潘宁阱中电子等离子体稳态的数值模拟

应用粒子模拟方法研究了电子束潘宁阱中的非中性等离子体的稳定状态及其定标关系，数值模拟结果表明，给定电子的初始分布和外场条件后，潘宁阱中可以出现聚心状态的电子等离子体，中心电子密度可达10倍布里渊密度；电子密度分布与理想的I／r^2关系有差别，阱中的电子数越多，差别越大。系统趋于稳定状态的弛豫时间反比于阱中的电子总数而正比于外加电场强度。     

磁阱中的低温等离子体

本文分析了在一个棒镜线圈组合成的磁阱装置中,当沿着镜场轴线注入电子束,电子束与中性氢分子碰撞电离产生等离子体时,等离子体在该磁阱中的行为,文中也介绍了对这种等离子体进行实验研究的结果。     

基于捕获的新型正电子束及应用

基于捕获的新型正电子束技术是通过潘宁阱中捕获、约束和积累正电子而发展的新一代正电子束技术。本文介绍正电子的捕获、冷却,压缩技术,基于捕获的正电子束形成技术,以及该技术将来发展展望,最后讨论该技术在原子物理学和材料科学等多个领域的应用。     

质子束尾波场中利用密度跃变实现电子捕获及加速的粒子模拟

 用2D3V粒子模拟程序研究了高能质子束驱动的尾波场加速电子的方案,及其在此方案中应用背景等离子体密度的跃变致使等离子体电子自注入加速相区的可能性。粒子模拟结果显示:密度跃变实现了电子的自注入,并且捕获的电子束处于加速相位,等离子体尾波场纵向电场对捕获的电子束起箍缩作用;捕获的电子束随着传输,表现为窄能谱分布;同时随着密度跃变大小的增大,可以增加等离子体电子的捕获。     

相对论电子束虚阴极静电振荡的粒子模拟

本文运用有限大小粒子模型,用等离子体粒子模拟方法,对相对论电子束的虚阴极振荡作了一维静电粒子模拟。结果表明,在注入电流小于空间电荷极限电流时,电子束能稳定传输并能全部通过。当注入电流超过空间电荷极限电流时,传输是不稳定的,将有部分电子反射,部分通过。空间电荷形成的虚阴极的位置和电势周期性地振荡。电流越大,虚阴极位置越靠近注入面且变化范围越小,虚阴极电势越低且振幅越大,振荡频率越高且大于电子束等离子体频率。     

电子束入射改善托卡马克等离子体约束

 分析了电子束入射托卡马克等离子体表面后所发生的一系列物理过程,特别是电子束注入等离子体后在边界层形成平行电流和径向负电场,使等离子体由低约束模式向高约束模式,即L H模式转换中的作用。论证了当注入电子束的密度超过一定的阀值时,L H 模转换被触发。     

电子束产生大尺度等离子体过程的数值模拟研究

建立了一个四组分一维混合模型，对电子束注入大气产生大尺度等离子体的过程进行了数值模拟.结果表明了能量为140keV、流强为50mA/cm²的注入电子束，可以产生线度为0.5m，密度为10¹²cm^-3量级的大气环境下等离子体.电子束所伴随的空间电荷效应由于等离子体的产生会很快消失，不影响后续的等离子体产生过程.电子束注入流强主要影响产生等离子体的密度，而电子束能量则同时影响其空间线度和密度. 关键词： 电子束 碰撞 电离     

In_(0.22)Ga_(0.78)As/GaAs量子阱光致发光谱电子辐照效应研究

对未掺杂的In_(0.22)Ga_(0.78)As/GaAs量子阱材料开展了能量为1 MeV、电子注量达1×1016/cm~2的电子束辐照实验。实验结果显示,电子束轰击量子阱材料,通过能量传递在材料中引入缺陷,导致光致发光减弱;电子束辐照后的量子阱中同时存在应力释放和原子互混现象,导致量子阱的发光峰先红移后蓝移;辐照后的量子阱发光波长取决于应变弛豫和扩散的共同作用。     

充气型放电毛细管的密度测量及磁流体模拟

在激光尾波场电子加速机理中,为了有效地加速电子,需要抑制衍射散焦等造成的激光传输不稳定性问题. 激光脉冲的稳定传输不仅有利于能量耦合给等离子体波,而且对电子束的注入及稳定加速有着重要影响,具有一定横向密度分布的充气型放电毛细管可以有效引导激光脉冲的传输. 利用等离子体的Stark展宽效应对毛细管产生的等离子体进行密度测量,给出了等离子体密度与充气压强之间的关系. 利用磁流体程序CRMHA对毛细管的放电特性进行了模拟,研究了毛细管引导效应的形成机理. 关键词： 充气型放电毛细管 Stark展宽 磁流体模拟 引导     

Compton散射下激光等离子体界面附近电子的运动

研究了多光子非线性Compton散射下等离子体中两个不同密度区的界面附近耦合激光场中电子的运动, 导出了电子的横向动量与纵向动量相互关系的一般方程.研究发现：介质的非均匀性导致电子运动特性的重要变化,在一定的条件下,这种非均匀性有利于注入电子获得加速;散射可有效地降低弹推阈值.当耦合脉冲强度低于弹推阈值时,电子最终被脉冲超过,但无论对初始时刻静止的电子还是运动的电子,能量增益均不为0,且随注入能量的提高而迅速地增加.当耦合脉冲强度高于弹推阈值时,电子最终超过脉冲而获得很高的能量增益,其值远远高于均匀等离子体的情况.在入射相同能量的情况下,耦合光会使电子获得更高的能量增益.     

Induced Resonance Processes Accompanying Interaction of the Field of a TEM Trap with Oscillating Charges

We theoretically analyze resonance processes in an electromagnetic trap (TEM trap) formed by a circularly polarized high-frequency standing field of homogeneous plane waves and a uniform static magnetic field aligned with the direction of wave propagation. The regime of resonance amplification of the trap field by an ensemble of initially nonphased oscillators in the absence of a static magnetic field is described. The regime of resonance acceleration of charges from thermal to relativistic velocities for a bounded particle motion in the presence of a static magnetic field is considered. It is shown that charge oscillations in the trap are similar to flutter in mechanical systems. The efficient energy exchange is stipulated by an M-type interaction mechanism.     

直线感应加速器加速间隙对发射度的影响

文中用解析方法计算了直线感应加速器加速间隙对发射度的影响。考虑了存在轴向引导磁场,加速电场,束流分裂以及多个加速间隙的作用。这种解析方法也适用于射频直线加速器的情形。     

SiOxNy薄膜高场电子陷阱和释放特性的研究

本文研究热氮氧化硅(SiO_xN_y)薄膜在高场下的电子陷阱和被陷电子的释放。发现:当样品被氮化的程度较轻时,膜中的有效电子陷阱表面浓度随着样品被氮化时间的增加而迅速增加,被陷电子的释放率近于零,与样品被短路的时间及外加反向电场的持续时间和大小(直到8MV/cm)无关,电子陷阱能级是较深的;当样品被氮化的程度较重时,随着对样品氮化时间的进一步增加,膜中的有效电子陷阱表面浓度逐渐减小,电子陷阱能级深度逐渐变浅,被陷电子的释放率逐渐增加,并与外加反向电场和外加反向电场的 关键词：     

Investigation of trap states in Al_2O_3 InAlN/GaN metal–oxide–semiconductor high-electron-mobility transistors

In this paper the trapping effects in Al2O3/In0.17Al0.83N/Ga N MOS-HEMT(here, HEMT stands for high electron mobility transistor) are investigated by frequency-dependent capacitance and conductance analysis. The trap states are found at both the Al2O3/In Al N and In Al N/Ga N interface. Trap states in In Al N/Ga N heterostructure are determined to have mixed de-trapping mechanisms, emission, and tunneling. Part of the electrons captured in the trap states are likely to tunnel into the two-dimensional electron gas(2DEG) channel under serious band bending and stronger electric field peak caused by high Al content in the In Al N barrier, which explains the opposite voltage dependence of time constant and relation between the time constant and energy of the trap states.     

Features of Fundamental- and Subharmonics ECR Heating in a Magnetic Trap

We compare the efficiency of microwave heating of electrons in a dense plasma at the fundamental harmonics ( = eH/(mc)) and at the subharmonics ( = eH/(2mc)) of the electron gyrofrequency. In particular, recent experimental results showing a higher efficiency of microwave heating at the frequency equal to one half of the electron gyrofrequency are analyzed. Equations describing the nonlinear subharmonic electron cyclotron resonance (ECR) heating are derived for an arbitrary geometry of the microwave field. If the microwave field has the vacuum polarization, then the microwave power absorbed by electrons at the fundamental harmonic of the electron gyrofrequency in rarefied plasmas exceeds by many orders of magnitude the corresponding power absorbed by electrons in the case of nonlinear heating at one half of the electron gyrofrequency. However, it is shown that this difference in a dense plasma does not exceed one order of magnitude, which is explained by the effect of depression of the resonance component of the microwave field. In this case, the efficiency of the formation of high-energy electron population can be influenced not only by the energy-deposition rate but mainly by the stability condition of an electron in the magnetic trap. It is shown that a twofold decrease in the magnetic field, necessary to satisfy the ECR condition at one half of the electron gyrofrequency, leads to a dramatic shortening of the hot-electron lifetime in a magnetic trap and, in turn, to a dramatic decrease in the energy-deposition efficiency. We discuss the dependence of the electron heating on the effect of quasi-static enhancement of the microwave field near a target located in a magnetic trap for the generation of X-ray emission.     

Manipulation of localized charge states in n-MOSFETs with microwave irradiation

We demonstrate how the charge state of a trap at the Si/SiO₂ interface in a MOSFET can be controlled by microwave irradiation. The device is immersed in a static magnetic field at 300 mK and operates at small bias. Under such experimental conditions the electron spins are almost fully polarized. The electron occupancy of the trap is reversibily raised from one to two electrons by turning on a microwave field of less than 10 μW. Such contactless method controls the charge bound to defects close to the channel and it enables the fast initialization of the charge and spin state of the trapped electrons. This is particularly important in those spin resonance quantum computation schemes where a channel current senses the charge state, to improve the switching clock and to eliminate the related noise.     

Fokker-Planck analysis of energy deposition of laser-produced relativistic electrons in dense plasmas

Evaluation of the energy deposition region of a laser-produced relativistic electron beam in dense core plasma is essential in the fast ignition approach to ICF. Recently, we have developed a two-dimensional relativistic Fokker-Planck code “RFP-2D” for fast electron transport in dense plasmas to investigate the energy deposition profiles. In this paper, we compare the sizes of the energy deposition region derived from RFP-2D and another RFP-type calculation model with stochastic treatments. It is found to be considerably important to take into account the influence of the self-generated electromagnetic field when evaluating the energy deposition region.     

Electrodynamic trap for neutral atoms

An electrodynamic trap is proposed that stores cold neutral atoms or nonpolar molecules in their ground state as well as in excited states by means of the quadratic Stark effect. The trap uses an oscillating hexapole field and a superposed static homogeneous field. The dynamics of an atom in this trap can be described as a harmonic oscillation in a static pseudopotential. Stability criteria and sample parameters for a number of atomic species are given. Received: 7 August 1998 / Received in final form: 7 January 1999     

三氯乙烯氧化硅膜推迟破坏性击穿的机理研究

本文对三氯乙烯(TCE)氧化推迟SiO₂膜的破坏性击穿及其机理进行了研究。结果表明,随着TCE流量的增大、处理时间的增加、温度的升高和氧分压的降低,SiO₂膜的击穿电流耐量增大。但过大的TCE流量和过长的处理时间,将使击穿特性变坏。结果还表明,击穿电流耐量的增大与膜内电子陷阱密度的增大有关。文中提出包括三种恶性循环在内的“低势垒点-电场增强”击穿模型,并考虑氧化气氛中的H₂O对击穿特性的影响,引入电子陷阱抑制低势垒点-电场增强的作用,分析T 关键词：     

量子数n和l对束缚电子径向波函数的影响

利用Hartree-Fork平均自洽场理论,研究了主量子数n和角量子数l对束缚电子波函数影响的主要特征.原子实通常是致密、紧凑的,当n和l较大时价电子的行为将与相应的氢原子电子相似;在靠近核的原子实区域,原子实的影响使价电子径向波函数节点的位置几乎重合.在近核区域离心势可对电子产生很大影响:小l电子只能轻微地贯穿到原子实的较深区域,对大l电子离心势将阻止其深入到离核很近的原子实内;离化度较高时离心势的作用相对减弱,电子深入到原子实内的可能性较大.