Numerical modeling of lower hybrid current drive in fully non-inductive plasma start-up experiments on TST-2
Numerical modeling of lower hybrid current drive in fully non-inductive plasma start-up experiments on TST-2
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TST-2 上全无感等离子体启动实验中较低混合电流驱动的数值模拟
DOI：
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
Y. Yoshida
中科院分区：
文献类型：
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作者：
N. Tsujii;Y. Takase;A. Ejiri;T. Shinya;H. Togashi;S. Yajima;H. Yamazaki;C. Moeller;B. Roidl;M. Sonehara;W. Takahashi;K. Toida;Y. Yoshida
由于球形托卡马克中心螺线管没有足够的空间提供中子屏蔽，因此无感等离子体启动是一个关键问题。在TST-2球形托卡马克装置上研究了低杂波启动。由于球形托卡马克的低磁场，在等离子体电流上升期间，等离子体密度需要保持在非常低的值，使得等离子体芯保持可接近LH波。然而，我们已经发现，需要更高的密度来维持更大的等离子体电流。可实现的等离子体电流受到TST-2的最大操作环向场的限制。LH电流驱动的最佳密度的存在和它的环向场依赖性解释通过基于射线追踪代码和福克-普朗克求解器的数值模拟。为了在相同的磁场下获得更高的密度，除了现有的舷外发射天线外，最近还安装了顶部发射天线。当从顶部天线发射功率时，观察到密度极限增加，与数值预测一致。
Non-inductive plasma start-up is a critical issue for spherical tokamaks since there is not enough room to provide neutron shielding for the center solenoid. Start-up using lower hybrid (LH) waves has been studied on the TST-2 spherical tokamak. Because of the low magnetic field of a spherical tokamak, the plasma density needs to be kept at a very low value during the plasma current ramp-up so that the plasma core remains accessible to the LH waves. However, we have found that higher density was required to sustain larger plasma current. The achievable plasma current was limited by the maximum operational toroidal field of TST-2. The existence of an optimum density for LH current drive and its toroidal field dependence is explained through a numerical simulation based on a ray tracing code and a Fokker–Planck solver. In order to access higher density at the same magnetic field, a top-launch antenna was recently installed in addition to the existing outboard-launch antenna. Increase in the density limit was observed when the power was launched from the top antenna, consistently with the numerical predictions.