Measurements of rotational transform profile using Motional Stark Effect spectroscopy

利用运动斯塔克效应光谱测量螺旋等离子体的旋转变换曲线，研究磁剪切与输运和MHD不稳定性之间的关系。2003财政年度，由于磁场局部螺距角由环形电流和普菲许-施吕特电流决定，建立了各种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中，购买并测试了冷却CCD探测器，并开发了CCD探测器的软件。2004财政年度，采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），并在大螺旋装置上测量了初步数据。利用运动斯塔克效应光谱学测量的磁场俯仰角计算等离子体特性的旋转变换的计算机代码。为了研究中性束电流驱动改变旋转变换的有效性，在LHD和CHS中进行了电流驱动实验。2005财政年度，在当前的驱动实验中，用中性注入的bema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，研究了等离子体约束的变化规律。随着中心旋转变换的增大，磁切变减小，研究了MHD的不稳定性。实验研究了旋转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.