Study of Potential Structural Reformation with multi-channel measurements using heavy ion beam

在2000年至2001年的前两个财政年度，我们在原有的重离子束探测系统的基础上，又构建了一个新的重离子束探测系统（HIBP）。新HIBP位于与旧HIBP在环面方向上相距90度的位置。在建设期间，我们也进行了实验努力，以进一步了解分岔特性。在这些实验中，我们获得了关于分岔模式和迟滞存在的新发现，从而实现了改进约束状态。这些结果发表在《核聚变》杂志上。此外，包括CHS在Higashiyama站点时的相位结果在内的综合论文也发表在题为“等离子体中的分岔现象”的书中。在2001财政年度，新HIBP的建设已经完成，并使用两个HIBP系统在ecr加热的低电子密度0.5 × 10^<13> cm^<-3>的CHS等离子体上进行了第一次实验。利用这两个hibp在两个不同的径向位置同时测量，可以得到电脉冲（自组织振荡）过程中电势结构的时空演化信息。这一结果已在2010年国际原子能机构核聚变能会议上作为一篇论文发表。结果概要如下：1)在脉动过程中，势滴由中心向外传播，且传播速度相当快。如果将传播过程表示为扩散过程，则系数为D-100m^2/s。ii)发现边缘密度与中心电位行为密切相关。观测结果表明，该现象具有非局域性；iii)在同一放电序列中，观察到电势的相干涨落。考虑了磁面波动与Alfven模态的关系，并推导了相应的磁面位移。

In the first two fiscal years from 2000 to 2001, we had constructed a new heavy ion beam probe (HIBP) system on CHS in addition to the old HIBP system. The new HIBP is located at the position away from the old one by 90 degree in toroidal direction. During this period of the construction, we had also made experimental efforts to obtain further understanding of bifurcation characteristics. In these experiments, we have obtained new findings about patterns of bifurcation and existence of hysteresis for realization of the status with improved confinement. These results have been published in Nuclear Fusion. Furthermore, the integrated paper including the results obtained in the phase when CHS is in the Higashiyama site has been also published in the book entitled 'Bifurcation phenomena in plasmas'. In the fiscal year 2001, the construction of the new HIBP has been finished, and the first experiments using two HIBP systems have been done on the ECR-heated CHS plasma with a low electron density of 0.5x10^<13> cm^<-3>. The simultaneous measurements at two different radial positions with these two HIBPs give us information of spatio-temporal evolution of potential structure during electric pulsation (self-organized oscillation). The result has been presented as a post dead line paper in 19^<th> IAEA conference on fusion energy. The outline of the results is following, i) During the pulsation, the potential drop propagates from the center to the outside, and the propagation is quite high. If we express the propagation as diffusion process, the coefficient is D-100m^2/s. ii) It is found that the edge density is strongly correlated with central potential behavior. The observation shows non-local nature of this phenomenon, iii) In the same series of discharges, coherent fluctuation has been observed in potential. The fluctuation is considered to relate with Alfven modes and the corresponding displacement of magnetic surface has been deduced.