ICRF operation with improved antennas in ASDEX Upgrade with W wall

V. Bobkov, M. Balden, R. Bilato, F. Braun, R. Dux, A. Herrmann, H. Faugel, H. Fünfgelder, L. Giannone, A. Kallenbach, H. Maier, H.W. Müller (+7 others)
2013 Nuclear Fusion  
Experiments with boron-coated side limiters of two antennas operated together in 2012 showed that the side limiters are responsible to more than half of the increased W content in the plasma. Together with the contribution from the other limiter tiles, not replaced in 2012, the limiters accounts for at least 2/3rds of the W content. A modified test two-strap ICRF antenna in ASDEX Upgrade with broad limiters and narrow straps has shown an improved operation with full W-wall in 2011/2012
more » ... 2011/2012 campaigns with up to a 40% lower rise of W concentration allowing more stable operation at low deuterium gas injection rate. Limiter spectroscopy measurements indicate up to a 40% reduction of the rise of the W sputtering yield during ICRF power, measured under the assumption of negligible influence of geometry variations and reflections on the measurements. The boron limiters on two antennas together with the improved broad-limiter antenna allowed a successful ICRF operation in 2012. As a part of long-term strategy of antenna design development, two threestrap antennas with phase and power balance control for reduction of E || are planned for installation in the future.
doi:10.1088/0029-5515/53/9/093018 fatcat:aze5ym6xnfdytdxngb4dkhdfam