Neutron Yields Based on Transport Calculation in EAST ICRF Minority Heating Plasmas

Neutron diagnostics, including flux and energy spectrum measurements, have been applied on the experimental advanced superconducting tokamak (EAST). The absolute calibration of neutron yields has been achieved by a calculation method using the Monte Carlo automatic modeling (MCAM) system and the Monte Carlo N-Particles (MCNP) code. Since the neutron yield is closely related with the ion density and temperature, it is a good measure of plasma performance, especially the wave heating effect. In ion cyclotron range of frequencies (ICRF) experiments, the increase in the ion temperature derived by the neutron yield indicates an effective plasma heating. Minority protons damp a large fraction of the total wave power, and then transfer part of the energy to deuterium by collisions. Neutron spectrum measurements also indicate that no tail is created by high energy deuterons during ICRF heating. However, the ion temperature derived by the neutron yield is consistent with the result by using a poloidal X-ray imaging crystal spectrometer (PXCS), showing a reliable transport calculation.     

H_α/ D_α Measurements Based on Photo Diode Array in the HT-7 Tokamak

1. IntroductionThe measurement of H./D. emission, which canafford much information of the plasma, is one of the-,primary diagnostics in tokamak experiments. If theintensity Of H./D. emission along different chords ina poloidal plane are measured, with the ABEL inver-sion, one can get the H./D. emissivity, thus the spatial distribution of neutral H/D and its penetrationor ionization length. With the absolute brightness ofH./D. emission and assuming some symmetries inspatial distribution, …     

EAST运动斯塔克效应诊断的信号处理分析系统设计

运动斯塔克效应诊断利用光弹调制偏振测量技术可将偏振角的空间方向的测量转化为对二倍频信号强度比值的求取。为精准、快速地获取二倍频信号幅值,设计了基于FPGA的运动斯塔克效应诊断数字频谱分析系统,系统采用高速ADC采集运动斯塔克效应信号后送入FPGA,以EP2AGX125型FPGA为核心进行快速傅里叶变换获得信号频谱,求取二倍频分量的幅值进而计算出偏振角。经仿真与实验测试,该系统的测量精度好于5%,工作周期小于10 ms,满足MSE诊断信号处理要求。     

Calculation of Neutral Particle Energy Spectra in Tokamak by Using the Monte Carlo Method

1.IntroductionAlthoughmosthotplasmasarealmostcompletelyionized,thereare,nevertheless,neutra1atomsthatarecontinuallybeingformedintheplasma.Theseneutralsarisefromtheatomsandmoleculesbeingreleasedfromthewallofvacuumvessel.Recombi-nationofelectronsandionsintheplasmacanalsoformneutrals,buttheyareoflessimportantexceptatveryhighplasmadensitiesandatthecenteroflargeplasma.Someneutralssufferfromthereso-nantchargeexchangewiththeprimaryionandbe-comethefastneutrals.Thehigh-energyatomcanescapefromtheplasma…     

Steady-State Plasmas in KT5D Magnetized Torus

Steady-state plasma generated by electron cyclotron resonance （ECR） wave in the KT5D magnetized torus was studied using a fast high-resolution camera and Langmuir probes. It was found that both the discharge patterns taken by the camera and the plasma parameters measured by the probes were very sensitive to the working gas pressure and the magnetic configuration of the torus both without and with vertical fields. There existed fast vertical motion of the plasma. Tentative discussion is presented about the observed phenomena such as the bright resonance layer at a high gas pressure and the wave absorption mechanism at a low pressure. Further explanations should be found.     

One-Dimensional Vertical Electron Cyclotron Emission Imaging Diagnostic for HT-7 Tokamak

At the first stage of the electron cyclotron emission imaging （ECEI） diagnostic project on HT-7, a 16-channel vertical-resolved ECEI diagnostic has been developed and installed on HT-7 tokamak to measure electron cyclotron emission with a temporal resolution of 0.5 usec. The system works at a fixed frequency of 97.5 GHz. The sample volumes of the system are aligned vertically with a vertical channel spacing of 11 mm, and can be shifted across the plasma cross-section by varying the toroidal magnetic field. The high spatial resolution of the system is achieved by utilizing a low-cost linear mixer/receiver array and an optical imaging system. The focus location may be shifted horizontally when translating one of the optical imaging elements. The details of the system design and laboratory testing of the ECEI optics are presented together with the preliminary experimental results.     

Vertical Instability in EAST： Comparison of Model Predictions with Experimental Results

Growth rates of the axisymmetric mode in elongated plasmas in the experimental advanced superconducting tokamak （EAST） are measured with zero feedback gains and then compared with numerically calculated growth rates for the reconstructed shapes. The comparison is made after loss of vertical position control. The open-loop growth rates were scanned with the number of vessel eigenmodes, which up to 20 is enough to make the growth rates settled. The agreement between the growth rates measured experimentally and the growth rates determined numerically is good. The results show that a linear RZIP model is essentially good enough for the vertical position feedback control.     

Methods of Power Balance Analysis and Estimation of Current Density Profile for LHCD and IBW Discharges in HT-7 Tokamak

In this paper a simple code has been developed to analyze power balance and qualitatively evaluate current profiles for discharges with lower hybrid current drive （LHCD） and ion Bernstein wave （IBW） heating in the HT-7 tokamak. Electron and ion thermal diffusivity, profiles of the bootstrap current density and total plasma current density can be estimated by this code using the experimental data. This code offers an easy and reasonable means to understand plasma transport in HT-7.     

Photon Temperatures of Hard X-Ray Emission of LHCD Plasmas in HT-7 Tokamak

A detailed study of photon temperatures （Tph） of hard X-ray emission in lower hybrid current drive （LHCD） plasmas is presented. The photon temperature increases with the increase in plasma current and decreases with the increase in plasma density. In lower hybrid power and phase scanning experiments; there is no appreciable change in the photon temperature. The numerical results based on ray-tracing calculation and Fokker-Planck solver gives reasonable explanation for the experimental observation. Both experimental and numerical results reveal that the photon temperature depends mainly on global effects of the fast electron population, synergy between the fast electron and the loop voltage and the Coulomb slowing down.     

Enhanced Plasma Performance by ICRF Boronization

Boronization with carborane(C2B10H12)by ICRF been applied routinely to the walls of HT-7 super-conducting tokamak for the reduction of impurity influx.especially carbon and oxygen.Significant suppression of metallic impurties and radiating power fraction are achieved.The imporved confinement for both particle and energy is observed in full range of operation parameters.Energy balance analysis shows that electron heat diffusion coefficient is strongly reduced.Measurements by Langmuir probes at the edge plasma show that poloidal velocity shear after boronization is changed to a profile to profile favoring to good confinement.The main emphasis of this paper is to describe effects of boronization on aspects of the enhanced plasma performance.