TRANSPORT SIMULATION OF NEUTRAL BEAM HEATED ASDEX PLASMA IN THE L AND H REGIMES
Local transport in the L (low beta-p) and H (high beta-p) types of double-null divertor discharges in ASDEX is investigated by computer modelling. For the L type, two subregimes with different local transport behaviour can be distinguished: Homogeneous electron heat diffusivities chi-e=chi-e or flat chi-e profiles and diffusion coefficients D = 0.2chi-e are found for chi-e < 5.2 X 10**4 cm**2.s -1- (L-I), while above this limit, steep chi-e and flat D profiles are determined (L-II). The observed decrease confinement time with increasing neutral injection power is found to be due to enhancement of the electron heat diffusivity. In the L-II regime, chi-e strongly increases with radius, while the diffusion coefficient remains flat. The diffusivities show a rather weak dependence on time as in the L-I regime. In both L regimes they rise with increasing injection power and decreasing plasma current, but are independent of density. In the H regime, transport is characterized by flat chi-e profiles and D = 0.2chi-e. The diffusivities are reduced by a factor of about two in the whole plasma compared with the L type. They show the variation with plasma current found in L discharges and are also independent of density. One more common feature of L and H regimes is that the ion heat diffusivity is in the range of 1 to 3 times the neoclassical values.
Bibliographic Reference: NUCLEAR FUSION, VOL. 23 (1983), NO. 10, PP. 1293-1300
Record Number: 1989122086400 / Last updated on: 1987-01-01
Available languages: en