SOL), which determines the source of the tungsten contamination inside the confined plasma. Many efforts have been conducted on this subject for various existing tokamaks, such as EAST [19][20][21][22], DIII-D [23,24], JET [25][26][27], and ASDEX-Upgrade [28], and for future fusion reactors, such as ITER [29,30], CFETR [31][32][33], and DEMO [34].…”

Section: Introductionmentioning

confidence: 99%

Simulation study of the influence of E× B drift on tungsten impurity transport in the scrape-off layer

Guo,

Xu,

Mao

et al. 2023

Future fusion reactors such as ITER have adopted tungsten (W) as the plasma-facing materials (PFMs) in the divertor region. It is crucial to keep the W concentration in the core plasma at an extremely low level. Great efforts have been put forward on understanding the W transport in the scrape-off layer (SOL), which is related to the source of the core W contamination. In this work, the influence of E×B drift on the W impurity transport in the SOL is studied by numerical simulations for a model case based on EAST upper single-null configuration with high recycling divertor plasma. The W transport is simulated using DIVIMP on the background plasma obtained from SOLPS-ITER simulation including drifts. The E×B drift of the W ions is introduced according to the background electric field. Therefore, both the direct E×B drift effect of W ion itself and the indirect effect via background plasma on the W transport process in the SOL can be studied. We focus on the influence on the flux of W impurities entering confined plasma across the last closed flux surface Γenter, which is expected to be proportional to the core W concentration. It is found that Γenter is mainly from the outer (inner) target under favorable (unfavorable) toroidal field BT, and can be increased by more than one order of magnitude compared with the case without drifts. It reflects the significant influence of E×B drift effects. The detailed effects due to the background plasma and the poloidal and radial E×B drift of W ion, as well as the related mechanisms, are analyzed for the three stages of W transport in the SOL, including the effective sputtering from the target, the leakage from the divertor and the entry into the confined plasma.

“…It is important to ensure that the rate of ionization is not too high to prohibit sufficient beam penetration, nor too low to allow a significant portion of the beam to pass straight through the plasma [16]. Therefore, the common plasma impurities like carbon, nitrogen, and oxygen are of special interest as well as metallic species sputtered from the container walls [17][18][19]. So, the accurate knowledge of various cross sections when the multiply charged ions of these elements colliding with hydrogen atoms are key important.…”

Section: Introductionmentioning

confidence: 99%

Target electron removal in C⁵⁺ + H collision

Atawneh

Tőkési

2021

We present target ionization and charge exchange cross sections in a collision between C5+ ion and H atom. We treat the collision dynamics classically using a four-body classical trajectory Monte Carlo (CTMC) and a four-body quasi-classical Monte Carlo (QCTMC) model when the Heisenberg correction term is added to the standard CTMC model via model potential. The calculations were performed in the projectile energy range between 1.0 keV/amu and 10 MeV/amu. We found that the cross sections obtained by the QCTMC model are higher than that of the cross sections calculated by the standard CTMC model and these cross sections are closer to the previous experimental and theoretical data. Moreover, for the case of ionization, we show that the interaction between the projectile and the target electrons plays a dominant role in the enhancement of the cross sections at lower energies.