Investigation of LHCD Efficiency and Transformer Recharging in the EAST Tokamak

The efficiency of lower hybrid current drive(LHCD) for limiter and divertor configurations in the EAST tokamak is investigated using hot electrical conductivity theory and experimental formulas.The results indicate that the efficiency of current drive in divertor geometry is slightly higher than that in limiter one.To interpret the experimental results,the GENRAY code is applied to calculate the propagation and absorption of the lower hybrid wave(LHW) in different configurations.The numerical results show that the variation in the parallel refractive index(N//) between the two configurations is quite large.Transformer recharging experiments were also successfully conducted in EAST.By means of the Karney-Fisch method,the absorption index(α) and the upshift factor of refraction(β) for the LHW are obtained.In addition,the maximum recharging efficiency in EAST is about 4% in the divertor configuration,with a line-averaged electron density of n e av = 0.7 × 10 19 m 3.     

A 4H–SiC betavoltaic battery based on a ~(63)Ni source

A 4H–SiC–~(63)Ni p–n-junction-based betavoltaic battery is investigated. The Monte Carlo method is used to simulate the self-absorption effect of the ~(63)Ni source, the backscattering process, and the transport of beta particles in 4H–SiC material. The main factors that affect the energy conversion efficiencies of the cell are analyzed. Based on the simulation results, it can be calculated that, when the thickness of the ~(63)Ni source increases from 2 ×10~(-3) to10 lm, the theoretical maximum device conversion efficiency increases from 16.77 to 23:51% and the total conversion efficiency decreases from 16.73 to 1:48%.Furthermore, a feasible design with a maximum output power density of 0:36 μW=cm~2 and an optimal device conversion efficiency of 23:5% is obtained.     

Photon and positron production by ultrahigh-intensity laser interaction with various plasma foils

The generation of γ photons and positrons using an ultrahigh-intensity laser pulse interacting with various plasma solid foils is investigated with a series of quantum electrodynamic particlein-cell(PIC) simulations. When ultrahigh-intensity lasers interact with plasma foils, a large amount of the laser energy is converted into γ photon energy. The simulation results indicate that for a fixed laser intensity with different foil densities, the conversion efficiency of the laser to γphotons and the number of produced photons are highly related to the foil density. We determine the optimal foil density by PIC simulations for high conversion efficiencies as approximately 250 times the critical plasma density, and this result agrees very well with our theoretical assumptions. Four different foil thicknesses are simulated and the effects of foil thickness on γ photon emission and positron production are discussed. The results indicate that optimal foil thickness plays an important role in obtaining the desired γ photon and positron production according to the foil density and laser intensity. Further, a relation between the laser intensity and conversion efficiency is present for the optimal foil density and thickness.     

Geant4 simulation of plastic scintillators for a prototype μSR spectrometer

The experimental muon source on China Spallation Neutron Source(CSNS) is expected to be a high intensity(105μ+/s) surface muon source with a small beam spot of 4-cm diameter.For a practical application of this muon source,we are devoting to develop the first pulsed μSR spectrometer in China.In this paper,the performance of plastic scintillators in the μSR spectrometer is studied by Monte Carlo simulation.The processes such as positron energy deposition,scintillation photons production,light propagation and photon-electron conversion are carefully considered.According to the results,an optimal dimension of the plastic scintillator is proposed using for our future spectrometer,which has a long-strip shape with the dimension variation range of 50–60 mm length,5–8 mm height,and 10–12 mm width.Finally,we can build a spectrometer with a count rate up to 104e+/s by 100–120 forward and backward segmental detectors in total.The simulation could serve as an important guide for spectrometer construction.     

Preparation of a new anion exchanger by pre-irradiation grafting technique and its adsorptive removal of rhenium(Ⅶ) as analogue to ~(99)Tc

A new anion exchanger with pyridine groups was prepared by grafting of 2-vinyl pyridine onto polypropylene(PP) nonwoven fabrics by pre-irradiation grafting technique, followed by quaternization of pyridine rings in grafted chains in reaction with bromoethane. The results showed that the grafting yield increased with the monomer concentration and conversion ratio of quaternization increased with the time. The grafted and quaternized fabrics were characterized by FT-IR, DSC, SEM and ICP. The possibility of adsorption of perrhenate(ReO–4), a nonradioactive analogue to pertechnetate(99TcO–4), from aqueous solution by anion exchanger was investigated. The experiments performed at pH= 0.1–6 showed that p H = 2.2 was the optimal acidity for ReO–4adsorption, and an adsorption equilibrium was achieved in 30 min. The reaction enthalpy was-12.55 k J/mol,indicating that the adsorption process is exothermic. XPS tests indicated that the Re O–4uptake was a typical ion exchange between Cl–on anion exchanger and ReO–4.     

Study and Design of a High-Frequency Interaction Cavity for a 140 GHz Megawatts Gyrotron

The gyrotron is one of the most promising high-power millimeter-wave sources for electron cyclotron resonance heating(ECRH) in controlled thermal nuclear fusion experiments.In this paper,the design of a high-frequency interaction cavity of a 1 MW/140 GHz gyrotron is described in detail.The cavity is designed by using eigen mode analysis and radio frequency(RF) behavior calculation.Rounded transitions at the input and output tapers are designed for reducing mode conversion.With the obtained cavity structure,non-linear self-consistent equations are adopted to calculate its output power and efficiency.A particle-in-cell(PIC) method is used to simulate the beam-wave interaction process for obtaining the resonant frequency and output power of the cavity.The PIC simulation results match considerably well with the results obtained by the non-linear self-consistent calculation.The cavity is currently under construction and will be integrated with other components for overall testing.     

Data decomposition method for full-core Monte Carlo transport–burnup calculation

Monte Carlo transport simulations of a full-core reactor with a high-fidelity structure have been made possible by modern-day computing capabilities. Performing transport–burnup calculations of a full-core model typically includes millions of burnup areas requiring hundreds of gigabytes of memory for burnup-related tallies. This paper presents the study of a parallel computing method for full-core Monte Carlo transport–burnup calculations and the development of a thread-level data decomposition method. The proposed method decomposes tally accumulators into different threads and improves the parallel communication pattern and memory access efficiency. A typical pressurized water reactor burnup assembly along with the benchmark for evaluation and validation of reactor simulations model was used to test the proposed method.The result indicates that the method effectively reduces memory consumption and maintains high parallel efficiency.     

NO_x storage and reduction assisted by non-thermal plasma over Co/Pt/Ba/γ-Al_2O_3 catalyst using CH_4 as reductant

N_Ox storage and reduction(NSR) technology has been regarded as one of the most promising strategies for the removal of nitric oxides(NO_x) from lean-burn engines, and the potential of the plasma catalysis method for NO_x reduction has been confirmed in the past few decades. This work reports the NSR of nitric oxide(NO) by combining non-thermal plasma(NTP) and Co/Pt/Ba/γ-Al_2O_3(Co/PBA) catalyst using methane as a reductant. The experimental results reveal that the NO_x conversion of NSR assisted by NTP is notably enhanced compared to the catalytic efficiency obtained from NSR in the range of 150 °C–350 °C, and NO_x conversion of the 8% Co/PBA catalyst reaches 96.8% at 350°C. Oxygen(O_2) has a significant effect on the removal of NO_x, and the NO_x conversion increases firstly and then decreases when the O_2 concentration ranges from 2% to 10%. Water vapor reduces the NO_x storage capacity of Co/PBA catalysts on account of the competition for adsorption sites on the surface of Co/PBA catalysts. There is a negative correlation between sulfur dioxide(SO_2) and NO_x conversion in the NTP system, and the 8% Co/PBA catalyst exhibits higher NO_x conversion compared to other catalysts, which shows that Co has a certain SO_2 resistance.     

Electromagnetic–thermal–structural coupling analysis of the ITER edge localized mode coil with flexible supports

In a fusion reactor, the edge localized mode(ELM) coil has a mitigating effect on the ELMs of the plasma. The coil is placed close to the plasma between the vacuum vessel and the blanket to reduce its design power and improve its mitigating ability. The coil works in a high-temperature,high-nuclear-heat and high-magnetic-field environment. Due to the existence of outer superconducting coils, the coil is subjected to an alternating electromagnetic force induced by its own alternating current and the outer magnetic field. The design goal for the ELM coil is to maintain its structural integrity in the multi-physical field. Taking as an example the middle ELM coil(with flexible supports) of ITER(the International Thermonuclear Fusion Reactor), an electromagnetic–thermal–structural coupling analysis is carried out using ANSYS. The results show that the flexible supports help the three-layer casing meet the static and fatigue design requirements. The structural design of the middle ELM coil is reasonable and feasible. The work described in this paper provides the theoretical basis and method for ELM coil design.     

The Design and Optimization of a Neutron Time-of-Flight Spectrometer with Double Scintillators for Neutron Diagnostics on EAST

Neutron energy spectrometry diagnosis plays an important role in magnetic con-finement fusion.A new neutron time-of-flight (TOF) spectrometer with double scintillators is designed and optimized for the EAST tokamak.A set of optimal parameters is obtained by Monte Carlo simulation,based on the GEANT4 and ROOT codes.The electronic setup of the measurement system is designed.The count rate capability is increased by introducing a flash ADC.The designed spectrometer with high resolution and efficiency is capable of being applied to fusion neutron diagnostics.Applications in mixed-energy and continuous energy neutron fields can also be considered.     

一种复合型核电池的理论设计

在各类核电池中,直接接收型核电池的结构最简单,但其效率不高。部分原因在于很多带电粒子反向发射,被发射极自吸收而产生废热。考虑到如何把燃料产生的废热利用起来,设计了一种复合型核电池的结构,即在直接接收型核电池结构的基础上,加上热电转换装置,把直接接收型核电池产生的废热转换为电,进而可以明显地提高整个电池1%左右的效率。     

Electron Heating in Tokamak LHCD Experiment

1.IntroductionThemainpurposeoflowerhybridcurrentdrive(LHCD)istodrivetoroidalcurrentformaintaininglongpulsedischarge.However,thepowerlevelrequiredforthispurposeiscomparablewiththatusedforplasmaheatingbothinexperimentaldevicesorinreactors.ThepowerbalanceduringLHCDisthenaproblemneedfultobeidentified.OtherthantheLandaudampingwhichisthemainmechanismfordrivingtoroidalcurrent,thecollisionalheatingthroughelectroncollisionwiththebackgroundionsorimpuritiesisafundamentalprocesstodissipatethewavepower…     

Investigation of operating parameters on CO2 splitting by dielectric barrier discharge plasma

Experiments of CO2 splitting by dielectric barrier discharge (DBD) plasma were carried out,and the influence of CO2 flow rate,plasma power,discharge voltage,discharge frequency on CO2 conversion and process energy efficiency were investigated.It was shown that the absolute quantity of CO2 decomposed was only proportional to the amount of conductive electrons across the discharge gap,and the electron amount was proportional to the discharge power;the energy efficiency of CO2 conversion was almost a constant at a lower level,which was limited by CO2 inherent discharge character that determined a constant gap electric field strength.This was the main reason why CO2 conversion rate decreased as the CO2 flow rate increase and process energy efficiency was decreased a little as applied frequency increased.Therefore,one can improve the CO2 conversion by less feed flow rate or larger discharge power in DBD plasma,but the energy efficiency is difficult to improve.     

半导体器件在辐射作用下的电学输出性能研究

半导体结型器件是决定辐射伏特效应同位素电池能量转换效率的核心部件。采用加速器产生的不同能量电子束和63Ni源的β射线对硅基PIN结型器件进行辐照,在线测量了其电学输出性能。当电子束能量为18 keV,可得到大于4%的能量转换效率;电子束能量为6 keV,能量转换效率在0.16%～0.33%之间; 活度2.96×108 Bq的63Ni源片辐照的能量转换效率为0.1%左右。     

14 MeV快中子照相用光纤转换屏研究

快中子照相技术因其超强的样品透视能力而成为射线无损检测技术近年来研究的热点,转换屏是中子照相装置的关键部件。光纤转换屏是一种新型的快中子照相转换屏,较大程度兼顾了光纤阵列的高探测效率和荧光屏的高成像质量,具有很好的应用前景。本文以D-T加速器为中子源,用ZnS和环氧树脂以及光纤研制了快中子照相光纤转换屏,耦合科学级CCD数字成像系统,进行了快中子数字照相技术研究,获取了不同光纤排列方式的光纤转换屏积分曝光图像,同时测量了快中子荧光屏和塑料闪烁体等其他快中子照相用转换屏的发光效率,实验结果表明,光纤转换屏的发光效率高于其他类型转换屏的。     

气馈式碱金属热电转换装置性能分析方法

为促进气馈式碱金属热电转换装置（AMTEC）的设计与性能评价,基于气馈式AMTEC压力模型、电模型、热模型,开发了气馈式AMTEC热电转换性能分析程序,以SAIRS-C空间电源中AMTEC模块作为计算对象,计算其输出电功率、热电转换效率、负荷跟踪特性等性能参数。结果表明,该方法所得输出电功率、热电转换效率参数与文献曲线变化趋势基本一致,但负荷跟踪特性等计算值与文献值存在一定偏差。该方法适用于气馈式AMTEC元件性能分析与评价,应用于元件设计时,程序需进一步改进。     

Experimental results from a beam direct converter at 100 kV

A direct-energy converter was developed for use on neutral-beam injectors. The purpose of the converter is to raise the efficiency of the injector by recovering the portion of the ion beam not converted to neutrals. In addition to increasing the power efficiency, direct conversion reduces the requirements on power supplies and eases the beam dump problem. The converter was tested at Lawrence Berkeley Laboratory on a reduced-area version of a neutral-beam injector developed for use on the Tokamak Fusion Test Reactor at Princeton. The conversion efficiency of the total ion power was 65 ±7% at the beginning of the pulse, decaying to just over 50% by the end of the 0.6-s pulse. Once the electrode surfaces were conditioned, the decay was due to the rise in pressure of only the beam gas and not to outgassing. The direct converter was tested with 1.7 A of hydrogen ions and with 1.5 A of helium ions through the aperture with similar efficiencies. At the midplane through the beam, the line power density was 0.7 MW/m, for comparison with our calculations of slab beams and the prediction of 2–4 MW/m in some reactor studies. Over 98 kV was developed at the ion collector when the beam energy was 100 keV. When electrons were suppressed magnetically, rather than electrostatically, the efficiency dropped to 40%. However, a better designed electron catcher could improve this efficiency. New electrode material released gas (mostly H₂ and CO) in amounts that exceeded the input of primary gas from the beam. The electrodes were all made of 0.51-mm-thick molybdenum cooled only by radiation. This allowed the heating by the beam to outgas the electrodes and for them to stay hot enough to avoid the reabsorption of gas between shots. By minor redesign of the electrodes, adding cryopanels near the electrodes, and grounding the ion source, these results extrapolate with high confidence to an efficiency of 70–80% at a power density of 2–4 MW/m. Higher power may be possible with magnetic electron suppression.     

动态膜电解制备四价铀中电流效率的讨论

进行了不同电流密度（40～160 mA/cm²）下电解制备四价铀的研究。研究结果表明,采用动态膜电解制备四价铀,能在保证六价铀转化率的前提下维持较高的电流效率,最终保证了四价铀制备过程的高效率。但在电解过程后期（大部分六价铀已转化为四价铀）,若采用高电流密度,电流效率迅速下降,而采用低电流密度时仍能维持较高的电流效率。为进一步提高四价铀制备过程的电流效率,研究了程序控制电流密度阶梯减小的电解方式对电解过程后期的电流效率的影响。研究结果表明,与恒定电流密度电解方式相比,采用阶梯形减小电流密度的电解方式,可有效地提高电解过程的电流效率,有助于减少副反应的发生。     

Plasma-chemical Synthesis and Regeneration of Catalysts for CH4 Steam Conversion

We carried out experimental studies concerning the plasma-chemical synthesis(PCS) of a catalyst for CH4 steam conversion and designed and built the equipment for PCS and/or regeneration of spent catalyst for CH4 steam conversion .Under the conditions of an electric-arc low-temperature plasma(LTP),we studied the Ni-O-Al system and performed a comprehensive physicochemical analysis of the ultradispersed product obtatined .It‘s the first time worldwide when the conditions of plasma-chemical synthesis and /or regeneration of CH4 steam coversion catalysts under the conditions of electric-are LTP are investigated depending on the plasma-chemical process (PCP) paracmeters and the plasma-chemical reactor (PCP) TYPE (with CW-“cold walls“ TW=500K or WW-“warm walls“ TW=1500K),samples with a specific surface of 120 m^2/g are obtained.Plasma-chemically synthesized and/ or regenerated samples have a homogenous chemical composition similar to that the Girdller (USA) convertional industrial catalyst.It is empirically established that the optimal temperature range in PCR for synthesis of samples with maximum dispersity is (2000-3000)k.Results from inverstigation on dynamics and kindetics of plasma-chemically synthesized and /or regenerated catalysts for CH4 steam conversion slow that under LTP conditions premises for the formation of catalyst compositions are established.They are reduced 3 to 4 times faster than their industrial analogues.High specific surface of the samples ,homogenous composition,high rate of active chemical surface formed by reduction, faulty craystal lattice of catalytically active phases and mostly high catalytic activity make them a potential competitor tiwh their industrial analogues for their probable production in catalyst shops.