Study of seed plasma generation for NBI plasma start-up using non-resonant microwave launch in Heliotron J
Study of seed plasma generation for NBI plasma start-up using non-resonant microwave launch in Heliotron J
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利用 Heliotron J 中的非谐振微波发射产生 NBI 等离子体启动种子等离子体的研究
DOI：
10.1088/1361-6587/ab877e
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
K Toi and Y Suzuki
中科院分区：
文献类型：
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作者：
S Kobayashi;K Nagasaki;T Stange;T Mizuuchi;H Okada;T Minami;S Kado;S Yamamoto;S Ohshima;K Hada;G Weir;S Konoshima;Y Nakamura;N Kenmochi;Y Otani;X X Lu;A Panith;K Toi and Y Suzuki
本文报道了在Heliotron J装置上利用2.45 GHz微波非共振加热产生种子等离子体的研究结果，该研究结果可用于在低束流功率（< 1 MW）、低加速电压（< 30 kV）和小器件尺寸（≤ 1 m）条件下的中性束注入（NBI）等离子体启动。使用非共振加热的预电离技术产生的电子密度在10 17-10 18 m− 3的数量级，能量超过CII电离势（30 eV）。相对论电子的存在，这是必不可少的产生种子等离子体，实验证实在预电离阶段的同步辐射和硬x射线发射测量。相对论电子的产生机制被认为是电子与微波频率场之间的随机相互作用。通过优化微波发射过程中的附加气体燃料，获得了超过4× 1018 m− 3的更高的种子等离子体密度，从而即使在低NBI功率（0.3 MW）条件下，NBI开启后的快速密度演化也是成功的。采用预电离方法产生的种子等离子体可用于实现W7-X中垂直NBI或LHD中氘NBI等大型日光/仿星器装置在低吸收功率条件下的等离子体启动。
Here, we report on a study of seed plasmas produced by non-resonant 2.45 GHz microwave heating in Heliotron J, which is useful for plasma start-up by neutral beam injection (NBI) under the conditions of low beam power (< 1 MW), low accerelation voltage (< 30 kV) and small device size (∼ 1 m). The pre-ionization technique using the non-resonant heating produced the electron density in the order of 10 17–10 18 m− 3 with the energy exceeds the CII ionization potential (30 eV). The existence of the relativistic electrons, which was essential to produce the seed plasmas, was confirmed experimentally during the pre-ionization phase by the synchrotron radiation and the hard x-ray emission measurements. The production mechanism of the relativistic electrons was considered to be stochastic interactions between the electrons and the microwave-frequency field. By optimizing the additional gas fueling during the microwave launch, a higher seed-plasma density more than 4× 10 18 m− 3 was obtained, resulting that a rapid density evolution after NBI turn-on was successful even in the low NBI power (0.3 MW) condition. The seed plasmas produced by the pre-ionization method is useful to realize the plasma start-up under low absorption power condition in larger heliotron/stellarator devices such as perpendicular NBI in W7-X or deuterium NBI in LHD.