Observations on the W-transport in the core plasma of JET and ASDEX Upgrade

TitleObservations on the W-transport in the core plasma of JET and ASDEX Upgrade
Publication TypeJournal Article
Year of Publication2013
AuthorsT. Putterich, R. Dux, R. Neu, M. Bernert, M.NA Beurskens, V. Bobkov, S. Brezinsek, C. Challis, J.W Coenen, I. Coffey, A. Czarnecka, C. Giroud, P. Jacquet, E. Joffrin, A. Kallenbach, M. Lehnen, E. Lerche, E. de la Luna, S. Marsen, G. Matthews, M-L Mayoral, R.M McDermott, A. Meigs, J. Mlynar, M. Sertoli, G.J van Rooij, ASDEX Upgrade Team, JET-EFDA Contributors
JournalPlasma Physics and Controlled Fusion

The W-transport in the core plasma of JET is investigated experimentally by deriving the W-concentration profiles from the modelling of the signals of the soft x-ray cameras. For the case of pure neutral beam heating W accumulates in the core ( r / a < 0.3) approaching W-concentrations of 10 −3 in between the sawtooth crashes, which flatten the W-profile to a concentration of about 3 × 10 −5 . When central Ion cyclotron resonant heating is additionally applied the core W-concentration decays in phases that exhibit a changed mode activity, while also the electron temperature increases and the density profile becomes less peaked. The immediate correlation between the change of magnetohydrodymanic (MHD) and the removal of W from the plasma core supports the hypothesis that the change of the MHD activity is the underlying cause for the change of transport. Furthermore, a discharge from the ASDEX Upgrade is investigated. In this case the plasma profiles exhibit small changes only, while the most prominent change occurs in the W-content of the confined plasma caused by the reduction of the fuelling deuterium gas puff. Concomintantly, the W-concentration profiles in the core plasma r / a < 0.2 steepen up reminescent to the well-known connection between central radiation and transport during cases with strong, established W-accumulation, while in the present analysis such a causality between the two during the onset of W-accumulation could not be pinned down. Both case studies exemplify that small changes of the core parameters of a plasma my influence the W-transport in the plasma core drastically.







Alternate TitlePlasma Phys. Control. Fusion

Go back one page.