基于光弹调制的运动斯塔克效应诊断

电流密度分布是等离子体物理研究的关键分布参数,在托卡马克先进运行模式发展,电流驱动,约束与输运等方面发挥着重要的作用。中性束与等离子体相互作用产生的分裂光谱,包括σ分量与π分量,水平观测时,σ分量的偏振方向垂直于等效电场的方向,π分量的偏振方向平行于等效电场的方向,通过测量分裂光谱的偏振方向可以反演出等离子体电流密度分布。基于光弹调制器的偏振检测系统具有检测精度高、时间响应迅速的独特优点,非常适用于等离子体电流快速变化下的电流密度分布测量。光弹调制器的双折射晶体在周期性外部驱动源的作用下发生弹性形变,其折射率会产生周期性的变化,当偏振光通过时,出射光的偏振特性将相应产生周期性变化,再经过偏振片,形成调制的光强变化。运动斯塔克效应(MSE)诊断的偏振检测系统由两个光弹调制器(PEM)和一个偏振片组成,通过检测不同调制频率的调制强度的比值,从而快速、精确地获得分裂光谱的偏振方向的实时变化,进而得到等离子体电流密度分布。详细介绍了东方超环托卡马克(EAST)装置上的MSE诊断,初步完成了离线测试与标定,参与中性束电流本文驱动物理实验,初步获得了等离子体电流密度分布的信息。     

基于EAST束发射光谱的中性束衰减特征研究

中性束注入(NBI)是托卡马克装置重要的辅助加热与电流驱动手段,中性原子的离化是决定中性束的加热(能量和粒子沉积剖面)和电流驱动效率的关键环节。通常情况下,利用背景等离子体参数与中性束参数模拟计算快的中性粒子与等离子体的离化,即中性束沉积过程,进而分析托卡马克中性束加热和电流驱动效果。束发射光谱是高能中性粒子注入等离子体后,与等离子体的电子、离子发生碰撞激发,中性粒子退激发过程中产生的一系列特征谱线,其束发射光谱强度受等离子体密度、温度、束能量、束密度等因素影响,可以利用束发射光谱强度变化研究中性束的衰减特性。在EAST托卡马克上通过实验测量中性束粒子与等离子体碰撞激发的光谱强度,分析得到了中性束在不同等离子体密度以及不同中性束能量下的衰减特性,并采用主动束光谱仿真与数值分析软件(SOS)进行了相应的模拟计算,研究表明实验测量与模拟计算结果两者具有较好的一致性,这验证了通过实验测量束发射光谱获取中性束衰减特征的可行性。     

自旋轨道矩调控的垂直磁各向异性四态存储器结构

利用氧化钽缓冲层对垂直各向异性钴铂多层膜磁性的影响,构想并验证了一种四态存储器单元.存储器器件包含两个区域,其中一区域的钴铂多层膜[Pt(3 nm)/Co(0.47 nm)/Pt(1.5 nm)]直接生长在热氧化硅衬底上,另一个区域在磁性膜和衬底之间沉积了一层氧化钽作为缓冲层[TaO x(0.3 nm)/Pt(3 nm)/Co(0.47 nm)/Pt(1.5 nm)],缓冲层导致两个区域的垂直磁各向异性不同.在固定的水平磁场下对器件施加与磁场同向的电流,由于电流引起的自旋轨道耦合力矩,两个区域的磁化取向均会发生翻转,且拥有不同的临界翻转电流.改变通过器件导电通道的电流脉冲形式,器件的磁化状态可以在4个态之间切换.本文器件的结构为设计自旋轨道矩存储器件提供了新的思路.     

RF magnetron sputtering induced the perpendicular magnetic anisotropy modification in Pt/Co based multilayers

We demonstrate that radio frequency(RF)magnetron sputtering technique can modify the perpendicular magnetic anisotropy(PMA)of Pt/Co/normal metal(NM)thin films.Influence of ion irradiation during RF magnetron sputtering should not be neglected and it can weaken PMA of the deposited magnetic films.The magnitude of this influence can be controlled by tuning RF magnetron sputtering deposition conditions and the upper NM layer thickness.According to the stopping and range of ions in matter(SRIM)simulation results,defects such as displacement atoms and vacancies in the deposited film will increase after the RF magnetron sputtering,which can account for the weakness of PMA.The amplitude changes of the Hall resistance and the threshold current intensity of spin orbit torque(SOT)induced magnetization switching also can be modified.Our study could be useful for controlling magnetic properties of PMA films and designing new type of SOT-based spintronic devices.     

Bismuth-content-dependent polarized Raman spectrum of InPBi alloy

We systematically investigate the optical properties of the InP_(1-x)Bi_x ternary alloys with 0≤x≤2.46%,by using high resolution polarized Raman scattering measurement.Both InP-like and InBi-like optical vibration modes(LO) are identified in all the samples,suggesting that most of the Bi-atoms are incorporated into the lattice sites to substitute Patoms.And the intensity of the InBi-like Raman mode is positively proportional to the Bi-content.Linear red-shift of the InP-like longitudinal optical vibration mode is observed to be 1.1 cm~(-1)/Bi%,while that of the InP-like optical vibration overtone(2LO) is nearly doubled.In addition,through comparing the(XX) and Z(XY) Raman spectra,longitudinaloptical-plasmon-coupled(LOPC) modes are identified in all the samples,and their intensities are found to be proportional to the electron concentrations.