The fast ion dynamics and the associated heat load on the plasma facing components in the KSTAR tokamak were investigated with the orbit following Monte-Carlo (OFMC) code in several magnetic field configurations and realistic wall geometry. In particular, attention was paid to the effect of resonant magnetic perturbation (RMP) fields. Both the vacuum field approximation as well as the self-consistent field that includes the response of a stationary plasma were considered. In both cases, the magnetic perturbation (MP) is dominated by the toroidal mode number n = 1, but otherwise its structure is strongly affected by the plasma response. The loss of fast ions increased significantly when the MP field was applied. Most loss particles hit the poloidal limiter structure around the outer mid-plane on the low field side, but the distribution of heat loads across the three limiters varied with the form of the MP. Short-timescale loss of supposedly well-confined co-passing fast ions was also observed. These losses started within a few poloidal transits after the fast ion was born deep inside the plasma on the high-field side of the magnetic axis. In the configuration studied, these losses are facilitated by the combination of two factors: (i) the large magnetic drift of fast ions across a wide range of magnetic surfaces due to a low plasma current, and (ii) resonant interactions between the fast ions and magnetic islands that were induced inside the plasma by the external RMP field. These effects are expected to play an important role in present-day tokamaks.
KSTARトカマクにおける高速イオン動力学と、プラズマ対向機器への関連する熱負荷を、いくつかの磁場配位および現実的な壁形状のもとで軌道追跡モンテカルロ(OFMC)コードを用いて調べた。特に、共鳴磁場摂動(RMP)場の効果に注目した。真空場近似と、静止プラズマの応答を含む自己無撞着場の両方を考慮した。どちらの場合も、磁場摂動(MP)はトロイダルモード数 n = 1 が支配的であるが、その構造はプラズマ応答によって強く影響される。MP場を印加すると、高速イオンの損失は有意に増加した。ほとんどの損失粒子は、低磁場側の外側中平面周辺のポロイダルリミター構造に衝突したが、3つのリミター間の熱負荷分布はMPの形態によって変化した。また、良好に閉じ込められていると考えられていた共通過高速イオンの短時間スケールの損失も観測された。これらの損失は、高速イオンが磁気軸の高磁場側のプラズマ内部深くで生成された後、数ポロイダル周回以内に始まった。調べた配位では、これらの損失は2つの要因の組み合わせによって促進される: (i) 低プラズマ電流による広範囲の磁気面にわたる高速イオンの大きな磁気ドリフト、および (ii) 外部RMP場によってプラズマ内部に誘起された磁気島と高速イオンとの間の共鳴相互作用。これらの効果は、現在のトカマクにおいて重要な役割を果たすと期待される。