Mr Xiaoquan JI (China)
Scaling laws for the prediction of neoclassical tearing modes (NTMs) onset in next generation fusion devices such as ITER have been carried out. However, it is difficult to extrapolate current island width thresholds for the NTM onset to ITER due to the uncertainty physics behind the threshold mechanisms. And some events can also influence the mode onset, such as the large sawtooth period and pellet injection. In the HL-2A tokamak, NTMs driven unstable by the transient perturbation of local electron temperature induced by non-local transport (NLT) phenomenon have been observed in low beta plasmas for the first time. In HL-2A, the onset of m/n=3/2 NTMs during NLT phenomenon induced by supersonic molecular beam injection (SMBI) has been observed in low beta plasmas with electron cyclotron resonance heating (ECRH). The inversion surface of electron temperature perturbation (δTe) due to NLT effect is near the q=3/2 surface, which is determined by the peak of 3/2 mode amplitudes measured by the ECE diagnostics. Compared with 3/2 NTMs triggered by sawtooth activities in HL-2A, the transient perturbation of local Te gradient induced by non-local effect plays a crucial role on changing NTM threshold, which dramatically reduces the critical βonset of 3/2 NTMs. In spontaneous 3/2 NTMs without detected core and edge MHD instabilities are observed during strong NLT effect. After the onset of NTM during NLT phenomenon induced by SMBI, additional molecular beam pulses are injected to study the interaction of magnetic islands with NLT effect. The non-local effect still exists with the small 3/2 island, island width w3/2/a~0.06. In the case of large 2/1 magnetic islands, w2/1/a~0.15, the effect of NLT is almost suppressed. By the way, the collapse of the central electron temperature with an increase in the edge electron temperature is observed.
|Country or International Organisation||China|
Mr Xiaoquan JI (China)
Prof. Baoshan Yuan (Southwestern Institute of Physics) Prof. Beibin Feng (Southwestern Institute of Physics) Dr Lai Wei (Dalian University of Technology) Min Jiang (Southwestern Institute of Physics) Prof. Qingwei Yang (Southwestern Institute of Physics) Mr Tengfei Sun (Southwestern Institute of Physics) Dr Wei Deng (Southwestern Institute of Physics) Prof. Yi Liu (southwestern institute of physics) Ms Yuan Xu (Southwestern Institute of Physics) Dr Yunbo Dong (Southwestern Institute of Physics) Dr Zhongbing Shi (Southwestern Institute of Physics) Prof. zhengxiong wang (Dalian University of Technology)