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Impurity Behavior with Boron Coated Molybdenum Tiles in Alcator C-Mod
| Content Provider | Semantic Scholar |
|---|---|
| Author | Wukitch, Stephen James Garrett, M. Barnard, Harold S. Labombard, Brian Lin, Yang Lipschultz, B. Marmar, E. Ochoukov Reinke, M. L. Whyte, Dennis G. Wright, G. H. |
| Copyright Year | 2010 |
| Abstract | Reducing impurity production associated with ion cyclotron range of frequency (ICRF) operation to an acceptable level in high confinement plasmas, particularly with metallic plasma facing components (PFC), requires an understanding of the underlying sources and associated physical mechanisms. To identify important impurity source locations, we have vacuum plasma sprayed ~100 μm of boron (B) onto a limited number of molybdenum (Mo) tiles. The boron coated tiles are located on the outer divertor shelf, plasma and RF outboard limiters. The inner wall, upper and lower divertor plates remained uncoated. In ICRF heated H-modes, the core molybdenum levels have been significantly reduced and remained at low levels for increased amount of injected RF energy. The core Mo level also no longer scales with RF power in L-mode. With boronization and impurity seeding (typically nitrogen or neon), the plasma performance was sustained for higher number of joules than without seeding. Impurity seeding also improved the ICRF antenna performance, suppressed antenna faults, without a significant increase in core Mo levels. Spectroscopic monitoring of the plasma limiter found that the impurity profile at the limiter was centered near the plasma mid-plane and the profile did not change shape with plasma current. From post campaign inspection, the B coating was not significantly eroded except in locations where melting occurred or where it peeled with little evidence of a discernable pattern. Trace material analysis found that the B surface was contaminated with Mo and tungsten (W). Although these observations are indirect in nature, these disparate observations suggest the impurity source associated with ICRF operation is more complicated than strictly sputtering due to enhanced RF sheaths. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://www-pub.iaea.org/mtcd/meetings/PDFplus/2010/cn180/cn180_papers/exd_p3-37.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
