Current Drive in Spherical Tokamak Plasmas by the Lower Hybrid Wave

本研究的目的是证明球形托卡马克所需的等离子体电流可以由高频波驱动。用200MHz低杂波成功地驱动了超过10kA的等离子体电流。比较了3种天线的实验结果，得到了许多有助于物理理解的重要结果，如球形托卡马克位形的自形成、非线性波现象的波测量表征和快电子的X射线诊断表征、波数谱的优化以及新型天线的研制等。目前，电流驱动效率受到快速电子损失的限制，但根据数值模拟，通过在更高的磁场和更高的等离子体电流下操作，预计会有很大的改善。这些结果为提高聚变反应堆的经济竞争力提供了可能性。

The purpose of this research is to show that the plasma current needed for spherical tokamaks can be driven by high frequency waves. Plasma currents of over 10kA were driven successfully using the 200MHz lower hybrid wave. Comparing the experimental results obtained using 3 types of antennas, many important results that contribute to the physics understanding, such as self-formation of the spherical tokamak configuration, characterization of nonlinear wave phenomena by wave measurements and of fast electrons by X-ray diagnostics, optimization of wavenumber spectrum, and development of a new antenna, were obtained. Presently, the current drive efficiency is limited by fast electron losses, but according to numerical modeling, a large improvement is expected by operating at higher magnetic field and higher plasma current. These results open up a possibility of improving the economic competitiveness of a fusion reactor.