Optics System Design of Microwave Imaging Reflectometry for the EAST Tokamak

A front-end optics system has been developed for the EAST microwave imaging reflectometry for 2D density fluctuation measurement.Via the transmitter optics system,a combination of eight transmitter beams with independent frequencies is employed to illuminate wide poloidal regions on eight distinct cutoff layers.The receiver optics collect the reflected wavefront and project them onto the vertical detector array with 12 antennas.Utilizing optimized Field Curvature adjustment lenses in the receiver optics,the front-end optics system provides a flexible and perfect matching between the image plane and a specified cutoff layer in the plasma,which ensures the correct data interpretation of density fluctuation measurement.     

Investigation of phase modulation and propagation-route effect from unmatched large-scale structures for Doppler reflectometry measurement through 2D full-wave modeling

To interpret the common symmetric peaks caused by the large-scale structure in the complex S(f) spectrum from the heterodyne Doppler reflectometry(DR) measurement in EAST, a 2D circular-shaped O-mode full-wave model based on the finite-difference time-domain method is built. The scattering characteristics and the influences on the DR signal from various scales are investigated. When the structure is located around the cutoff layer, a moving radial or poloidal large-scale structure k_θ■...     

Experimental studies on the propagation of whistler-mode waves in a magnetized plasma structure with a non-uniform density

Propagation of whistler-mode waves in a magnetized plasma structure is investigated in the Keda linear magnetized plasma device. The magnetized plasma structure has its density peak in the center, and the background magnetic field is homogeneous along the axial direction. A whistlermode wave with a frequency of 0.3 times of electron cyclotron frequency( fce) is launched into the plasma structure. The wave normal angle(WNA) is about 25°, and the wavefront exhibits a wedge structure. During propag...     

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.     

A Non-neutral Plasma Device: Electron Beam Penning Trap

1.IntroductionPenningtrapshavebeenwidelyusedtotrapchargedparticles,suchaselectronsorions,forstudyonthefundamentalpropertiesofparticles,andthetransportandequilibriumpropertiesofnon--neutralplasmas[1-4].InaPenningtrap,auniformaxialmagneticfieldprovidesradialconfinement,whiletheelectricfieldbetweentheelectrodesprovidesaxialone.Thetrapcanconfineasmallnumberofchargedparticlesforverylongtime.However,becauseoftheself-electricfieldeffect,themaximumdensityofnonneutralplasma(electron)radicallyconfinedb…     

脉冲染料激光的线宽压缩与测量

设计并自制了一种平行平面腔法布里-珀罗干涉仪,将脉冲染料激光器的输出线宽由4 GHz压缩至340 MHz。采用法布里-珀罗标准具拍照法对激光线型进行实时监测,实现了脉冲激光线型的同步扫描;配合碘吸收谱测量,搭建了经线宽压缩的脉冲染料激光的100 MHz量级的精细波长调谐及标定系统。将该激光系统用于氧化物阴极放电氩等离子体的激光诱导荧光诊断中,验证了线宽压缩系统的可行性,离子速度分布函数的速度分辨率可达200 m/s。     

利用双等离子体装置产生非均匀等离子体

在双等离子体实验装置中,采用单边放电的方式在源区产生等离子体,通过扩散和电子碰撞电离可以在实验区产生密度分布不均匀的等离子体.利用静电探针测量了实验区等离子体的状态参数及其空间分布,结果显示:该装置可以提供一个径向相当宽范围内密度基本均匀,轴向密度分布指数衰减的等离子体环境,其不均匀性标长与放电气压成反比.该装置可以提供不均匀性可控的非均匀等离子体源.     

Upgrading of the Magnetic Confinement Plasma Device KT-5E

In this article we present ideas of providing appropriate poloidal magnetic field for helimaks to help to generate toroidal magnetic plasma torus.Placing a conductive ring in the center of the cross-section to induce a suitable current,we change the helical magnetic field lines in the helimak discharge into magnetic surface.In this kind of discharge,the plasma density is greatly increased,and the corresponding density fluctuation is significantly decreased,showing a better confinement by magnetic shear.It allows more flexible and efficient experimental investigations on the toroidal magnetic confinement plasmas to be carried on in this kind of device.     

Spontaneous current relaxation in NBI heated plasmas on EAST

We report on current profile evolution in EAST NBI driven plasmas where two neutral beams are injected,one during the current ramp phase and the second during flattop.At the end of the current ramp phase,it is found that a flat q profile with q0?~?1 is achieved with low magnetic shear in the core.It is observed that plasma current and density both relax much faster than resistive time,even in the absence of sawtooth activity when H–L transition occurs.Density fluctuations associated with magnetic perturbations(3/2) as a precursor to the H–L transition are observed.It is likely that these modes play a role in fast current transport.     

Design of Thomson scattering diagnostic system on linear magnetized plasma device

In addition to the magnetic confinement fusion plasma, Thomson scattering has been applied to measure electron density and temperature of low-temperature plasmas. Based on a linear magnetized plasma device, a set of Thomson scattering diagnostic system is designed to diagnose the plasma with ${n}_{{\rm{e}}}={10}^{18}{\unicode{x02013}}{10}^{19}\,{{\rm{m}}}^{-3}$ and ${T}_{{\rm{e}}}=2{\unicode{x02013}}5$ eV. Due to low plasma temperature and density, this diagnostic system needs high spectral resolution and collection efficiency to meet the requirements of electron velocity distribution function measurements. Through the bench test, it is confirmed that the spectral resolution reaches 0.01 nm, and theoretical collection efficiency is high enough to obtain a Thomson scattering spectrum by 1000 accumulations.