Role of pre-ionization in NBI plasma start-up of Heliotron J using non-resonant microwave heating
Role of pre-ionization in NBI plasma start-up of Heliotron J using non-resonant microwave heating
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使用非谐振微波加热预电离在 Heliotron J 的 NBI 等离子体启动中的作用
DOI：
10.1088/1741-4326/ac2105
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Y. Nakamura
中科院分区：
文献类型：
--
作者：
S. Kobayashi;K. Nagasaki;K. Hada;T. Stange;H. Okada;T. Minami;S. Kado;S. Ohshima;K. Tokuhara;Y. Nakamura
本文报道了在非共振加热条件下，非共振2.45 GHz微波加热(P2.45 GHz；20kW)预电离在中性束注入(NBI)低束功率氦加速器等离子体启动中的作用。实验观察到，当非共振加热产生的种子等离子体密度足以启动等离子体时，在束流注入的早期阶段，低Z杂质的电子快速烧穿。束流加热到烧穿的时间随种子等离子体密度的降低而增加，实验上观察到了种子等离子体成功启动的临界密度条件。气体填充的适当时机对等离子体膨胀至关重要，因为束流填充并不重要。本研究开发的NBI启动的0维(0D)模型分析很好地再现了实验结果。0D模型阐明了采用预电离的NBI启动的物理机制，描述如下：(1)种子等离子体在束流注入后立即产生足够的束流离子，(2)束流离子加热促进背景中性粒子电离/解离的电子，(3)这一过程起到正反馈回路的作用，导致电子进一步加热到烧穿。零维模型分析表明，临界密度对应于束流离子对电子的加热等于由于传导和电离/解离引起的电子功率损失的状态。
Here, we report on role of pre-ionization using non-resonant 2.45 GHz microwave heating (P 2.45 GHz< 20 kW) in plasma start-up of neutral beam injection (NBI) for heliotron configurations in low beam power (P NB) under non-resonant heating condition. A rapid electron heating towards burn-through of the low-Z impurities was observed experimentally in the early phase of beam injection when the seed plasma density produced by the non-resonant heating was enough for the plasma start-up. Beam heating time to the burn-through increased with decreasing the seed plasma density and a critical density condition of the seed plasma for successful start-up was observed experimentally. Proper timing of the gas fuelling is critical for plasma expansion because the beam fuelling is not significant. A 0-dimensional (0D) model analysis of the NBI start-up developed in this study well reproduces the experimental results. The 0D model clarifies the physical mechanism of the NBI start-up using pre-ionization described as follows:(1) the seed plasma produces sufficient beam ions immediately after beam injection,(2) the beam ions heat up electrons that promote the ionization/dissociation of the background neutrals,(3) this process acts as a positive feedback loop resulting in further electron heating towards burn-through. The 0D model analysis shows that the critical density corresponds to the state at which the electron heating by the beam ions is equal to electron power loss due to conduction and ionization/dissociation.
环形聚变装置等离子体启动模型分析
DOI：
10.14989/doctor.k19827
发表时间：
2016
期刊：
影响因子：
--
作者：
K. Hada
通讯作者：
K. Hada