Dependence of particle and power dissipation on divertor geometry and plasma shaping in DIII-D small-angle-slot divertor

Wang, Huiqian; Ma, Xinxing; Maurizio, R.; Guo, H.Y.; Thomas, D. M.; Watkins, J. G.; Shafer, M.W.; Hyatt, A.L.; Moser, Auna; Ren, Jun; McLean, A.G.; Scotti, F.; Stangeby, P.C.

doi:10.1016/j.nme.2022.101301

Cited by 2 publications

(3 citation statements)

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“…The reduction in detachment density is ∼12% and ∼8% for ion − → B ×∇B drift into (figure 6(e)) and out of the slot (figure 6(f )), respectively. This effect is consistent with multiple SAS experiments [22,24,25] and is observed for a range of plasma currents and heating powers (from separate DIII-D experiments, see [26]).…”

Section: Impact Of Strike Point Position On Detachment Onsetsupporting

confidence: 90%

“…This reduction is ∼22% for strike point on the vertex (from 6.4 to 5 10 19 m −3 , see figure 5(d)) and ∼7% for strike point on the inner slant (from 5.6 to 5.2 10 19 m −3 , see figure 5(e)), with ion − → B ×∇B drift into the slot. The effect is captured by SOLPS-ITER simulations, showing a comparable ∼20% reduction of the upstream separatrix density required to achieve 10 eV near the strike point with in-slot compared to main-chamber fuelling (figure 5(b)), and is consistent with the impact seen in SAS experiments [22]. The SOLPS-ITER simulations have 4 MW of injected power, uniform transport coefficients (D = 0.15 m 2 s −1 and χ e = χ i = 0.5 m 2 s −1 ) enhanced by 5 in the divertor and private flux region (PFR) regions beginning at the X-point elevation, and neutral puff rates ranging from 4 to 14 10 21 D s −1 with the MC valve and from 2 to 8 10 21 D s −1 with the in-slot valve.…”

Section: Impact Of In-slot Fuelling On Detachment Onsetsupporting

confidence: 72%

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Experiments on plasma detachment in a V-shaped slot divertor in the DIII-D tokamak

Maurizio,

Thomas,

et al. 2024

Nucl. Fusion

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Experiments in DIII-D demonstrate that the upstream plasma density to detach an un-pumped slot divertor is similar for a V-shaped and a flat-end slot, despite significantly higher neutral pressure in the V-shaped slot and in contrast to SOLPS-ITER predictions. The detachment threshold can be reduced by using in-slot instead of main-chamber gas fuelling or by placing the strike point on the inner slanted slot baffle instead of the slot end, as described by simulations with full drift physics. When increasing the plasma line-averaged density (without extrinsic impurities), the transition to detachment in DIII-D slot divertor is sharp and requires a high value of plasma density with the ion B → × ∇ B drift into the slot, whereas it is smooth and requires a lower value of plasma density with the opposite drift direction, in accord with detachment experiments in the DIII-D open lower divertor. Unique experiments on DIII-D and comparison to advanced simulations expand the scientific understanding of slot-shaped divertors, considered highly desirable for next step fusion devices.

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Section: Impact Of Strike Point Position On Detachment Onsetsupporting

confidence: 90%

Section: Impact Of In-slot Fuelling On Detachment Onsetsupporting

confidence: 72%

Experiments on plasma detachment in a V-shaped slot divertor in the DIII-D tokamak

Maurizio,

Thomas,

et al. 2024

Nucl. Fusion

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“…Core optimization through current and pressure profile control will be investigated using a 1 MW LFS helicon HHFW CD system [76], a unique HFS lower hybrid CD system [77], and increased ECH power including additional top launch injectors. Edge plasma and plasma materials interactions solutions will be explored using a new high power closed divertor geometry [78] and a wall insertion test station for macroscopic scale innovative materials testing. For the longer term, major upgrades to both the normalized and absolute capabilities of the facility are being considered to increase performance and flexibility in order to resolve the physics and techniques for integrated core-edge solutions in the relevant physics regimes for future fusion reactors.…”

Section: Summary and Future Plansmentioning

confidence: 99%

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

et al. 2022

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DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L–H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.

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Dependence of particle and power dissipation on divertor geometry and plasma shaping in DIII-D small-angle-slot divertor

Cited by 2 publications

References 17 publications

Experiments on plasma detachment in a V-shaped slot divertor in the DIII-D tokamak

Experiments on plasma detachment in a V-shaped slot divertor in the DIII-D tokamak

DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy

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