HT-7托卡马克大功率低混杂波电流驱动的实验研究

在HT-7超导托卡马克成功进行了大功率（P_LHW=100—800 kW,f=2.45 GHz）低混杂波电流驱动实验.研究了不同入射功率和等离子体密度下的低混杂波电流驱动效率.获得了以平均电子密度增加、氘阿尔法（D_α）线辐射减少为特征的粒子约束改善;粒子约束时间τ_p增加了约1.5倍.仔细研究了能量约束时间与等离子体密度和低混杂波功率的关系. 关键词： 托卡马克 低混杂波 约束改善 电流驱动效率     

HT-7低杂波电流驱动效率与有效电荷数及电子温度的关系

在HT-7超导托卡马克中进行了低杂波电流驱动的功率扫描实验,功率变化范围为100kW至700kW,频率为2.45GHz。研究了等离子体平均有效电荷数及电子温度与低杂波功率之间的关系。给出了不同功率下低杂波电流驱动效率与有效电荷数及电子温度之间的关系:HT-7装置低杂波驱动效率与电子温度成正比,与有效电荷数成反比。指出了动态杂质控制是改善低杂波电流驱动效率的关键问题。     

低杂波控制电流分布与改善约束研究

在HT-7超导托卡马克装置上利用低杂波电流驱动有效地控制了等离子体电流分布,并使等离子体约束性能改善。数值模拟与硬X射线测量结果均表明,低杂波的发射功率谱、纵场和等离子体密度对改变等离子体电流分布有明显的影响。在优化低杂波电流驱动实验参数的条件下,等离子体密度、温度分布发生了理想的变化。在电子和离子温度分布上出现了内部输运垒,同时等离子体的能量约束时间和粒子约束时间均有提高。     

HT-7低杂波电流驱动效率与有效电荷数及电子温度的关系

在HT-7超导托卡马克中进行了低杂波电流驱动的功率扫描实验,功率变化范围为100 kW至700 kW,频率为2.45 GHz。研究了等离子体平均有效电荷数及电子温度与低杂波功率之间的关系。给出了不同功率下低杂波电流驱动效率与有效电荷数及电子温度之间的关系：HT-7装置低杂波驱动效率与电子温度成正比,与有效电荷数成反比。指出了动态杂质控制是改善低杂波电流驱动效率的关键问题。     

HT-7װ�õ��Ӳ������������ݵ�����Ϊ����

用NaI闪烁体探测器组成的逃逸电子诊断系统和CdTe半导体探测阵列组成的快电子轫致辐射诊断系统,研究了一定等离子体密度条件下低杂波功率和等离子体电流对逃逸产生的影响以及一定低杂波功率下等离子体密度对逃逸电子产生的不同作用效果。根据实验数据计算了HT-7装置等离子体中电子逃逸的阈值电场和一定放电条件下电子逃逸的阈值能量。     

EASTװ�õ��Ӳ���������Ч�ʷ���

在EAST上通过分析剩余环电压与低杂波功率之间的关系,计算得到了低杂波电流驱动效率。采用归一化功率,即功率对等离子体电流、电子密度、等离子体大半径以及有效电荷数归一化,将所有数据绘制在同一曲线中,这样可以得到不同等离子体参数下的低杂波电流驱动效率。实验得到低杂波电流驱动效率η0=(0.5~1.3)×1019 A.m-2.W-1,在等离子体电流Ip=277kA、低杂波功率PLH=681kW条件下,实验得到长达3s的低杂波全波驱动。     

EAST装置低杂波电流驱动效率分析

在EAST上通过分析剩余环电压与低杂波功率之间的关系,计算得到了低杂波电流驱动效率。采用归一化功率,即功率对等离子体电流、电子密度、等离子体大半径以及有效电荷数归一化,将所有数据绘制在同一曲线中,这样可以得到不同等离子体参数下的低杂波电流驱动效率。实验得到低杂波电流驱动效率η₀=(0.5~1.3)×10¹⁹ A.m^-2.W^-1,在等离子体电流I_p=277kA、低杂波功率P_LH=681kW条件下,实验得到长达3s的低杂波全波驱动。     

东方超环上低杂波驱动等离子体环向旋转实验研究

旋转和旋转剪切能抑制磁流体不稳定性和增强等离子体约束.低杂波电流驱动作为未来聚变堆上可能的旋转驱动手段,探索低杂波在现有托卡马克装置上驱动等离子体旋转的驱动机制,可以为未来的聚变堆上旋转预测提供重要参考.在东方超环托卡马克装置上,早期发现了2.45 GHz的低杂波能有效驱动等离子体旋转的现象,认为是边界旋转的改变导致芯部旋转的同电流方向的增加造成的.更高频率下4.6 GHz低杂波电流驱动可以更有效地驱动同电流方向的等离子体旋转.本论文分析在欧姆背景等离子体下,不同功率的低杂波对等离子体环向旋转的影响,研究安全因子剖面变化对环向旋转的关系,利用功率调制获得了低杂波驱动旋转实验中的环向动量输运系数变化情况,发现环向动量扩散系数(χφ)、环向动量箍缩系数(Vpinch)的数值大小趋势是从芯部向靠外的区域逐渐变大.这与低杂波驱动环向旋转时,环向旋转速度由靠外的区域向芯部传递的特性吻合.     

Investigation of lower hybrid current drive during H-mode in EAST tokamak

H-mode discharges with lower hybrid current drive (LHCD) alone are achieved in EAST divertor plasma over a wide parameter range. These H-mode discharges are characterized by a sudden drop in D_α emission and a spontaneous rise in main plasma density. Good lower hybrid (LH) coupling during H-mode is obtained by putting the plasma close to the antenna and by injecting D₂ gas from a pipe near the grill mouse. The analysis of lower hybrid current drive properties shows that the LH deposition profile shifts off axis during H-mode, and current drive (CD) efficiency decreases due to the increase in density. Modeling results of H-mode discharges with a general ray tracing code GENRAY are reported.     

AC operation and runaway electron behaviour in HT-7 tokamak

Operation of HT-7 tokamak in a multicycle alternating square wave plasma current regime is reported. A set of AC operation experiments, including LHW heating to enhance plasma ionization during the current transition and current sustainment, is described. The behaviour of runaway electrons is analysed by four HXR detectors tangentially viewing the plasma in the equatorial plane, within energy ranges 0.3--1.2~MeV and 0.3--7~MeV, separately. High energy runaway electrons (\sim MeV) are found to circulate predominantly in the opposite direction to the plasma current, while the number of low energy runaway electrons (\sim tens to hundreds of keV) circulating along the plasma current is comparable to that in the direction opposite to the plasma current. AC operation with lower hybrid current drive (LHCD) is observed to have an additional benefit of suppressing the runaway electrons if the drop of the loop voltage is large enough.     

HT-7托卡马克上低杂波电流驱动实验中的快电子动力学

在低杂波电流驱动实验中，快电子的动力学对等离子体的品质有至关重要的影响。HT-7托卡马克上，新近发展了一套硬X射线阵列诊断系统用于快电子的动力学研究。本文给出了在不同的低杂波电流驱动实验中，例如高参数，长脉冲，以及反向电流驱动实验，快电子的动力学行为。     

Toroidal rotation induced by 4.6 GHz lower hybrid current drive on EAST tokamak

Using a tangentially viewing x-ray imaging crystal spectrometer, substantial co-current rotation driven by lower hybrid current drive(LHCD) at 4.6 GHz is observed on EAST tokamak. This study presents plasma rotation behaviors with 4.6 GHz LHCD injection. Typically, the 10-20 km/s co-current rotation change and the transport of rotation velocity from edge to core are observed. The relationship between plasma parameters and rotation is also investigated, indicating that rotation decreases with increasing internal inductance(l_i) and increases with increasing safety factor(q_0). Hysteresis between rotation and T_e plasma stored energy is observed, suggesting different response times between the electron heating and rotation acceleration by LHCD. A comparison between the rotations driven by 4.6 G LHCD and 2.45 G LHCD on EAST is also presented, in which higher frequency LHCD could induce more rotation changes.     

CFETR低杂波电流驱动数值模拟研究

利用射线追踪和福克-普朗克方程,研究了CFETR上驱动电流和功率沉积对低杂波注入位置和耦合波谱的依赖关系,讨论了边界非线性效应对电流驱动与功率沉积的影响,给出了低杂波平行折射率和低杂波注入位置的一个优化值。初步数值计算表明：边界非线性效应会导致驱动电流降低;不考虑低杂波非线性效应时,驱动电流的差异约为6%左右,小于考虑该效应时的差异(~25%)。     

Improved lower hybrid current drive efficiency with IBW heating in the HT-7 tokamak

Lower hybrid current drive (LHCD) efficiency in the HT-7 tokamak is observed to increase about 30% with ion Bernstein wave (IBW) heating. The current drive efficiency as high as has been reached in HT-7 thanks to an LHCD/IBW synergy. The IBWs are significantly coupled to the fast electrons produced by the lower hybrid waves, thus results in higher fast electron photon temperature in the combined LHCD + IBW scenario. The interaction of LHCD + IBW improved current drive efficiency.     

Hot electrical conductivity in lower hybrid current drive plasmas in the HT-7 tokamak

The interaction between the hot electrical conductivity and the residual electric field have been investigated in lower hybrid current drive (LHCD) experiments with non-zero loop voltage in the HT-7 tokamak. It has been found that the hot electrical conductivity contribute significantly to the current drive in partial non-inductively sustained plasmas. The hot electrical conductivities under different lower hybrid power levels and different parallel refractive indexes have been obtained. It is comparable to the Spitzer conductivity in high power LHCD experiments.     

托卡马克高场侧低杂波电流驱动模拟研究

利用GENRAY/CQL3D程序研究了EAST装置双零位形下高场侧和低场侧发射低杂波的电流驱动情况.模拟发现,电子密度较小时,高场侧低杂波电流驱动效果不如低场侧.随着电子密度的增加,高场侧低杂波电流驱动的优势逐渐显现,从高场侧发射的低杂波可以将能量沉积在更加靠近等离子体中心的位置.提高环向磁场强度有利于低杂波在高密度条...     

Sawtooth-like electron density oscillations under laser blow-off and lower hybrid current drive in HL-1M tokamak

By using of a six-channel HCN laser interferometer, the sawtooth-like density oscillations without being exhibited in the ohmic phase plasma have been observed during lower hybrid current drive (LHCD) discharges in the HL-1M device. There are often accompanied by injected impurity with laser blow-off. Analyses show that this kind of density sawtooth-like oscillation comes from the mutual effect of LHCD and impurity. An available mechanism is the loss of superthermal electrons by the magnetic perturbation, which is caused by the crash of the central accumulated impurities.     

Optimized calculation of the synergy conditions between electron cyclotron current drive and lower hybrid current drive on EAST

The optimized synergy conditions between electron cyclotron current drive(ECCD) and lower hybrid current drive(LHCD) with normal parameters of the EAST tokamak are studied by using the C3PO/LUKE code based on the understanding of the synergy mechanisms so as to obtain a higher synergistic current and provide theoretical reference for the synergistic effect in the EAST experiment. The dependences of the synergistic effect on the parameters of two waves(lower hybrid wave(LHW) and electron cyclotron wave(ECW)), including the radial position of the power deposition, the power value of the LH and EC waves, and the parallel refractive indices of the LHW(N) are presented and discussed.     

Effects of trapped electrons on off-axis lower hybrid current drive in tokamaks

The effects of trapped electrons on off-axis lower hybrid current drive （LHCD） in tokamaks are studied, A computer code for solving the Fokker-Planck equation in a toroidal geometry is developed and employed. The code is suitable for various auxiliary heating and current drive schemes in tokamak plasmas. The influence of the resonance regime on the current drive efficiency as well as the influence of trapped particle fraction on the current drive efficiency are emphasized. It is shown that, as an electrostatic force, the lower hybrid wave causes some of the trapped electrons to be untrapped and lose their energy, which can cut the LHCD efficiency by about 30%. The ITER scaling law is also used to estimate the trapped electron effects.[第一段]     

EAST������λ��Ե��Ӳ����ʳ���������������Ӱ��

利用MEC和LSC耦合的程序研究了EAST天线不同的相位差 对功率谱的影响及对功率沉积位置和电流分布的影响。通过计算发现,随着 的增大,功率谱的结构发生了改变,当 >200°后功率沉积和电流密度分布由原先的向外层移动变为向内层移动; =200°时形成一个离轴最远的驱动电流, =120°、 =260°时分别得到电流强度最小和最大的驱动电流。因此可以通过选取合适的天线相位差 ,实现对低杂波功率沉积和驱动电流剖面的控制。