Abstract Details
Abstracts
Author: Sergey Medvedev
Requested Type: Poster
Submitted: 2025-03-13 06:57:20
Co-authors: A.Dnestrovskii, M.Gryaznevich, F.Janky, S.McNamara, M.Romanelli
Contact Info:
Tokamak Energy Ltd
173 Brook Drive
Milton Park, Oxfordshire OX14 4SD
United Kingdom
Abstract Text:
Long pulse operation is a highly beneficial feature for a commercially viable fusion power plant. Largely non-inductive current drive with high bootstrap current fraction is the main feature to be explored in tokamak-based fusion power plant prototype. Investigations of no-wall ideal MHD stability for steady state current density profiles with qmin>2 and low internal inductance reveals n=1 kink peeling-ballooning modes setting poloidal beta limit rather than the toroidal beta limit. This is described by a new beta limit scaling which exposes the dependence on plasma shaping missing from the conventional Troyon scaling for normalized beta values. In particular, the beta limit degrades with a transition from double null to single null plasma. The global nature of the external kink modes makes the wall stabilization quite efficient, but the active kink RWM control is required for that. Profile dependence, and pedestal height in particular, are other factors of uncertainty for reactor relevant steady state scenario. However, the pedestal height within the edge localized peeling-ballooning mode stability limits does not considerably change the global beta limit. On the other hand, axisymmetric n=0 RWM (“vertical”) stability is rather sensitive to the pedestal height with self-consistent free boundary plasma shape: higher bootstrap current in the pedestal leads to decreasing cross section squareness and strong localized mode destabilization unless passive conductors are close to the X-points. New plasma simulator SOPHIA based on the ASTRA/SPIDER code with adaptive flux grid capability provides a unique platform for space and time resolved integrated modelling in the frame of self-consistent free boundary plasma evolution for tokamak scenario design and control. First examples of SOPHIA vertical control for fusion power plant design points are demonstrated.
Characterization: 5.0
Comments: