The Role of Plasma-Molecule Reactions in Influencing detachment.

热排放是未来聚变堆的一个关键问题，需要通过偏滤器等离子体分离来缓解，在偏滤器等离子体分离过程中，偏滤器等离子体在到达偏滤器靶板的过程中经历动量、功率和粒子通量的减少。长腿、强遮挡的偏滤器室加强了等离子体-中性相互作用(MAST-U、TCV、STEP、SPARC、ARC)并促进分离。在这种偏滤器中，等离子体-分子碰撞以及等离子体化学可以发挥重要作用。本研究通过分析MAST-U和TCV的数据，并将其与简化模型和模拟结果进行比较，为等离子体-分子动力学提供了一个新的视角。这些机器上的高分辨率D2 Fulcher带测量(通过偏滤器光谱)允许获得分子的摆动分布，提供关于等离子体-分子能量和动量转移和相互作用的信息。对MAST-U(4000-9000K)和TCV(2000-5000K)的转动温度[3]和振动分布(v=0，1，2，3)进行了详细的时间和空间分辨分析，表明了转动分布和振动分布之间的联系。研究了不同的偏滤器配置(Super-X、加长的MAST-U和传统的MAST-U)、挡板(TCV中有和没有筒仓挡板)以及两种装置中不同的加油位置和加热水平。我们发现在偏滤器整体冷却之前的附加和分离状态下，旋转温度升高。一个简化的模型，包括离子和分子之间弹性碰撞过程中的能量传递、分子寿命和传输时间，与这些发现是一致的。尾气模拟也是一致的。这种在高中性压力下的弹性碰撞，再加上这些较长的分子寿命，会导致显著的能量和动量耗散--即加深脱离。参考文献[1]K.Verhaegh et al 2021 Nucl.Fusion 61 106014，[2]K.Verhaegh等人2023年核。Fusion 63 016014[3]N.Osborne等人2024年血浆物理。控制室。Fusion 66 025008

Heat exhaust is a critical issue for future fusion reactors and it will need to be mitigated through divertor plasma detachment, in which the divertor plasma undergoes a reduction in momentum, power and particle flux en-route to the divertor target plates. Long-legged, strongly baffled divertor chambers intensify plasma-neutral interactions (MAST-U, TCV, STEP, SPARC, ARC) and facilitate detachment. In such divertors, plasma-molecular collisions, as well as plasma chemistry, can play an important role.This study presents a new insight into plasma-molecular kinetics through analysis of data from MAST-U and TCV, and comparison of this with simplified models, and simulations. High resolution D2 Fulcher band measurements (via divertor spectroscopy) on these machines allow the rovibrational distribution of the molecules to be obtained, providing information on plasma-molecule energy and momentum transfer and interactions. Detailed temporally and spatially resolved analyses of the rotational temperatures in MAST-U (4000-9000 K) [3] and TCV (2000-5000 K), and the vibrational distributions in both devices (v = 0, 1, 2, 3), show a connection between the rotational and vibrational distribution. Different divertor configurations (Super-X, Elongated and Conventional in MAST-U); baffling (with and without SILO baffles in TCV); and different fuelling locations and heating levels in both devices, have been studied. We find that rotational temperature increases during attached and detached conditions before the overall cooling of the divertor. A simplified model including energy transfer during elastic collisions between ions and molecules; molecule lifetime; and transport time, are consistent with these findings. Exhaust simulations are also consistent. Such elastic collisions in high neutral pressures, combined with these longer molecular lifetimes, lead to significant energy and momentum dissipation - i.e. deepening detachment. An isotopic study has also been carried out on TCV.References:[1] K. Verhaegh et al 2021 Nucl. Fusion 61 106014,[2] K. Verhaegh et al 2023 Nucl. Fusion 63 016014[3] N. Osborne et al 2024 Plasma Phys. Control. Fusion 66 025008