EAST托卡马克稳态氘弹丸注入触发蛇形振荡及L-H转换的物理实验研究

发布时间：2017-12-28 02:13

本文关键词：EAST托卡马克稳态氘弹丸注入触发蛇形振荡及L-H转换的物理实验研究　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：弹丸注入作为一种先进的等离子体加料技术,已经被未来聚变装置ITER选定为主要的加料手段。弹丸注入的作用不仅仅局限于简单的等离子体加料,合理地利用弹丸注入甚至可以控制等离子体MHD行为和输运。EAST装置作为一个全超导托卡马克装置,发展了一套稳态10Hz弹丸注入系统,并利用该系统开展了一系列弹丸注入加料及等离子体控制的实验研究。本论文首先针对EAST装置上弹丸注入对等离子体基本行为的影响展开了研究,发现弹丸注入可以引起等离子体密度峰化和储能的上升,证明了弹丸是一种优秀的等离子体加料手段。进一步实验分析表明,EAST装置上弹丸的等离子体加料效率(进入等离子体中的弹丸粒子数/单个弹丸的总粒子量)大约为30%,而高场侧注入能实现最高的等离子体加料,在理想情况下可以达到～40%。同时也发现随着辅助加热功率的升高,等离子体径向漂移作用变强,弹丸的加料效率会有所下降,粒子在等离子体中滞留时间也会下降。此外,还对H模情况下弹丸注入引起的ELM行为进行了简要的分析,发现大尺寸弹丸注入可能会导致等离子体约束变差,甚至从H模退回到L模。这些初步的实验结论为EAST装置上开展更进一步的实验研究提供了参考和数据积累。而后针对弹丸注入对等离子体芯部MHD行为影响开展了深入的实验研究,研究发现在欧姆加热条件下弹丸穿越等离子体q=1面可以触发强烈的芯部MHD行为——蛇形振荡现象。弹丸触发蛇形振荡的基本原理是弹丸在q = 1面附近引入很大的密度和温度扰动,帮助局域范围内形成磁岛,并最终发展成为蛇形振荡。EAST观察到蛇形振荡现象具有影响范围广,持续时间长的特点,需要结合阻尼撕裂模和分支螺旋平衡状态理论才能合理解释。弹丸触发的蛇形振荡的实验研究是一种关于影响和控制等离子体芯部MHD行为的全新尝试,对于未来相关的实验研究具有指导意义。最后还开展了关于弹丸注入触发L-H转换的实验研究,研究发现通过边界弹丸的注入可以帮助等离子体边界输运垒的建立并使等离子体提前进入H模。实验中还发现EAST装置上的弹丸注入能够有效降低等离子体L-H转换阈值功率10%,且通过估算边界径向电场的方式,证明了弹丸消融引起了等离子体边界径向电场剪切的增大,从而抑制了湍流并建立其边界输运垒,最终实现H模。弹丸触发L-H转换实验研究能够帮助了解L-H转换期间等离子体各参数变化的因果关系,对于理解等离子体L-H转换的深层机制具有极其重要的意义。通过EAST装置上开展的弹丸注入实验研究,充分证明了弹丸是一种先进的等离子体加料和控制手段,同时也为未来ITER装置开展弹丸物理实验研究提供了数据积累。在上述实验研究的基础上未来将进一步开展深层次的弹丸注入实验研究,期待在未来得到更多更有意思的实验结果。
[Abstract]:As an advanced plasma feeding technology, the injection of projectiles has been selected as the main means of feeding in the future fusion device ITER. The effect of projectile injection is not only limited to simple plasma feeding, it is reasonable to use the injection of projectiles to even control the MHD behavior and transport of plasma. As a fully superconducting tokamak device, EAST has developed a set of steady 10Hz projectile injection system, and has carried out a series of experimental research on pellet injection charging and plasma control using this system. In this paper, we first studied the influence of projectile injection on the basic behavior of plasma in the EAST device. It was found that the injection of a projectile can cause the plasma density to peak and the energy storage to rise. It is proved that the projectile is an excellent plasma feeding method. Further experiments show that the plasma fuelling efficiency on EAST device (projectile projectile into particles in plasma / total number of single particle projectile volume) is about 30%, while the high field side can achieve the highest plasma charging, in the ideal case can reach to 40%. Meanwhile, it is also found that with the increase of auxiliary heating power, the radial drift of plasma becomes stronger, and the feeding efficiency of pellets will decrease, and the residence time of particles in plasma will also decrease. In addition, a brief analysis of ELM behavior caused by projectile injection in H mode is also made. It is found that large scale projectile injection may lead to plasma confinement variation, and even retreat from H mode to L mode. These preliminary experimental conclusions provide reference and data accumulation for further experimental research on the EAST device. Then, the influence of projectile injection on the MHD behavior of plasma core is studied. It is found that under the ohmic heating condition, projectile traversing the plasma q=1 surface can trigger strong core MHD behavior -- serpentine oscillation. The basic principle of projectile triggered snake like oscillation is that a large density and temperature disturbance is introduced near the q = 1 surface, which helps to form Magnetic Island in the local area and eventually develop into snake like oscillation. EAST observed that the serpentine oscillation has wide influence and long duration. We need to combine the theory of damping tearing mode and branch helix equilibrium state theory to explain it reasonably. The experimental research of snake triggered oscillation triggered by projectile is a new attempt to influence and control the MHD behavior of plasma core, and has guiding significance for future related experimental research. Finally, we carried out an experimental research on projectile injection triggered L-H conversion. It was found that the injection of boundary projectile can help the establishment of plasma transport barrier and advance plasma into H mode ahead of time. It is found that the EAST device on the pellet injection can effectively reduce plasma L-H switching threshold power of 10%, and by estimating the radial electric field boundary, that caused the increase of plasma ablation boundary shear of the radial electric field, thus inhibiting the turbulence and the establishment of the edge transport barrier, finally realizes the H mode. Experimental research on projectile triggered L-H conversion can help to understand the causal relationship between plasma parameters during L-H conversion, and is of great significance for understanding the deep mechanism of plasma L-H transformation. The projectile injection experiment carried out on the EAST device fully proves that the projectile is an advanced plasma feeding and control means, and it also provides data accumulation for future ITER device projectile physics experiment research. On the basis of the above experimental research, we will further carry out deep projectile injection experimental research in the future, and expect to get more interesting experimental results in the future.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TL631.24

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