Modelling of tungsten migration during limiter ramp-down in the ASDEX Upgrade divertor tokamak
Bibliographic record
Abstract
The suitability of tungsten as a plasma facing material in magnetic fusion devices is currently under investigation at the ASDEX Upgrade divertor tokamak. Recently, the complete central column, which is also used as a ramp-up and ramp-down limiter was covered with W coated carbon tiles. Experimentally, the transient limiter phases were identified to dominate the gross influx of eroded tungsten and thus they could have an effect on the post-campaign surface analysis measurements. Therefore, the migration of W during limiter contact was assessed using the DIVIMP impurity transport code. The results indicate that most of the tungsten eroded during the limiter phases is redeposited locally on the central column and that only an average of less than 10% of the eroded W is deposited somewhere else on the wall. Accordingly, campaign integrated surface analysis measurements of tungsten deposition in the divertor are not influenced by tungsten deposited during ramp-up or ramp-down. Moreover, the comparison of tungsten migration during the limiter phases and the much longer flat-top divertor phases is not contradictory to the experimental result that only about 10% of the tungsten, eroded at the central column, is found in the divertor by post-campaign tile analysis.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".