超冷等离子体演化早期的离子温度与库仑耦合强度

利用开发的磁光阱-离子速度成像装置，实验测量超冷等离子体的离子温度与库仑耦合参数。同时利用带电粒子追踪数值方法模拟超冷等离子体的早期演化过程。实验和模拟结果表明：在超冷等离子体演化早期，无序诱导加热机制导致离子温度快速上升，而库仑耦合强度下降至2.5。进一步研究还发现：在离子非平衡演化阶段，等离子体膨胀速度会快速接近并超过离子热速度，因此离子达到局域热平衡之后的库仑耦合参数会高于测量值。     

HL-1装置离子温度的电荷交换法测定

本文叙述了用自己研制的六道中性粒子分析器(即中性粒子谱仪),测量HL-1托卡马克装置离子温度的实验,给出了在1986年进行的一组放电实验所得等离子体的离子温度及其随放电时间变化的结果,测得的中心离子温度的典型值为474eV,在相应等离子体参数下,Artsimovich经验公式给出450eV     

HL—1M装置等离子体离子温度测量

在ＨＬ－１Ｍ托卡马克装置上，利用８通道中性粒子能谱仪测量的等离子体离子温度。在等离子体电流和密变化、激光吹气、弹丸注入，超声分子束注入和低混杂波加热等实验条件下，观测了Ｔｉ的变化。     

在HL－1M装置上用弯晶谱仪测量离子温度

本文叙述在ＨＬ－１Ｍ装置上用弯晶谱仪获取Ｆｅ的类Ｈｅ离子谱，用谱线的多谱勒加宽测量等离子体的离子温度，得到的等离子体ＨＬ－１Ｍ装置离子温度为５００—８００ｅＶ。     

高频加热磁镜装置等离子体离子能量分布的测量

利用圆柱形低能离子静电分析器,对穿过高频加热磁镜装置逸出锥的逃逸离子和电荷交换生成的中性粒子的能量进行了测量,得到了等离子体离子的能量分布、离子回旋共振条件、以及发生离子回族共振时等离子体离子平均温度与加热净功率之间的线性关系。当加热净功率为100kW时,等离子体离子平均温度约为45eV。每1kW加热净功率大约提高离子温度0.4eV。     

振镜法测量等离子体离子温度

 离子温度是托卡马克等离子体一个重要参数，介绍了一套振镜扫描装置，该装置主要由0.5m单色仪和安装在出射狭缝前的振动的石英镜片组成，时间分辨率小于10ms，系统测量误差小于20eV。测量了HT-6M托卡马克CV(227.1nm)谱线的线形，并由谱线的多普勒展宽得出欧姆加热和离子回旋共振加热（ICRH）下的离子温度，结果表明ICRH期间离子温度由200eV升高到300eV。这套装置广泛应用在中小型托卡马克上。     

离子灵敏探针及其在磁镜装置中的应用

使用离子灵敏探针(ISP)对MM-2U简单磁镜装置中等离子体的离子温度和电子温度进行了测量。描述了这种静电离子探针的工作原理及主要的设计参数。对从探针特性曲线得到的离子温度及密度也予以讨论。     

普林斯顿托卡马克如何创造了等离子体离子温度的世界纪录

在美国普林斯顿实验室,建有一个大的托卡马克,名字为TFTR装置.1986年6月在这个装置上的等离子体得到了很好的约束,称之为“提高型约束”.引人注目的是在这种约束状态下,等离子体的离子温度达到了20 KeV(略大于2亿K).这是托卡马克等离子体离子温度的最新世界纪录. TFTR装置的主要参数如下:大半径2.5m,小半径0.45-0.9m,最大环形磁场5.2T.这台装置是在1982年开始运行的.原计划是首先达到点火的水平,然后在八十年代末以氘-氚运行,在能量自持的情况下,希望有小量的正功率输出.对于氘-氚反应,能量自持要求下面两个条件:(1)很高的离子温度,要…     

红外激光和远红外激光的汤姆逊散射

在受控热核反应的研究中,等离子体的离子温度是实现受控“点火”的一个极重要的参数.应用红宝石激光的汤姆逊散射可以正确地测量等离子体的电子温度和电子密度.但要用来测量离子温度的话,则由于散射角太小,杂散光太大,在技术上变得非常困难.只有应用电荷交换的中性粒子能谱分析的方法才可以测量离子温度.可是,在较高的粒子密度或等离子体装置较大的情况下,由于等离子体的线度大于中性粒子的平均自由程,这种方法也就无法测量等离子体内部的离子温度.如果使用光谱分析的方法,由于存在杂质辐射,在技术上是很困难的.并且分辨率很差.因此,迄今为…     

离子能量分析器测量特性的仿真研究

针对空间等离子体及其模拟环境、空间原子氧及其模拟环境对离子能谱测量的需要，利用仿真软件COMSOL，对离子能量分析器的低能离子测量特性进行了仿真研究。介绍了离子能量分析器的工作原理，对离子能谱测量过程进行了公式推导。通过对三种待选仪器设计方案进行离子透过率仿真分析，确定了一种较优的仪器设计方案。多种离子温度下的误差分析结果也表明，该设计方案能够较为准确地测量离子能量分布。分析了电场畸变、等离子鞘层、栅网对齐方式和离子温度对测量结果的影响，根据仿真结果对一些仿真实验现象做出了合理的解释。     

Nonlinear-Ion-Acoustic-Wave Instability, Threshold, Half Width of Trapped Region and Transition Region

Nonlinear Landau damping of ion acoustic wave (IAW) is one of the most important phenomena in the ionosphere and in space and laboratory plasma as well. The instability growth rate of the IAW with electron drift, the amplitude threshold for exciting the nonlinear effects, the half widths of the trapped region with the trapped electrons are studied experimentally. Under the experimental conditions, it is shown that there is a frequency range of 140--160 kHz, within which the growth rate has the largest value of about 6×10⁴--1.5×10⁵ s^-1. We obtain the transitional region width caused by collisions theoretically and experimentally, for the first time to our knowledge. The experimental results are in good agreement with the theoretical prediction.     

Reduction of stimulated brillouin scattering by the generation of ion acoustic harmonics

Ion wave harmonics generated by the primary ion acoustic wave excited in stimulated Brillouin scattering are shown to introduce heavy nonlinear damping of the process and to considerably reduce the anomalous reflectivity in an underdense plasma (n/n_c<0.5). The generation of ion wave harmonics acts similarly to strong linear damping and provides an alternative explanation to the heavy damping indicated by experiments.     

Effect of a high-frequency field on the reflection of ion acousticwaves from the sheath at a grid

Experiments are described which show that the reflection coefficient for ion acoustic waves (IAW) from the sheath at a grid is affected by an HF electric field with a frequency f_HF≲5f_pi(f_pi =ion plasma frequency). For peak-to-peak amplitudes of the HF voltage drop across the sheath Φ₀≲k_B T_e/e and f_HF>f _pi, the energy distribution of the ions passing through the grid develops a hot tail and the reflected wave suffers enhanced Landau damping. If Φ₀≳k_BT_e/e and f_HF<f_pi, a large-amplitude IAW is excited at the grid; a well-defined ion beam is formed; and local growth of the reflected wave is observed. Test waves launched from the grid show the same propagation characteristics as the reflected waves     

离子与尘埃相互作用对离子声波和尘埃声波的影响

基于流体力学方程和与时间相关的线性微扰理论，分析了尘埃等离子体环境中离子与尘埃粒子的相互作用对离子声波和尘埃声波的影响，结果表明两者间的相互作用使得离子声波变得稳定而使尘埃声波变得不稳定。     

Exact solution for the generalized Bohm criterion in a two-ion-species plasma

For a weakly collisional two-ion species plasma, it is shown that the minimum phase velocity of ion acoustic waves (IAWs) at the sheath-presheath boundary is equal to twice the phase velocity in the bulk plasma. This condition provides a theoretical basis for the experimental results that each ion species leaves the plasma with a drift velocity equal to the IAW phase velocity in the bulk plasma [D. Lee et al., Appl. Phys. Lett. 91, 041505 (2007)10.1063/1.2760149]. It is shown that this result is a consequence of the generalized Bohm criterion and fluid expressions for the IAW phase velocities.     

Dynamical behaviour of non-linear quantum ion acoustic wave in weakly magnetized electron–positron–ion plasma

In order to investigate the propagation characteristics of linear and non-linear ion acoustic waves (IAWs) in electron–positron–ion quantum plasma in the presence of external weak magnetic field, we have used a quantum hydrodynamic model, and degenerate statistics for the electrons and positrons are taken into account. It is found that the linear dispersion relation of the IAW was modified by the externally applied magnetic field. By using the reductive perturbation technique, a gyration-modified Korteweg-de Vries equation is derived for finite amplitude non-linear IAWs. Time-dependent numerical simulation shows the formation of an oscillating tail in front of the ion acoustic solitons in the presence of a weak magnetic field. It is also seen that the amplitude and width of solitons and oscillating tails are affected by the relevant plasma parameters such as quantum diffraction, positron concentration, and magnetic field. We have performed our analysis by extending it to account for approximate soliton solution by asymptotic perturbation technique and non-linear analysis via a dynamical system approach. The analytical results show the distortion of the shape of the localized soliton with time, and the non-linear analysis confirms the generation of oscillating tails.     

Thermally excited modes in a pure electron plasma

Thermally excited plasma modes are observed in near-thermal-equilibrium pure electron plasmas over a temperature range of 0.05相似文献   

Parametric excitation by a pump magnetic field in a high temperature plasma

The parametric growth rates of Alfvén waves, fast compressional waves and ion acoustic waves excited by a time modulated magnetic field are calculated for the case of a high temperature plasma with anisotropic pressure. The plasma is described by the C.G.L. model.     

Diagnostics for radial electric field measurements in hot magnetized plasmas

Measurements of the radial electric field profile in magnetically confined plasmas have yielded important new insights in the physics of L-H transitions, edge biasing and/or the active control of Internal and Edge Transport Barriers. The radial electric field is not an easy plasma parameter to diagnose. Techniques to measure the radial electric field in the plasma core are the Heavy Ion Beam Probe and the Motional Stark Effect. An indirect method that is quite often applied is to derive the electric field from measurements of the poloidal and toroidal rotation velocities via the radial ion force balance. This paper will first briefly explain the need for detailed measurements of the radial electric field profile. Subsequently, the various diagnostics to measure this parameter will be reviewed. The emphasis will be especially put on recent trends, rather than on an exhaustive overview. Presented at 5th Workshop “Role of Electric Fields in Plasma Confinement and Exhaust”, Montreux, Switzerland, June 23–24, 2002. Partner in the Trilateral Euregio Cluster