Measurement of molybdenum ion density for L-mode and H-mode plasma discharges in the EAST tokamak

We report the measurement of total molybdenum ion density for L-mode and H-mode plasmas on EAST using spectral lines observation and calculation based on an impurity transport code. A flat-filed extreme ultraviolet spectrometer with some spatial resolution is used to obtain the radial profiles of molybdenum spectral line emissions. The absolute calibration for the extreme ultraviolet spectrometer is finished by comparing the calculated bremsstrahlung intensity with the readings of CCD detector. Molybdenum ion transport study is performed using the radial ion density profiles and one-dimensional impurity transport code STRAHL. The total molybdenum density profiles are determined from the transport analysis. The molybdenum density during L-mode and H-mode phases are obtained, which are about 3 and 4 orders of magnitude smaller than the electron density, respectively. An inward pinch is found during the H-mode phase that leads to the peaked profile of molybdenum density.     

The carbon impurity ohmic discharges on particle transport in the HT-7 tokamak

The line-integrated optical measurement of impurity radiation profiles for the study of light impurity transport is performed in the HT-7 tokamak. The carbon impurity line emissivity is obtained by Abel inversion. The radial transport behaviours of carbon impurities at different central line averaged electron densities ne are investigated in ohmic discharges. The diffusion coefficient Dk（r）, the convection velocity Wk（r） and the total flux of the impurity ions Fk decrease with the increase of ne, which shows a reduction in the impurity particle transport at higher electron densities.     

HT—6M托卡马克欧姆加热下氧杂质的输运模拟

本文利用HT-6M托卡马克上现有的实验数据,对氧杂质进行了输运模拟,给出了HT-6M托卡马克在欧姆加热下氧杂质的输运特性,空间分布和辐射能量。     

HL-lM装置杂质粒子输运与约束特性

在HL-lM装置上利用激光吹气技术,在等离子体边缘瞬态注入少量Al杂质粒子,通过对真空紫外光谱和软X射线区的杂质辐射测量,分别研究了欧姆等离子体和低杂波电流驱动等离子体两种情况下,Al杂质粒子输运与约束特性。结果表明：在欧姆等离子体和低杂波电流驱动等离子体两种情况下,等离子体中心区,在没有MHD锯齿震荡和有MHD锯齿震荡非锯齿破裂期间,杂质粒子输运基本上受新经典规律支配;在有MHD锯齿震荡锯齿破裂期间,杂质粒子输运受MHD不稳定性支配,但其时间很短(通常小于300μs),所以在这种情况下,杂质粒子输运的平均效应比新经典值稍大。而约束区杂质粒子输运则比新经典的值大很多,是反常的。在一定条件下低混杂波电流驱动可以改善等离子体粒子约束。     

Dynamic regime of conduction in a 1D system with a single impurity

A new regime of electron transport through an impurity in 1D conductors, which resembles the Josephson effect in its manifestations, is predicted. Passage of current through the impurity under voltages above the threshold value is accompanied with generation of ac current oscillations. The temperature below which the effect can be observed, the threshold voltage, and the frequency range are determined by the impurity potential and the strength of electron-electron interaction. The generation line width and the current-voltage characteristics are determined.     

Preliminary analysis of impurity transport in HL-2A ohmic discharges

This paper describes the behaviour of impurity transport in HL-2A ohmic discharges. In 2005, small quantities of metallic impurities （A1, Ni and Ti） were successfully injected into HL-2A plasmas by laser blow-off technique, and their progression was followed by the soft x-ray cameras with good spatial and temporal resolutions. The impurity confinement time is estimated from the characteristic decay time of the soft x-ray signal of the injected impurities, and it is about 30-60 ms. The transport coefficients of impurities （including diffusion coefficient and convection velocity） in radial different region have been derived by using a one-dimenslonal impurity transport code, the results present that diffusion coefficient is much smaller in the central region of plasmas than the outside of it, and it is much larger than that of neoclassical theory predictions; namely, it is anomalous.[第一段]     

背散射方法研究金属中注入轻离子分布

用能量为MeV量级的α粒子背散射方法测定了大剂量N⁺ (5×10¹⁷ atom/cm²,100keV)注入铁膜(厚约4000?)及铁块(工业纯)的注入离子的浓度-深度分布。由于大剂量杂质的注入,使基体背散射谱出现“凹坑”,提出了一种利用“凹坑”计算杂质分布的方法。 关键词：     

Nitrogen diffusion parameters in ion-implanted tungsten single crystals

Diffusion of nitrogen implanted in single-crystal tungsten was studied in the temperature range 700–820° C. Measurements were carried out using a method of nondestructive determination of diffusivities (developed by the authors) from the dynamics of variation in the surface impurity concentration. The initial distribution and diffusion profiles for various annealing times were determined by secondary ion mass spectrometry. The relative surface concentration of nitrogen was measured by Auger electron spectroscopy. Several fluxes of impurity atoms in the surface region of ion-doped tungsten were experimentally detected to exist. Under the assumption that the fluxes interact with each other, the temperature dependences of the nitrogen diffusivities in the flux associated with dislocations generated by ion implantation and in the flux associated with the bulk diffusion mechanism were determined. Nitrogen diffusion is characterized by a rather low activation energy, namely, 0.15 and 0.75 eV for dislocation and bulk mechanisms, respectively.     

Investigation of impurity transport using laser blow-off technique in the HL-2A Ohmic and ECRH plasmas

Impurity transports in two neighboring discharges with and without electron cyclotron resonance heating(ECRH)are studied in the HL-2A tokamak by laser blow-off(LBO) technique.The progression of aluminium ions as the trace impurity is monitored by soft x-ray(SXR) and bolometer detector arrays with good temporal and spatial resolutions.Obvious difference in the time trace of the signal between the Ohmic and ECRH L-mode discharges is observed.Based on the numerical simulation with one-dimensional(1D) impurity transport code STRAHL,the radial profiles of impurity diffusion coefficient D and convective velocity V are obtained for each shot.The result shows that the diffusion coefficient D significantly increases throughout the plasma minor radius for the ECRH case with respect to the Ohmic case,and that the convection velocity V changes from negative(inward) for the Ohmic case to partially positive(outward) for the ECRH case.The result on HL-2A confirms the pump out effect of ECRH on impurity profile as reported on various other devices.     

用真空紫外光谱研究HL—1装置上氧杂质浓度和输运

本文叙述用真空紫外光谱确定HL-1装置杂质浓度的方法,详细描述了用于解释光谱测量的杂质输运模型S1TCODE。为了在每次放电结束后就容易、迅速地获得这些结果,引入了一种快速分析方法。对HL-1装置在通常放电,器壁碳化和抽气孔栏等不同特性放电情况下氧杂质浓度和输运特性进行了初步分析。