The X-Point radiating regime at ASDEX Upgrade and TCV

• DOI: 10.1016/j.nme.2023.101376
• Publication Date: 2023-01-30T07:54:14Z
• Authors: M. Bernert; S. Wiesen; O. Février; A. Kallenbach; J.T.W. Koenders; B. Sieglin; U. Stroth; T.O.S.J. Bosman; D. Brida; M. Cavedon; P. David; M.G. Dunne; S. Henderson; B. Kool; T. Lunt; R.M. McDermott; O. Pan; A. Perek; H. Reimerdes; U. Sheikh; C. Theiler; M. van Berkel; T. Wijkamp; M. Wischmeier
• Keywords: ASDEX Upgrade; Collisionality

Future fusion reactors require a safe, steady-state divertor operation. With deep detachment, which is typically induced by impurity seeding, the radiation concentrates in small region at X-point or on closed flux surfaces above X-point. This so-called radiator (XPR) moves further inside confined with increasing seeding and location can be actively controlled. At AUG, parameter space for operation an XPR was significantly extended, using active feedback location. The observed nearly whole operational of AUG high-densities high collisionality regime. ELM suppression consistently all cases where moved to significant height Direct measurements density temperature from around new Thomson scattering system indicate that remains (>30eV) only towards cools down further. In this cold core, reduces about 1eV. An also TCV injection nitrogen as extrinsic impurity. highlights wall material (W C TCV) machine size does not play role existence However, scenario appears less stable TCV. First experiments show necessity control XPR: Depending conditions storage, required level achieve changes. Both, low temperatures measured radially outside zone lower stability regime presence carbon are consistent predictions one-dimensional model XPR. would predict development might already exist before reaching solution.