超声分子束注入激发约束改善过程中边缘湍流的实验研究

Compared with gas puffing, Supersonic Molecular Beam Injection(SMBI) could significantly improve the confinement performance in magnetically confined fusion plasma. SMBI stimulated L-H transition has been frequently observed in many experiment devices. The research of underlying physics has started from various angles. It is well know from both theory and experiment that, the enhancement of poloidal flow shear and suppression of turbulent transport are important physics mechanism for L-H transition. This project will apply the well-developed SMBI in HL-2A/M as the fueling method, Langmuir probe and gas-puffing imaging system as the edge turbulence diagnostics. We will modify the hardware and develop the data processing software for newly installed Gas-puffing imaging system in HL-2A. In the experiment, the SMBI parameters like injection timing and injection intensity et al will be precisely controlled to suppress the edge turbulence and realize L-H transition; from the trigger timing of SMBI to the timing of L-H transition, we will measure and analyze the evolution of turbulence features like turbulence amplitude and poloidal flow shear et al, to understand the physics mechanism for SMBI induced confinement improvement.

相对于普通送气（GP），超声分子束注入（SMBI）能够显著改善磁约束聚变等离子体的约束性能，在很多实验装置上观测到SMBI激发的L-H转换，其物理机制的研究已经从多个角度展开。理论和实验普遍认为，极向流剪切的增强和湍流输运的抑制是L-H转换的重要物理机制。本项目将用HL-2A装置上已经成熟的SMBI作为送气手段，用静电探针和送气成像系统等作为边缘湍流诊断手段，并对已经安装的送气成像系统进行硬件改进和数据分析软件开发。在实验上通过精确控制SMBI注入时刻、送气强度等参量来控制边缘湍流，并实现L-H转换；在超声分子束注入后至L-H转换的过程中，对湍流幅度和极向流剪切等湍流特征的演化过程进行测量分析，理解SMBI改善约束的物理机制。

相对于普通的喷气（GP）加料，弹丸加料（PI）和强脉冲送气（超声分子束-SMBI和高强度送气-HIGP）可以改善磁约束等离子体的约束性能，在DIII-D装置上观测到PI激发的L-H转换，在HL-2A和Heliotron J等装置上观测到SMBI / HIGP激发的L-H转换。理论和实验普遍认为，极向流剪切的增强和湍流输运的抑制是L-H转换的重要物理机制。本项目利用HL-2A装置上已经成熟的SMBI作为加料手段，充分利用各种诊断方法，研究了强脉冲送气对等离子体的湍流和主要参数的影响；发展和完善了送气成像系统（GPI）的硬件设备和数据分析编码。在强脉冲送气后的短时间内观测到边缘压力梯度降低，剪切流被抑制，湍流增强，约束下降；一段时间（10-20ms）后压力梯度和剪切流恢复，湍流降低，约束变好。这说明强脉冲送气对等离子体主要参数和湍流输运均具有较强的影响。另外，利用GPI诊断，观测到等离子体边缘区域的blob及其向外移动过程；在国际合作研究中，用GPI诊断观测到等离子体边缘由快离子激发的低频不稳定性。证明了高速相机是聚变等离子体的重要诊断工具。