HL-2A中环向旋转影响等离子体对共振磁扰动的响应过程

利用MARS-F代码在HL-2A装置下模拟等离子体对共振磁扰动的线性响应过程,研究了等离子体旋转频率对响应的影响.研究发现,扰动场在有理面上的屏蔽效应在旋转频率较大时随旋转增大而增强,但在旋转频率较小时电阻导致的屏蔽效果最强处较有理面的偏移会影响这一规律;扰动场在非有理面上的放大效应主要由芯部扭曲响应引起,且同时与等离子体旋转频率和电阻密切相关.     

EAST托卡马克上共振磁扰动对锯齿行为的影响

锯齿振荡是托卡马克装置上常见的磁流体不稳定性之一.先进实验超导托卡马克(experimental advanced superconducting Tokamak,EAST)装置放电中观察到外加共振磁扰动(resonant magnetic perturbation,RMP)会影响锯齿振荡行为.本文研究了环向模数n=2的RMP对锯齿周期的影响.通过RMP线圈相位差扫描实验发现,当RMP上下线圈(n=2)相位差Δφ_UL发生变化时,扰动场的谱型发生变化,锯齿周期和崩塌幅度也随之发生明显的改变.单流体电阻磁流体力学(MARS-F)程序分析表明,在相同实验条件下,当RMP上下线圈(n=2)相位差为Δφ_UL=270°时,等离子体芯部区域的响应最强,此时锯齿周期和幅度最小.锯齿行为的改变可能与RMP引起的快离子损失相关.该研究利用RMP上下线圈(n=2)实现对锯齿行为的有效调控,有利于未来EAST发展高比压放电条件下的大锯齿自动控制技术.     

托卡马克装置中等离子体环向旋转对三维响应场的影响

本文利用MARS-F程序,数值研究了HL-2M托卡马克装置高比压等离子体中,环向旋转对外加共振磁扰动场的响应特性的影响.研究发现,等离子体响应显著改变共振磁扰动的谱分布,并影响等离子体内部共振磁扰动场与共振磁扰动线圈电流相位差的依赖关系,从而改变有理面处径向扰动场的幅值.当边界旋转频率较小时,在最外有理面处,等离子体响应对外加共振磁扰动场有明显的放大效应.通常,边缘局域模的控制效果依赖于最外有理面处共振磁扰动场的幅度,因此可通过控制旋转剖面实现对共振磁扰动场的调控,进而优化边缘局域模的控制方案.     

等离子体对共振磁扰动的流体和动理学响应的模拟研究

本文利用MARS-F/K程序和解析方法,模拟研究了‘类-DEMO’平衡下等离子体对共振磁扰动的流体响应和动理学响应.研究发现,当新的有理面经过等离子体边缘台基区时,最外层有理面处总径向扰动场b₍res(tot))¹和等离子体边界X点附近扰动位移ξX两个优化参数在特定的q₉₅(95%归一化极向磁通量处的安全因子)窗口出现峰值,峰值的个数y与环向模数n呈正相关,即y≈n?q₉₅(?q₉₅=3.5).上下两组线圈电流相位差的最优/差值与q₉₅之间满足线性依赖关系,可用线性函数进行拟合.线圈电流幅值的优化不改变电流相位差的最优值,但可以增大优化参数ξX.线圈电流幅值的最优值依赖于环向模数n.包含背景粒子和高能粒子动理学效应的结果表明,对于低β(等离子体比压值)等离子体,动理学响应与流体响应保持一致,与有无强平行声波阻尼无关;而对于高β等离子体,在流体响应模型中需要考虑动理学效应的修正作用.考虑强平行声波阻尼(κ_∥=1.5)的流体响应模型能够很...     

EAST共振磁扰动线圈电源响应延迟分析及优化

为了提高EAST装置中共振磁扰动(RMP)线圈电源的输出电压、电流响应速度和输出特性,对共振磁扰动线圈电源的响应时间延迟进行了分析和优化处理。详细分析了对称规则采样和单极性倍频PWM调制过程所产生的时间延迟,针对该部分时间延迟提出了多次采样延时数据更新方法,对逆变电源控制器进行优化和改进。实验结果表明,采用该方法后电源输出响应时间延迟从206μs减小为70μs,可以满足EAST实验的需求。     

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.     

HL-2M等离子体对共振磁扰动线圈电流相位响应的模拟

在HL-2M托卡马克平衡位形(Ip=1.0MA,βN=1.62,q95=4.01)下,使用环形单流体程序MARS-F研究了等离子体对共振磁扰动(RMP)线圈电流相位差的响应.在最优相位差时,扰动磁场显著地改变边界层磁场的拓扑,形成明显的磁岛链,增加了等离子体在边界层的输运,降低了压强梯度,减小了对ELM的驱动.模拟结果...     

HL-2A 共振磁扰动线圈电源的方案设计与仿真

介绍了共振磁扰动(RMP)电源的电路拓扑结构,基本元器件的选取,初步控制方案以及电路相关的计算与仿真。RMP 线圈将由最大4kA 的直流电流或者最大频率1kHz 最大4kA 的交流正弦电流供电。通过选择合理的电源结构和控制方式,以实现响应速度快和电流纹波小的要求,并使RMP 线圈电源满足ELM 控制的需求,尽量降低对等离子体控制的不利影响。     

向列相液晶nCB(4-n-alkyl-4'-cyanobiphenyls,n=5-8)的旋转黏度及其奇偶效应的分子动力学模拟

在全原子力场模型的基础上,对向列液晶nCB(4-n-alkyl-4'-cyano biphenyls,n=5-8)进行了等压等温NPT系综下的分子动力学(MD)模拟.对MD的轨迹分析得到了二阶和四阶序参数以及描述液晶分子翻转运动的取向时间相关函数(TCF),并通过一个近似的单指函数对TCF拟合得到了相关时间.在此基础上,计算了nCB(n=5-8)的旋转扩散系数(Rotat ional diffusion coefficient,RDC).利用基于统计力学模型的Nemtsov-Zakharov方法和Fialkowski方法,分别计算了它们的旋转黏度系数(rotational viscosity coefficient,RVC),进而分别讨论了RVC,RDC和相关时间的奇偶效应.与文献中的实验结果比较表明,该方法得到了合理的计算结果和一致的奇偶效应.     

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.     

Toroidal plasma rotation induced by the dynamic ergodic divertor in the TEXTOR tokamak

The first results of the Dynamic Ergodic Divertor in TEXTOR, when operating in the m/n=3/1 mode configuration, are presented. The deeply penetrating external magnetic field perturbation of this configuration increases the toroidal plasma rotation. Staying below the excitation threshold for the m/n=2/1 tearing mode, this toroidal rotation is always in the direction of the plasma current, even if the toroidal projection of the rotating magnetic field perturbation is in the opposite direction. The observed toroidal rotation direction is consistent with a radial electric field, generated by an enhanced electron transport in the ergodic layers near the resonances of the perturbation. This is an effect different from theoretical predictions, which assume a direct coupling between rotating perturbation and plasma to be the dominant effect of momentum transfer.     

B/N掺杂类直三角石墨烯纳米带器件引起的整流效应

基于密度泛函理论结合非平衡格林函数的方法, 研究了硼(氮)非对称掺杂类直三角石墨烯纳米带器件的电子输运性能. 计算结果表明: 单个硼或氮原子取代类直三角石墨烯纳米带顶点的碳原子后, 增强了体系的电导能力, 并且出现了新颖的整流效应. 分析表明: 这是由于硼氮掺杂类直三角石墨烯纳米带器件在正负偏压下分子能级的移动方向和前线分子轨道空间分布的不对称而产生的. 最重要的是, 当左右类直三角石墨烯纳米带的顶端原子同时被硼和氮掺杂后, 体系的整流效应显著增强, 而且出现负微分电阻效应.     

(GaAs)n(n=1-4)原子链电子输运性质的理论计算

本文利用密度泛函理论结合非平衡格林函数的方法, 对 (GaAs)_n(n=1-4)直线原子链与Au(100)-3×3两半无限电极耦合构成Au-(GaAs)_n-Au纳米结点的电子输运性质进行了第一性原理计算. 在各结点拉伸过程中, 对其结构进行了优化, 得到各结点稳定平衡结构时Ga-As的平均键长分别为0.220, 0.224, 0.223, 0.223 nm, 平衡电导分别为2.328G₀, 1.167G₀, 0.639G₀, 1.237G₀; 通过对结点投影态密度的计算, 发现电子传输主要是通过Ga, As原子中p_x与p_y电子轨道相互作用形成的π键进行的. 在0-2 V的电压范围内, 对于(GaAs)_n(n=1-3)的原子链的电流随电压增大而增大, I-V曲线呈线性关系, 表现出类似金属导电行为; 对于(GaAs)₄原子链在0.6-0.7 V, 0.8-0.9 V的电压范围内却存在负微分电阻现象.     

Magnetic phase transitions in RMnGe (R=Tb, Dy) compounds induced by high magnetic fields

Magnetization isotherms for polycrystalline TbMnGe and DyMnGe compounds were measured at the temperature 4.2 K in pulsed magnetic fields (up to 360 kOe). The received isotherms demonstrate the appearance of metamagnetic transitions at low temperatures. Both compounds crystallize in the orthorhombic TiNiSi-type structure. It was found that the magnetic phase transitions with a destruction of ferrimagnetic spiral structure occur in the TbMnGe and DyMnGe compounds in high magnetic fields. An attempt was undertaken to explain the nature of these transitions using the results of the powder neutron diffraction and the qualitative estimation of the exchange interaction values on the basis of the molecular field theory.     

High-frequency sonoelectrochemical processes: mass transport, thermal and surface effects induced by cavitation in a 500 kHz reactor

The use of high frequency ultrasound in electrochemical systems is of major interest for the optimisation of electrosynthetic and electroanalytical procedures, especially when the strong mechanical effects of 20 kHz ultrasound are detrimental. The characterisation of a 500 kHz ultrasound reactor for sonoelectrochemical experiments by voltammetric and potentiometric measurements revealed the presence of considerable thermal, as well as mass transport, effects depending on geometric parameters and the material used for the construction of the working electrode. Micromixing and cavitation processes govern the mass transport to and from the electrode surface and are shown by atomic force microscopy (AFM) to cause erosion on the electrode surface. Electrochemically active films of Prussian blue are shown to be gradually removed by cavitation erosion. Degassing the solution prior to sonication increases the efficiency of cavitation processes.     

单次飞秒激光脉冲在玻璃内部产生多次微爆的研究

在入射能量不同的情况下，用近红外飞秒激光脉冲在重钡火石玻璃（ZBaF15）内部产生了色心和微爆，在熔融石英的内部产生了多次微爆现象.实验表明：入射能量较高时，色心的中间会产生微爆；在松聚焦条件下，一个飞秒激光脉冲在透明介质内会激发多次微爆.基于飞秒激光脉冲在透明介质内的自聚焦效应和自由电子等离子体的自散焦效应，理论分析了多次微爆产生的原因；也讨论了飞秒激光脉冲诱导玻璃折射率改变的机理.     

SiCl4���������е����Ի������ײ���

设计了一个取样位置能在射频辉光放电等离子体电极间自由移动的取样装置,用质谱计测量了SiCl4等离子体的离子信号。提出了一种线性拟合的方法用于计算SiCl4等离子体的消耗率,利用测量的离子信号,计算出了SiCl4等离子体中SiCln(n=0~2)中性基团的空间分布。实验结果表明,可移动质谱取样装置的设计是合理的;用线性拟合方法得到的等离子体消耗率和中性基团的相对密度,比以前的方法得到的更精确。     

Inverse TMR in a nominally symmetric CoFe/AlOx/CoFe junction induced by interfacial Fe3O4 investigated by STEM-EELS

We have found inverse tunneling magnetoresistance (TMR) with a non-symmetric bias voltage dependence in a nominally symmetric Si (001)/Ag/CoFe/AlO_x/CoFe/IrMn/Ag magnetic tunnel junction after field cooling. The O K edge fine structure extracted from electron energy loss spectroscopy spectrum images taken at the interfaces of junctions with inverse TMR shows a thin, discontinuous Fe₃O₄ layer at the CoFe/AlO_x interfaces. The Fe L_2,3 edge core level shifts are also consistent with those of Fe₃O₄. We find no Fe₃O₄ layer in junctions with normal TMR. We believe this Fe₃O₄ layer is responsible for the inverse TMR.     

The dipole moment of HOCl in vOH=4

Pulsed laser excitation and photofragment detection methods are used to observe the 17_0,17←16_1,16 pure rotational transition within the v_OH=4 vibrational state of HO³⁵Cl. Microwave frequency and Stark effect measurements give ν₀=27484.33(10) MHz and μ_b=1.562(9) D. The dependence of μ_b, which is approximately parallel to the OH bond, on the level of OH stretch excitation appears linear and is consistent with that of H₂O over the same 0-14 000 cm⁻¹ energy range.