Boonyarit Chatthong and Thawatchai Onjun

pp. 375 - 387

Abstract

Two different approaches for predicting plasma toroidal velocity ( v_∅
) are developed and used in self-consistent
simulations of H-mode plasmas with the presence of ITB using BALDUR integrated predictive modelling code. In the first
approach, the toroidal velocity depends on the plasma current density; while in the second approach the toroidal velocity is
directly proportional to the ion temperature. The profile of v_∅
 is used to calculate the ω_ExB flow shear which is a main mechanism for plasma transport suppression, leading to the ITB formation. In all simulations, the core transport model is a combination of NCLASS neoclassical transport and semi-empirical Mixed Bohm/gyro-Bohm model that includes the ITB effects.
The boundary condition is set at top of the pedestal and is estimated using a pedestal model based on a combination of
magnetic and flow shear stabilization pedestal width scaling and an infinite-n ballooning pressure gradient. Two toroidal
velocity models are used to simulate the time evolution of plasma temperature and density profiles of 10 JET discharges.
The root mean square error (RMSE) is used to compare simulation results of those 10 JET discharges with experimental data.
It is found that RMSE of T_i
, T_e
, n_e
 are 28.1%, 31.8%, and 15.0% for the first toroidal velocity model and 25.5%, 30.2%, and
15.1% for the second toroidal velocity model, respectively. Furthermore, this suite of codes is used to predict the ITER
performance under standard type I ELMy H-mode. It is found that the simulation yields formation of a narrow ITB near r/a =
0.7 in the simulation using the current density dependent model and a wide ITB from r/a = 0.5 to 0.8 in the simulation using
the ion temperature dependent model. The average of central ion temperature, total fusion power output and alpha power
are predicted to be 36 keV, 159 MW and 492 MW for the current density dependent model and 49 keV, 218 MW and 786 MW
for the ion temperature dependent model, respectively. 

Keywords

• ITB
• H-mode
• toroidal velocity
• BALDUR
• JET
• ITER