Summary of the 3rd IAEA technical meeting on divertor concepts

Barbarino, Matteo; Leonard, A. W.; Asakura, N.; Jakubowski, M.; Kobayashi, M.; Lipschutz, B.; Neu, R.; Wang, Liang; Wischmeier, M.

doi:10.1088/1741-4326/ab9a0c

Cited by 4 publications

(3 citation statements)

References 16 publications

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“…This regime might be associated with the X-point MARFE [24,25] and in some sense is similar to it, however, we will not use this term, following the suggestion and reasoning introduced in [22]: in contrast to MARFE, the newly observed regime does not lead to the unstable plasma. Note, however, that in DIII-D experiments no observations of the radiating X-point regime is reported, while the increase of nitrogen seeding leads to confinement degradation or even to radiation collapse of the discharge [23,26].…”

Section: Introductionmentioning

confidence: 96%

Approaching the radiating X-point in SOLPS-ITER modeling of ASDEX Upgrade H-mode discharges

Senichenkov¹,

Rozhansky²,

Voskoboynikov³

et al. 2021

Plasma Phys. Control. Fusion

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In the present paper the ASDEX Upgrade (AUG) experimental trend of reaching the radiating X-point with nitrogen seeding is reproduced by SOLPS-ITER code modeling. In these experiments the whole divertor region below the X-point is cooled down by the impurity radiation if the seeding rate is large enough, and the maximal radiation is registered from the X-point region, or even from the confinement zone above the X-point. It is demonstrated that for constant seeding rate SOLPS-ITER simulations of the intensively seeded AUG discharges result in that the confined plasma goes into the radiation collapse as a certain threshold in seeding rate is exceeded. This threshold value increases with increasing discharge power. No stable regimes with the electron temperature below 5 eV in the confinement zone even above the X-point are achieved in the modeling if the seeding rate is large enough, in contrast to the experiment. However, such a regime may be achieved if the fueling, seeding and pumping rates are changing in time. Since the SOLPS-ITER code can simulate only steady state, another modeling strategy is chosen. The fueling and seeding rates are artificially reduced by 3 orders of magnitude and the impurity content is set to satisfy the condition that the ratio of electrons contribution originating from fuel atoms to ones coming from impurity atoms is about unity. It is suggested that the radial width of the cooled region in the confinement zone is of the order of the scrape-off layer width λ q , since it is driven by the same physics leading the energy flux to go from mostly radial to mostly parallel. Under these conditions, the radiative spot above the X-point behaves as the energy sink similarly to the energy sink near the divertor in the conventional regime. In extreme regimes (with large seeding rate), the width of the cold region inside the separatrix may exceed λ q , and up to 90% of discharge power can be radiated from the confined region. An estimate of the poloidal length of the radiative spot is suggested as well. Flow patterns of neutrals, deuterium ions, impurities, electric current and heat flows are analyzed for the regimes with intensive X-point radiation. The formation of an electric potential peak above the X-point is observed in the simulations, and the corresponding E × B drift flux appears to give the largest contribution to the main ion and impurity fluxes. This E × B drift flux together with the large ionization source change the parallel velocity with respect to its neoclassical profile. Consequently, the radial E field deviates from the neoclassical one, which might improve the turbulence suppression.

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Section: Introductionmentioning

confidence: 96%

Approaching the radiating X-point in SOLPS-ITER modeling of ASDEX Upgrade H-mode discharges

Senichenkov¹,

Rozhansky²,

Voskoboynikov³

et al. 2021

Plasma Phys. Control. Fusion

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“…In additional, the fishtail divertor, i.e. swinging SP, is also proposed for the active heat load control with the new divertor [34]. This asks for the large target area, which should satisfy the SP sweeping requirement.…”

Section: Introductionmentioning

confidence: 99%

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

Sang

Zhou

et al. 2021

Nucl. Fusion

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To demonstrate the performance of tungsten (W) as the divertor target material and to solve the power handling problem during high power long-pulse discharge, the upgrade of EAST lower divertor is planned. In this work, the physical design of the W divertor is presented by using 2D edge plasma code SOLPS and Monte Carlo impurity transport code DIVIMP. The optimized divertor geometry is proposed after systematic examination of target shapes, target slant angles and the pump opening locations. The performance of the designed divertor is further assessed by impurity seeding. By comparing the medium and high power discharges with argon (Ar) seeding, the differences on the divertor power radiation and impurity core accumulation are distinguished. The simulated effective ion charge Z eff fits well the scaling law, which is based on multi-machine database. Ar seeding and neon (Ne) seeding scans are carried out separately. The simulation results indicate Ar has higher power radiation efficiency than that of Ne, thus promoting the achievement of plasma detachment. However, the core compatibility with Ar is worse than with Ne. The W target erosion and W impurity transport during impurity seeding are simulated by the DIVIMP–SOLPS coupled modeling. It illustrates that under the similar divertor plasma conditions, Ar seeding causes more serious W erosion and more severe core contamination by W impurity, than Ne seeding. Finally, the divertor in–out asymmetry is studied by considering electromagnetic drifts. The simulation results manifest that the designed open vertical inner target reduces in–out asymmetry due to that its weak power radiation capability is offset by the ion flow driven by the drifts. In addition, the designed divertor is compatible with the quasi snowflake magnetic configuration. These studies will improve the understanding of W target sputtering and W impurity transport control during the radiative divertor discharges for CFETR/DEMO.

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“…Edge and divertor modeling in the highest plasma current case of I P = 5.5 MA, B T = 2.25 T, highest heating power of P in = 41 MW, and low separatrix density of n e,sep = 2.0 × 10 19 m −3 (the first scenario in table 2) with carbon wall have been performed with the SOLEDGE2D-EIRENE code [39]. Figure 14 illustrates the divertor heat load as a function of Ar seeding rate.…”

Section: Heat Load Handlingmentioning

confidence: 99%

Plasma physics and control studies planned in JT-60SA for ITER and DEMO operations and risk mitigation

Yoshida

Giruzzi

Aiba

et al. 2022

Plasma Phys. Control. Fusion

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A large superconducting machine, JT-60SA has been constructed to provide major contributions to the ITER program and DEMO design. For the success of the ITER project and fusion reactor, understanding and development of plasma controllability in ITER and DEMO relevant higher beta regimes are essential. JT-60SA has focused the program on the plasma controllability for scenario development and risk mitigation in ITER as well as on investigating DEMO relevant regimes. This paper summarizes the high research priorities and strategy for the JT-60SA project. Recent works on simulation studies to prepare the plasma physics and control experiments are presented, such as plasma breakdown and equilibrium controls, hybrid and steady-state scenario development, and risk mitigation techniques. Contributions of JT-60SA to ITER and DEMO have been clarified through those studies.

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Summary of the 3rd IAEA technical meeting on divertor concepts

Cited by 4 publications

References 16 publications

Approaching the radiating X-point in SOLPS-ITER modeling of ASDEX Upgrade H-mode discharges

Approaching the radiating X-point in SOLPS-ITER modeling of ASDEX Upgrade H-mode discharges

Design of EAST lower divertor by considering target erosion and tungsten ion transport during the external impurity seeding

Plasma physics and control studies planned in JT-60SA for ITER and DEMO operations and risk mitigation

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