Investigation of Some MHD Events in the SUNIST Spherical Tokamak

Internal reconnection event （IRE）, which is characterized by a perturbation in plasma current Ip, loop voltage Vloop, Hα radiation and magnetic perturbation dBp...     

Simulation Study for Divertor Geometry and Gas Puffing to Handle Huge Exhaust Power in HL-2M with SOLPS5.0

One of the critical issues to be solved for HL-2M is the power exhaust.Divertor target plate geometry strongly influences the plasma profiles by controlling the neutral recycling pattern,which in turn has a strong effect on the symmetry and stability of the divertor plasma and finally on the whole edge region.The numerical simulation SOLPS5.0 package is used to design and explore the divertor target plates for HL-2M.We start with the choice of a proper target plate geometry,which has a smaller incidence angle in the permissible space,and then discuss the method of gas puffing to reduce the heat flux density on the target and the effects of gas puffing on the divertor plasma performance.     

Analysis and design of the Alfven wave antenna system for the SUNIST spherical tokamak

Analysis and design of the Alfven wave antenna system for the SUNIST spherical tokamak are presented. Two candidate antenna concepts, folded and unfolded, are analyzed and compared with each other. In the frequency range of Alfven resonance the impedance spectrums of both two concept antennas for major modes are numerically calculated in a 1-D MHD framework. The folded concept is chosen for engineering design. The antenna system is designed to be simple and requires least modification to the vacuum vessel. The definition of the antenna shape is guided by the analyses with constraints of existing hardware layouts. Each antenna unit consists of two stainless steel straps with a thickness of 1 mm. A number of boron nitride tiles are assembled together as the side limiters for plasma shielding. Estimation shows that the structure is robust enough to withstand the electromagnetic force and the heat load for typical discharge duty cycles.     

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.     

Analysis of the Plasma Properties Affected by Magnetic Confinement with Special Emphasis on Helicon Discharges

A one-dimensional radial non-uniform fluid model is employed to study plasma behaviors with special emphasis laid on helicon discharges. The plasma density ne, electron temperature Te, electron azimuthal and radial drift velocities are investigated in terms of the plasma radius rp, magnetic field intensity B0 and gas pressure p0, by assuming radial ambipolar diffusion and negligible ion cyclotron movement. The results show that the magnetic confinement plays an important role in the discharge equilibrium, especially at low pressure, which significantly reduces Te compared with the case of a negligible magnetic field effect, and higher B0 leads to a greater average plasma density. Te shows little variations in the plasma density range of 1011 cm-3- 1013 cm-3 for p0 〈 3.0 mTorr. Comparison of the simulation results with experiments suggests that the model can make reasonable predictions of Te in low pressure helicon discharges.     

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.     

Analysis of Divertor Heat Flux with Infrared Thermography During Gas Fuelling in the HL-2A Tokamak

In HL-2A tokamaks, the behavior of heat flux deposited on the divertor targets has been studied during deuterium gas fuelling. The heat flux is reduced significantly after supersonic molecular beam injection （SMBI） fuelling during Ohmic and electron cyclotron resonance heating （ECRH） divertor discharges. The SMBI fuelling causes an increase in the plasma density and this change results in the experienced change of the edge properties. Most of this reduction in divertor target heat flux occurs together with a high plasma radiation region located at near the X-point. The largest reduction in heat flux profiles is observed at the outboard divertor separatrix strike point, while the heat flux far from the strike point remains almost unchanged. In particular, with SMBI multi-pulses gas fuelling, a partially detached divertor regime is observed with a highly radiating region at the X-point. With the onset of the partially detached divertor regime, a sudden drop in both heat flux and power flow on the divertor target is observed. The reduction in power load on the divertor targets is roughly equal to the increase in plasma radiation loss.     

HT-7装置上充气对低杂波耦合影响的实验及分析

在低杂波（LHW）天线端口充D₂和CD₄,发现LHW的耦合效果能得到明显改善,充气后LHW的反射系数基本降为6%左右。不同窗口充气对波的耦合和等离子体密度的影响不同,其原因是改善耦合的关键是提高刮削层（SOL）内等离子体的密度。D₂与CH₄对LHW耦合影响的实验结果表明：D₂对LHW的耦合效果影响略好于CH₄,但D₂对等离子体密度的影响明显高于CH₄,原因是D₂对电子密度的贡献更大。     

Primary Results of Lithium Coating for the Improvement of Plasma Performance in EAST

First lithium coating associated with ion cyclotron range of frequency (ICRF) plasma was performed successfully in EAST. Results in reduction of both residual impurity and deuterium in the vacuum vessel were obtained. Particularly the partial pressure of deuterium after the lithium coating was reduced by about a factor of 5. Impurity radiation in the plasma was reduced and electron temperature increased by about 50%. Moreover, reproducible plasma discharges with high parameters, such as higher plasma current and density, could be easily obtained. These results showed that plasma performance was improved. Even though only 2 g of lithium were injected, the effective lifetime of the Li film was raised up to 40 shots.     

Development of In-Situ Gas Analyzer for Hydrogen Isotopes in Fusion Fuel Gas Processing

To develop a real time and in-situ process gas analyzer for fusion fuel gas processing systems, application study of laser Raman spectroscopy was performed by measurement of hydrogen isotopes. Using an Ari on type laser of which wavelength 488 nm, power 0.7 W, and single pass irradiation method, Raman spectra of hydrogen isotopes were measured and intensities of the Stokes rotational lines and Q-branch were quantitatively analyzed. The Stokes rotational lines at 587, 443 and 415 cm¹ were selected as suitable ones for quantitative analysis of H₂, HD and D₂. Normalizing the Raman intensity of partial pressure H₂ as 100, relative Raman intensity ratio of H₂:HD:D₂ was obtained as 100:58:47. The detection limit for hydrogen was estimated as 0.05 kPa in partial pressure and 500 ppm in concentration. But multiple pass method further improved the detection limit to 100 ppm.     

氦气试验回路中的氦净化

为了减少结构材料的腐蚀并验证高温气冷实验堆中的氦净化工艺，在氦气试验回路中设置了氦净化系统并进行了试验。试验结果表明，净化流量为５０ｍ＾３／ｈ的主要由分子筛和深活性炭床组成的氦净化系统，能把氦中２００００ｃｍ＾３／ｍ＾３的化学杂质净化到７６ｃｍ＾３／ｍ＾３以下。所采用的氦中痕量杂质分析测量技术达到１０＾－１ｃｍ＾３／ｍ＾３精度。     

Preliminary Study of Isotopic Methanes Analysis by Laser Raman Spectroscopy for In-Situ Measurement at Fusion Fuel Gas Processing

Application of laser Raman spectroscopy for fusion fuel gas processing was studied by measuring isotopic methanes exchanged with hydrogen isotopes, which are considered to be a major impurities in the processing. For experimental gases, isotopically equilibrated deuterium and methane were prepared in the presence of solid catalyst. Large Raman scattering peaks of v ₁, bands were observed at 2,917 cm^?1 for CH₄ and at 2,100-2,200 cm_?1 for deuterated derivatives of methane C(H,D)₄. Under a spectral resolution of 5 cm_?1, the v ¹ bands of CH₃D and CH₂D₂ were observed as an overlapped peak, the relative absolute Raman intensity ratio of each isotopic methane was obtained as CH₄: CH₃D+CH₂D₂: CHD₃: CD₄=230: 74: 144: 100. On the other hand, the Raman intensity ratio obtained from pure deuterated standard methane was CH₄: CH₃D: CH₂D₂: CHD₃: CD₄=230: 53: 33: 115: 105. It was confirmed that isotopically equilibrated hydrogen isotopes and methane mixed gas would be applicable for an alternative standard gas for fusion fuel processing gas analyzing system.     

核电厂卧式蒸汽发生器热工性能的计算和分析

文章基于卧式蒸汽发生器的工作原理及内部结构特点,建立了卧式蒸汽发生器数学物理模型,开发了针对卧式蒸汽发生器的热工水力程序。基于在役核电站卧式蒸汽发生器的设计参数,对程序进行了校核。该程序可以用来研究卧式蒸汽发生器内主要热工参数的分布情况,为卧式蒸汽发生器设计、安全分析提供指导;也可以根据在役核电站的历史运行数据对蒸汽发生器现阶段热性能进行分析评定,对蒸汽发生器一段时间内的热性能进行预测,为蒸汽发生器的运行、检修以及更换提供依据。     

Analysis of an Ar plasma jet in a dielectric barrier discharge conjugated with a microsecond pulse

In this work, an Ar plasma jet generated by an AC-microsecond-pulse-driven dielectric barrier discharge reactor, which had two ring-shaped electrodes isolated from the ambient atmosphere by transformer oil, was investigated. By special design of the oil insulation, a chemically active Ar plasma jet along with a safe and stable plasma process as well as low emission of CO and NO_x were successfully achieved. The results indicated that applied voltage and frequency were basic factors influencing the jet temperature, discharge power, and jet length, which increased significantly with the two operating parameters. Meanwhile, gas velocity affected the jet temperature in a reverse direction. In comparison with a He plasma jet, the Ar plasma jet had relatively low jet temperature under the same level of the input parameters, being preferable for bio-applications. The Ar plasma jet has been tested to interact with human skin within 5 min without the perception of burnt skin and electrical shock.     

高温气冷堆热气导管的结构稳定性分析

热气导管是高温气冷堆中氦气循环的重要流道,其在各工况下的结构完整性与稳定性关系到反应堆是否能运行安全。本文详细分析了热气导管在事故工况下所承受的压力载荷,包括绝热纤维对管壁的压力以及一回路失压事故时发生氦气泄漏产生压力;并根据得到的压力载荷计算了热气导管承受外压时的结构稳定性。计算结果表明热气导管在事故工况的压力载荷作用下能够保持结构的完整性并且不会发生失稳。     

85Kr测厚源的输出性能研究

为指导⁸⁵Kr测厚源的制备,采用两种材质、两种活性区、两种丰度的85Kr原料气制备一批同等活度（7.4 GBq）的测厚源,采用自行研制的⁸⁵Kr源β输出电压装置对制备的测厚源输出电压进行测量。结果表明,采用钛材质、小活性区、20%丰度原料的测厚源输出电压更高。钛材质的源窗、小活性区的源壳、高丰度的原料对β射线的吸收更少,因此在制备某种活度的⁸⁵Kr测厚源时,为提高射线输出,应优先采用钛材质、小活性区、高丰度的原料。     

Performance of Dielectric Barrier Discharge Reactors on Elemental Mercury Oxidation in the Coal-Fired Flue Gas

The oxidation of elemental mercury （Hg~） by dielectric barrier discharge reactors was studied at room temperature, where concentric cylinder discharge reactor （CCDR） and surface discharge plasma reactor （SDPR） were employed. The parameters （e.g. Hg^0 oxidation efficiency, energy constant, energy yield, energy consumption, and O3 concentration） were discussed. From comparison of the two reactors, higher Hg^0 oxidation efficiency and energy constant in the SDPR system were obtained by using lower specific energy density. At the same applied voltage, energy yield in the SDPR system was larger than that in the CCDR system, and energy consumption in the SDPR system was much less. Additionally, more 03 was generated in the SDPR system. The experimental results showed that 98% of Hg^0 oxidation efficiency, 0.6 J·L^-1 of energy constant, 13.7 μg·J^-1 of energy yield, 15.1 eV·molecule^-1 of energy consumption, and 12.7 μg·J^-1 of O3 concentration were achieved in the SDPR system. The study reveals an alternative and economical technology for Hg^0 oxidation in the coal-fired flue gas.     

Method for Improving the Collecting Performance of Iodine Samplers under High Relative Humidity

In airborne radioiodine monitoring, it is essential to establish an effective sampling technique that gives results independent of the form taken by the radioiodine and that works effectively under high humidity. Experiments were made to improve the performance of an iodine sampler embodying (a) cellulose asbestos filter paper (Toyo Roshi, Type HE-40) and activated charcoal filter paper (Toyo Roshi, Type CP-20) and (b) HE-40 filter paper and activated charcoal cartridge (Toyo Roshi, Type CHC-50). Based on the results, a new sampler was devised in which the air is heated to 70°～90°C before reaching the filters. The dependence of the collecting efficiency on the chemical form taken by the airborne iodine and also on the duration of sampling period was studied.

Severe conditions of environment, such as high humidity, were simulated in the experimental apparatus. The airborne radioiodine used was a mixture of inorganic and organic iodides, identified by radio-gaschromatography. It was found that the collecting efficiency of the sampler with activated charcoal cartridge and the activated charcoal filter paper, respectively, exceeded 99.5% and 85%, regardless of the form of airborne iodine even at 100% relative humidity throughout the whole range of sampling duration up to 16 hr. Under conditions of high humidity, the collecting efficiencies were found superior to that of charcoal filter paper and charcoal cartridge impregnated with TEDA or SnI₂ used without air heating.     

Design and Fabrication of a Movable Langmuir Probe for Plasma Edge Parameters Measurement in the IR-T1 Tokamak

For the edge plasma parameters measurement, a movable Langmuir probe is fabricated and installed on the IR-T1 tokamak. The set-up consists of two sets of single Langmuir probes with tungsten tip movable in the radial direction. Edge plasma parameters including electron temperature, Ion density, floating potential and the corresponding radial changes are measured. Using two-point correlation technique clearly reveal that in the SOL region the poloidal propagation of floating potential fluctuation is in the direction of ion diamagnetic drift and in the edge it propagates in the electron diamagnetic drift direction.