Observation of second harmonic electron cyclotron resonance heating and current-drive transition during non-inductive plasma start-up experiment in QUEST
Observation of second harmonic electron cyclotron resonance heating and current-drive transition during non-inductive plasma start-up experiment in QUEST
复制标题
QUEST 无感等离子体启动实验中二次谐波电子回旋共振加热和电流驱动转变的观察
DOI：
10.1088/1361-6587/ac1838
复制
发表时间：
2021
影响因子：
2.2
通讯作者：
O
中科院分区：
文献类型：
--
作者：
Kojima S.;Hanada K.;Idei H.;Onchi T.;Ikezoe R.;Nagashima Y.;Hasegawa M.;Kuroda K.;Nakamura K.;Higashijima A.;Nagata T.;Kawasaki S.;Shimabukuro S.;Elserafy H.;Fukuyama M.;Ejiri A.;Shikama T.;Yoneda N.;Yoneda R.;Kariya T.;Takase Y.;Murakami S.;Bertelli N.;O
Q-shu 大学的稳态球形托卡马克实验演示了使用二次谐波电子回旋共振加热 (ECRH) 和倾斜射频 (RF) 注入来启动非感应等离子体电流。在加热和等离子体电流上升过程中观察到强烈的转变。初始体电子加热状态表现出 T ebulk∼ 140 eV，无硬 X 射线 (HXR) 发射，Ip 低至 ∼ 15 kA；它突然转变为表现出约 10 eV 的低 T ebulk 和约 50 kA 的高 Ip 的强 HXR 发射的状态。这种行为与之前的基本 ECRH 实验中观察到的行为明显不同。考虑波功率吸收和等离子体功率平衡，研究了加热和电流驱动转变的机制。结果表明，转变是由尾部电子的有利加热引起的，其中二次谐波处的射频功率吸收随着 T etail 几乎线性增加，而从尾部电子到体电子的功率传输随着 1/T etail 0.5 降低。这会导致快速过渡到高 T etail 状态，同时将 T ebulk 降低到较冷的离子温度。了解过渡机制有助于考虑使用二次谐波 ECRH 来启动 JT-60 SA 和 ITER 等托卡马克反应堆的等离子体电流。
Noninductive plasma current start-up using 2nd harmonic electron cyclotron resonance heating (ECRH) with oblique radio frequency (RF) injection is demonstrated in a Q-shu University experiment with steady-state spherical tokamak. A strong transition was observed in the heating and plasma current ramp-up. The initial bulk electron heating regime exhibits T ebulk∼ 140 eV and no hard x-ray (HXR) emission with a low I p of∼ 15 kA; it abruptly transitions to a regime that exhibits a low T ebulk of∼ 10 eV and a strong HXR emission with a high I p of∼ 50 kA. This behavior is distinctly different from that observed in previous fundamental ECRH experiments. The mechanism of the heating and current drive transition are investigated considering wave power absorption and plasma power balance. The results indicate that the transition is caused by the favorable heating of tail electrons where the RF power absorption at the 2nd harmonic increases nearly linearly with T etail, while the power transfer from the tail electrons to the bulk electrons decreases with 1/T etail 0.5. This causes a rapid transition to a state with high T etail while reducing T ebulk towards colder ion temperature. The understanding of the transition mechanism helps to consider plasma current start-up using 2nd harmonic ECRH for tokamak reactors such as JT-60 SA and ITER.