Study of electron cyclotron heating efficiency during tokamak plasma start-up with use of DINA and OGRAY codes

摘要

Fundamental O-mode resonance electron cyclotron heating (ECH) provides a reliable plasma initiation and start-up in many tokamaks [1,2] and it is planned to be used for ITER. In accordance with [3] approximately 2 MW of absorbed ECH power is necessary to assist the ITER plasma initiation and to support impurity burn-through in the initial plasma current ramp-up phase. Burn-through occurs when the electron temperature becomes sufficiently high (more than 100 eV) so that low Z impurity charge states are no longer produce a large fraction of the power radiated from plasma and the plasma is transferred to the low-resistance state' such that the applied electric field leads to efficient current ramp-up. On the other hand, the value of the absorbed fundamental O-mode ECH power injected into the plasma during the burn-through stage is quite sensitive to the electron temperature and density and can be very small [4]. This paper presents the modeling results of the absorption efficiency of ECH power in ITER tokamak plasma with scan of the plasma electron temperature and density values, which correspond to the burn-through phase and scan of the angle between the ray-tracing direction and the tangent to the magnetic surface at' the point of magnetic resonance. Interaction of electron cyclotron (EC) wave with plasma is analyzed with use of OGRAY code [5] for 2D plasma equilibrium obtained by use of DINA code [6].