The role of divertor pumping in plasma detachment and particle exhaust in a closed divertor
Bibliographic record
Abstract
Abstract The impact of pumping on divertor power dissipation and particle exhaust in a closed divertor with flat target configuration is examined using SOLPS modeling. A closed divertor can increase neutral pressure and enhance radiative dissipation; accordingly it has been proposed as a direction for the design of advanced divertors to achieve detachment at as low an upstream plasma density as possible. However, the necessity to pump the closed divertor results in a reduction of the high density and pressure of neutrals near the target. The quantitative effect of this reduction on the achievement of detachment is assessed here. By independently varying both the pumping speed S using different pump opening surface areas, together with the upstream plasma density at the outside midplane, n e , s e p OMP , it is established quantitatively how the pump exhaust rate, Q exh (particles/s), depends on these two quantities. As expected, pumping increases the detachment onset density, n e , s e p O M P , o n s e t ; however, for S = 40 m3 s−1, it is shown that Q exh = 1 kA and detachment onset—as defined by a peak T e at the outer target of ∼5 eV—can be obtained simultaneously, which is consistent with DIII-D requirements for particle and energy exhaust. By placing the pump surface at different distances from the target, it is established how the pump location affects Q exh, which in turn affects the divertor plasma conditions, including achievement of detachment. High pumping speed reduces neutral density and radiated power, thus increasing T e and the heat flux to the target. The essential difference between the various pump locations is the ratio of Q exh to the total number of neutral deuterium particles plus carbon particles (atoms and ions) in the outer divertor, f exh = Q exh/N tot-OD. It was found that the best pump location is near the target at the CFR (common flux region) side of the closed divertor slot. Pumping at the PFR (private flux region) side near the target gave similar results, indicating flexibility with regard to pump location in closed divertors with a flat target plate.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".