HT-7装置上充气对低杂波耦合影响的实验及分析

在低杂波（LHW）天线端口充D₂和CD₄,发现LHW的耦合效果能得到明显改善,充气后LHW的反射系数基本降为6%左右。不同窗口充气对波的耦合和等离子体密度的影响不同,其原因是改善耦合的关键是提高刮削层（SOL）内等离子体的密度。D₂与CH₄对LHW耦合影响的实验结果表明：D₂对LHW的耦合效果影响略好于CH₄,但D₂对等离子体密度的影响明显高于CH₄,原因是D₂对电子密度的贡献更大。     

Development and Preliminary Commissioning Results of a Long Pulse 140 GHz ECRH System on EAST Tokamak(Invited)

A long pulse electron cyclotron resonance heating(ECRH)system has been developed to meet the requirements of steady-state operation for the EAST superconducting tokamak,and the first EC wave was successfully injected into plasma during the 2015 spring campaign.The system is mainly composed of four 140 GHz gyrotron systems,4 ITER-Like transmission lines,4 independent channel launchers and corresponding power supplies,a water cooling,control &inter-lock system etc.Each gyrotron is expected to deliver a maximum power of 1 MW and be operated at 100-1000 s pulse lengths.The No.1 and No.2 gyrotron systems have been installed.In the initial commissioning,a series of parameters of 1 MW 1 s,900 k W 10 s,800 k W 95 s and650 k W 753 s have been demonstrated successfully on the No.1 gyrotron system based on calorimetric dummy load measurements.Significant plasma heating and MHD instability suppression effects were observed in EAST experiments.In addition,high confinement(H-mode)discharges triggered by ECRH were obtained.     

Study of Inverted Sawtooth Activities in EAST Plasma

On the EAST tokamak, during whole off-axis LHCD （low hybrid current drive） limiter discharge, inverted sawteeth oscillations on the SXR （soft X-ray camera） signals appear continuously, and no positive sawtooth is observed. It is thought that this phenomenon is caused by the curvature pinch, though it could partly be explained by the electron temperature profile observed on the PHA （soft X-ray pulse height analyzer） system. The off-axis LHCD and Ohmic heating generate a non-monotonic q profile. According to the curvature pinch effect, this q profile leads to a special electron density profile that has a valley ring. The non-monotonic q profile and the special electron density profile lead to this interesting phenomenon.     

Evaluation of electron cyclotron current drive performance for CFETR

A number of simulations of electron cyclotron current drive (ECCD) have been carried out for the China Fusion Engineering Test Reactor (CFETR) using the C3PO/LUKE code to investigate the performance and optimize schemes of power injection for the design of the launcher. The operation ranges of the toroidal field, cutoff density, and resonance layer location are given at different source frequencies in CFETR phases I and II. A comparison of ECCD performance between the horizontal and top port launch is presented. ECCD efficiency (r_EC) estimated for CFETR phase I isr_EC=0.21 for top port launch andr_EC=0.20 for horizontal port launch. The ECCD efficiency and second-harmonic absorption is calculated at different wave frequencies (from 170 to 230 GHz) in CFETR phase II. It is found that the highest driven efficiency is obtained at 210 GHz with the toroidal field of 6.5 T, and the second-harmonic absorption increases rapidly with the increase of frequency.     

EAST电子回旋波与低杂波双波协同的数值模拟

为在EAST装置中优化电子回旋波与低杂波双波协同的电流驱动效率，从而获得更大的协同驱动电流以维持长脉冲运行，本文以双波协同驱动电流的物理机制为基础，运用模拟程序C3PO/LUKE对EAST参数下电子回旋电流驱动与低杂波电流驱动的协同效果进行了数值模拟计算，给出了协同电流和协同因子。计算结果表明：当两波驱动电流密度峰值的位置一致时协同效果最佳；而电子密度和电子温度的增加可能导致两波重叠区域的变化进而影响协同效果。     

Experimental Investigation of Lower Hybrid Wave Coupling in HT-7

Experiments on lower hybrid wave(LHW)coupling were investigated in the HT-7 tokamak.Good coupling of LHW plasma has been demonstrated at different conditions in the HT-7 tokamak.Relevant results have proved that LHW-plasma coupling is affected by the phase difference between adjacent waveguides.Furthermore,the edge density around the grill and relevant coupling can be adjusted by changing the plasma line average density or the gap value between the LH grill and the last closed flux surfaces(LCFS).It is found that the coupling of LHWs becomes poor when the edge density around the LH grill is large enough in the HT-7tokamak,and that coupling remains good with a proper edge density.With increasing LHW power,it is also found that the reflection coefficients(RCs)increase due to non-linear effects under conditions of low edge recycling,but can decrease under high edge recycling.The edge density depends mainly on the competition between the ponderomotive force(PMF)and the edge recycling intensity in the HT-7 tokamak.     

Blob properties in I-mode and ELM-free H-mode compared to L-mode on EAST

The blob properties in I-mode and ELM-free H-mode plasmas compared to L-mode have been investigated on the EAST tokamak, including the blob detection rate N_b,size δ_b,lifetime τ_b and radial velocity v_r,b.The blob properties in L-mode and I-mode are similar, and those in ELM-free H-mode are different to them. The blob Nbis smaller while τbis larger in H-mode. The experimental blob sizeδband velocity scalings v_r,b-δ_b show a good agre...     

Investigation of LHCD Efficiency and Transformer Recharging in the EAST Tokamak

The efficiency of lower hybrid current drive(LHCD) for limiter and divertor configurations in the EAST tokamak is investigated using hot electrical conductivity theory and experimental formulas.The results indicate that the efficiency of current drive in divertor geometry is slightly higher than that in limiter one.To interpret the experimental results,the GENRAY code is applied to calculate the propagation and absorption of the lower hybrid wave(LHW) in different configurations.The numerical results show that the variation in the parallel refractive index(N//) between the two configurations is quite large.Transformer recharging experiments were also successfully conducted in EAST.By means of the Karney-Fisch method,the absorption index(α) and the upshift factor of refraction(β) for the LHW are obtained.In addition,the maximum recharging efficiency in EAST is about 4% in the divertor configuration,with a line-averaged electron density of n e av = 0.7 × 10 19 m 3.