Set－up of a Pure Electron Plasma Device

An electron Penning-Malmberg trap,which can confine an electron column and provide a good platform to investigate the cross-filed transportation of strongly magnetized electron plasma ,has been set up.With the device,an electron plasma with a density of 10^7 cm^-3 can be confined for a relatively long time.The structure of the trap,electron source,as well as the way how th measure electron plasma density profile and velocity distrbustion are introduced in detail.     

Electron Heating of LHCD Plasma in HT-7 Tokamak

Electron heating via lower hybrid current drive （LHCD） has been investigated in HT-7 superconducting tokamak. Experiments show that the central electron temperature Te0, the volume averaged electron temperature 〈 Te 〉 and the peaking factor of the electron temperature QTe = Teo/〈 Te 〉 increase with the lower hybrid wave （LHW） power. Simultaneously the electron heating efficiency and the electron temperature as the function of the central line-averaged electron density （ne） and the plasma current （Ip） have also been investigated. The experimental results are in a good agreement with those of the classical collision theory and the LHW power deposition theory.     

Electron Plasma Relaxation Processes

The solution of the Vlasov equation for the longitudinal electron plasma wave is obtained by using Neumann series method. The electron relaxation process is analytically described by the superposition of expressions for electron streamings and Coulomb collisions.

The currently established formula for the longitudinal plasma wave is also explained by the closed-form solution of the Vlasov equation.

The expression effectively describes the detailed physical processes of the electron plasma wave relaxation both in space and time.     

Behaviors of Electron Heat Transportation in HT-7 Sawtoothing Plasma

It is found that in HT-7 ohmic plasma, main energy loss comes from electron heat conduction, hence quantitative data of electron heat diffusivity is a very important issue for investigation of electron heat transportation behavior in different target plasmas so as to get high performance plasma. A time-to-peak method of the heat pulse propagation originating from the sawtooth activity on the soft x-ray intensity signal has been adopted to experimentally determine electron heat diffusivity χe^HP on the HT-7 tokamak. Aiming to improve the signal-to-noise (S/N) ratio of the original signal to get a stable and reasonable electron heat diffusivity χe^HD value, some data processing methods, including average of tens of sawteeth, is discussed. The electron heat diffusivity χe^HP is larger than χe^PB which is determined from the balance of background plasma power. Based on variation of the measured electron heat diffusivity χe^HP , performances of different high confinement plasmas are analyzed.     

Spaced-Resolved Electron Density of Aluminum Plasma Produced by Frequency-Tripled Laser

1 Introduction X-ray spectra emitted from hot dense plasmas pro- vide an important diagnostic tool to infer local plasma parameters, particularly the ionization stage, density, and temperature [1]. Analysis of the emission spectra of highly stripped ions from laser-produced plasmas is potentially the most direct and reliable method for de- ducing the ultra-high-pressure plasma conditions. The development of the diagnostic methods for electron den- sity will produce important effect on the stud…     

Standing Ultrashort Relativistic Solitons in Overdense Plasmas

By using a one-dimensional self-consistent relativistic fluid model, an investigation is made numerically on relativistic electromagnetic solitons with a high intensity in cold overdense plasmas with an electrons＇ initial velocity opposite to the laser propagating direction. Two types of standing solitons with zero group velocity are found at the given electrons＇ initial velocities. One is single-humped with a weakly relativistic intensity; the another is multi-humped with a strong relativistic amplitude. The properties of these two types of solitons are presented in detail.     

The Electron Temperature Estimation Using Soft X-Ray Imaging in HT-7 Tokamak

In order to estimate the electron temperature soft x-ray imaging diagnostics using a double filter technique has been developed in the HT-7 tokamak. The chosen thicknesses of the Be foil are 12.5 μm and 70 μm, respectively. In this article both the main design of the diagnostic configuration and the method to estimate the electron temperature are presented. The results agree with those estimated from the soft x-ray pulse height analyzer （PHA）. The main causes of systematic error have also been investigated.     

A Magnetic Electron Analyzer for Plasma Focus Electron Energy Distribution Studies

The paper describes the construction of a magnetic electron analyzer for pulsed beam electron energy distribution studies. The single shot information is obtained using a NMOS linear image sensor. Both the energetical and the sensitivity calibration were performed using careful numerical simulations. For simplicity, the signals can be read on an oscilloscope, and they are transmitted via an optic fiber, which allows the analyzer to work while connected to high voltage. The analyzer was successfully implemented on a 15 kV/3 kJ plasma focus device and was used to study the electron energy distribution in the 30–660 keV range..     

Direct Measurements of the Electron Energy Flux versus Electron Temperature Gradient in Tokamak Discharges

Electron thermal transport is one of the most complex processes in fusion plasmas.It is generally described by a simple thermal diffusivity in transport analyses of discharges,but there is evidence of critical gradient effects with moderate stiffness.By analyzing periodic perturbations to an equilibrium,one can measure the variations in electron energy flux and electron temperature gradient over the perturbation cycle,obtaining the flux as a function of gradient over the range of parameters generated by the perturbation.Although time-dependent transport analysis is very sensitive to noise in the input data,averaging over many cycles of a periodic perturbation can provide data of sufficient quality.The analyses presented here are based on the ECE temperature data with high spatial and temporal resolution and full profile coverage on DIII-D for sawteeth and modulated ECH heating.     

伴随内转换电子发射的俄歇电子能量及强度计算

简要介绍了伴随内转换电子发射产生的俄歇电子能量与强度的计算方法、计算程序及工作流程，并以^129Iβ^-衰变为例说明其具体应用。     

Electromagnetic Particle-in-Cell Simulations of Electron Holes Formed During the Electron Two-Stream Instability

Previous electrostatic particle-in-cell (PIC) simulations have pointed out that electron phase-space holes (electron holes) can be formed during the nonlinear evolution of the electron two-stream instability. The parallel cuts of the parallel and perpendicular electric field have bipolar and unipolar structures in these electron holes, respectively. In this study, two-dimensional (2D) electromagnetic PIC simulations are performed in the x y plane to investigate the evolution of the electron two-stream instability, with the emphasis on the magnetic structures associated with these electron holes in different plasma conditions. In the simulations, the background magnetic field (Bo= Boex ) is along the x direction. In weakly magnetized plasma (Ωe < ωpe , whereΩe and ωpe are the electron gyrofrequency and electron plasma frequency, respectively), several 2D electron holes are formed. In these 2D electron holes, the parallel cut of the fluctuating magnetic field δBx and δBz has unipolar structures, while the fluctuating magnetic field δB y has bipolar structures. In strongly magnetized plasma (Ωe > ωpe ), several quasi-1D electron holes are formed. The electrostatic whistler waves with streaked structures of E y are excited. The fluctuating magnetic field δB x and δBz also have streaked structures. The fluctuating magnetic field δBx and δB y are produced by the current in the z direction due to the electric field drift of the trapped electrons, while the fluctuating magnetic field δBz can be explained by the Lorentz transformation of a moving quasielectrostatic structure. The influences of the initial temperature anisotropy on the magnetic structures of the electron holes are also analyzed. The electromagnetic whistler waves are found to be excited in weakly magnetized plasma. However, they do not have any significant effects on the electrostatic structures of the electron holes.     

Effects of Finite Aspect Ratio and Noncircular Plasma Flux Surface on Electron Temperature Gradient Driven Modesd

A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.     

电子磁谱仪法测量超热电子温度

利用超热电子磁谱仪测量了紫外超短脉冲激光与固体等离子体相互作用产生超热电子的能谱,在无预脉冲、激光强度为1017 W/cm2 条件下,紫外超短脉冲激光与固体(Cu)等离子体相互作用产生超热电子的能谱呈双温麦克斯韦分布,超热电子温度为81 keV,激光吸收的主导机制为真空吸收。     

Dust Streaming Effect on Dust Acoustic Solitary Wave in Magnetized Dust-Ion Plasmas

The dust acoustic solitary structures in the presence of dust streaming are obtained through Sagdeev's pseudopotential approach in magnetized dustion plasmas. It is found that dust streaming plays a destructive role in the formation of dust acoustic solitary structures. However, the wave amplitude increases with the increase in the Mach number and obliqueness of the wave in the presence of contant dust streaming along a uniform external magnetic field. The numerical results are applied to Saturn's F-rings for illustrative purposes.     

Effects of the Hot Electron Interchange Instability on Plasma Confined in a Dipolar Magnetic Field

The Levitated Dipole Experiment (LDX) explores confinement and stability of plasma created within the dipole field of a strong superconducting magnet. During initial experiments, long-pulse, quasi-steady state discharges that last more than 10 s and have peak beta of more than 20% are studied. The plasma is created by multi-frequency electron cyclotron resonance heating (ECRH) at 2.45 and 6.4 GHz. A population of energetic electrons, with mean energies above 50 keV, dominates the plasma pressure. Creation of high pressure, high beta plasma is possible only when intense hot electron interchange (HEI) instabilities are stabilized by sufficient neutral gas fueling. The instabilities resonate with the magnetic drift motion of the energetic electrons and can cause rapid radial transport. Measurements of the electrostatic and magnetic fluctuations of the HEI instability are described along with observations of the instability’s spectral characteristics. Fluctuations of the outer poloidal field induced by the HEI show a rapid evolution of the perturbed pressure profile.      

赝火花脉冲电子束束流传输特性分析

对赝火花放电实验中观察到的脉冲电子束的椭圆形束斑、自箍缩以及细丝效应进行了介绍，并用电磁动力学分析了其成因和影响因素。     

A 20 kV, 5 A, 1 ns Risetime Pulsed Electron Beam Source

A 20 kV, 1 ns risetime pulsed electron beam source was developed using an extremely small gap （0.1 mm） diode driven by a sub-nanosecond risetime, 10 kV rectangular pulse generator. A beam current of 5 A was detected by using a fast response Faraday cup at a distance of 2 cm away from a grid anode. The shot to shot variation of the electron beam pulse was less than 10%.     

10 MeV辐照电子直线加速器控制系统

本工作为1台10 MeV辐照用电子直线加速器研制控制系统。该控制系统采用分布式网络控制,由多个子系统构成。硬件采用SIEMENS PLC芯片和监控计算机,PLC间采用PROFIBUS、MPI等高速总线进行连接,与监控计算机采用以太网连接,使用TCP/IP协议,能在互联网上远程监视和维护,进行网络控制。软件采用STEP 7和C语言等编写,对各子系统及子系统间连接均采用独立的数据块和功能函数块。部分硬件功能由软件来实现,使得整个系统更易于测试、制造和维护升级。     

Electron Cyclotron Heating (ECH) of Tokamak Plasmas

Electron cyclotron heating (ECH) is one of the intense methods of plasma heating, and which utilizes the collisionless electron-cyclotron-resonance-interaction between the launched electromagnetic waves (called electron cyclotron waves) and electrons which are one of the constituents of the high temperature plasmas. Another constituent, namely the ions which are subject to nuclear fusion, are heated indirectly but strongly and instantly (in about 0.1 s) by the collisions with the ECH-heated electrons in the fusion plasmas. The recent progress on the development of high-power and high-frequency millimeter-wave-source enabled the ECH experiments in the middle size tokamaks such as JFT-2M (Japan), Doublet III (USA), T-10 (USSR) etc., and ECH has been demonstrated to be the sure and intense plasma heating method. The ECH attracts much attention for its remarkable capabilities; to produce plasmas (pre-ionization), to heat plasmas, to drive plasma current for the plasma confinement, and recently especially by the localization and the spatial controllability of its heating zone, which is beneficial for the fine controls of the profiles of plasma parameters (temperature, current density etc.), for the control of the magnetohydrodynamic instabilities, or for the optimization/improvement of the plasma confinement characteristics. Here, the present status of the ECH studies on tokamak plasmas are reviewed.