Measurements of rotational transform profile using Motional Stark Effect spectroscopy

本研究的目的是通过运动斯塔克效应谱测量旋转变换轮廓，研究螺旋等离子体中磁场剪切和输运与MHD不稳定性的关系。2003财年，由于磁场的局部俯仰角由环形电流和有限β的Pfisch-Schluter电流决定，因此建立了不同压力剖面和电流剖面的等离子体平衡数据库。在运动斯塔克效应光谱的制备过程中，购买和测试了制冷的CCD探测器，并开发了相应的软件。2004财年，利用运动斯塔克效应的偏振光谱仪(运动斯塔克效应光谱系统)和在大型螺旋装置上的测量获得了初步数据。计算旋转变换的计算机代码，根据运动斯塔克效应光谱测量的磁场的俯仰角确定等离子体特性。为了研究中性束流驱动改变旋转变换的有效性，在LHD和CHS上进行了电流驱动实验。2005财年，在注入中性BMA的电流驱动实验中测量了旋转变换的径向分布。通过电流驱动减小了中心旋转变换，并研究了等离子体约束的变化。通过减小磁剪切量来研究MHD不稳定性，并通过增加中心转动变换来研究。实验研究了转动变换对等离子体约束和MHD不稳定性的影响。

The object of the research is to study a relation between magnetic shear and transport and MHD instability in helical plasma by measuring rotational transform profiles with Motional Stark Effect spectroscopy.In 2003 fiscal year, the database of plasma plasma equilibrium for various pressure profile and current profile are developed because a local pitch angle of magnetic field is determined by the toroidal current and Pfirsch-Schluter current due to finite beta. In the preparation of Motional Stark Effect spectroscopy, cooled CCD detector is purchased and tested and software for the CCD detector has been developed.In 2004 fiscal year, the polarization spectrometer using Motional Stark Effect (Motional Stark Effect spectroscopy system) and a preliminary data was taken with the measurement in Large Helical Device. The computer code to calculate the rotational transform determining plasma characteristics from the pitch angle of magnetic field measured with the Motional Stark Effect spectroscopy. In order to study the validity of neutral beam current drive in changing the rotational transform, the current drive experiments have been done in LHD and CHS.In 2005 fiscal year, radial profiles of rotational transform are measured in the current drive experiment with neutral bema injection. Central rotational transform is reduced by the current drive and how the plasma confinement changes was studied. MHD instability is studied by reducing magnetic shear with the increase of central rotational transform. The effects of rotational transform on the plasma confinement and MHD instability are studied in these experimental research.