High-confinement regime at high beta n values due to a changed behaviour of the neoclassical tearing modes
High confinement [with H = 1, ITERH-98 (y, 2)] at beta N = 2.3 has been found in ASDEX Upgrade discharges with existing (m, n) = (3, 2) neoclassical tearing modes (NTMs). The reason for the high confinement at high beta N values is a transition of the NTMs into the so-called frequently interrupted regime. In this regime, the NTM growth is frequently interrupted by sudden drops in amplitude. Because of the long NTM growth time, the resulting averaged NTM amplitude remains much smaller than the corresponding saturated value. As this behaviour with the beneficial effect on energy confinement has been confirmed at JET, such a high confinement regime at beta N greater than 2 might also be expected for ITER.
Bibliographic Reference: An article published in: Physical Review Letters, 87 (27), 275001, (31 December 2001).
Record Number: 200214633 / Last updated on: 2002-04-22
Original language: en
Available languages: en