The research progress of an E//B neutral particle analyzer

An E//B neutral particle analyzer(NPA)has been designed and is under development at Sichuan University and Southwestern Institute of Physics.The main purpose of the E//B NPA is to measure the distribution function of fast ions in the HL-2A/3 tokamak.The E//B NPA contains three main units,i.e.the stripping unit,the analyzing unit and the detection unit.A gas stripping chamber was adopted as the stripping unit.The results of the simulations and beam tests for the stripping chamber are presented.Parallel electric and magnetic fields provided by a NdFeB permanent magnet and two parallel electric plates were designed and constructed for the analyzing unit.The calibration of the magnetic and electric fields was performed using a 50 kV electron cyclotron resonance ion source(ECRIS)platform.The detection unit consists of 32lutetium-yttrium oxyorthosilicate(LYSO)detector modules arranged in two rows.The response functions ofα,hydrogen ions(H^(+),H_(2)^(+)and H_(3)^(+))andγfor a detector module were measured with^(241)Am,^(137)Cs and^(152)Eu sources together with the 50 kV ECRIS platform.The overall results indicate that the designed E//B NPA device is capable of measuring the intensity of neutral hydrogen and deuteron atoms with energy higher than 20 keV.

Discharge mode and particle transport in radio frequency capacitively coupled Ar/O_(2) plasma discharges

Simulations are conducted on capacitively coupled Ar/O_(2)mixed gas discharges employing a one-dimensional fluid coupled with an electron Monte Carlo(MC)model.The research explores the impact of different O_(2)ratio and pressures on the discharge characteristics of Ar/O_(2)plasma.At a fixed Ar/O_(2)gas ratio,with the increasing pressure,higher ion densities,as well as a slight increase in electron density in the bulk region can be observed.The discharge remains dominated by the drift-ambipolar(DA)mode,and the flux of O(3P)at the electrode increases with the increasing pressure due to higher background gas density,while the fluxes of O(1D)and Ardecrease due to the pronounced loss rate.With the increasing proportion of O_(2),a change in the dominant discharge mode from a mode to DA mode can be detected,and the O_(2)-associated charged particle densities are significantly increased.However,Ar+density shows a trend of increasing and then decreasing,while for neutral fluxes at the electrode,Arflux decreases,and O(3P)flux increases with the reduced Ar gas proportion,while trends in O(1D)flux show slight differences.The evolution of the densities of the charged particle and the neutral fluxes under different discharge parameters are discussed in detail using the ionization characteristics as well as the transport properties.Hopefully,more comprehensive understanding of Ar/O_(2)discharge characteristics in this work will provide a valuable reference for the industry.

Proton pitch angle distributions in the Martian induced magnetosphere: A survey of Tianwen-1 Mars Ion and Neutral Particle Analyzer observations

The pitch angle distributions of ions and electrons can be affected by various processes;thus,they can serve as an important indicator of the physical mechanisms driving the dynamics of space plasmas.From observations from the Mars Ion and Neutral Particle Analyzer onboard the Tianwen-1 orbiter,we calculated the pitch angle distributions of protons in the Martian induced magnetosphere by using information from the magnetohydrodynamically simulated magnetic field,and we statistically analyzed the spatial occurrence pattern of different types of pitch angle distributions.Even though no symmetrical features were seen in the dataset,we found the dominance of the field-aligned distribution type over the energy range from 188 to 6232 eV.Maps of the occurrence rate showed the preferential presence of a trapped-like distribution at the lower altitudes of the surveyed nightside region.Although our results are more or less restricted by the adopted magnetic field,they indicate the complexity of the near-Mars proton pitch angle distributions and infer the possibility of wave–particle interactions in the Martian induced magnetosphere.

A simulation study of a windowless gas-stripping room in an E//B neutral particle analyzer

The neutral particle analyzer(NPA)is one of the crucial diagnostic devices in a Tokamak facility.The stripping unit is one of the main parts of the NPA.A windowless gas-stripping room with two differential pipes has been constructed in a parallel electric and magnetic fields(E//B)NPA.The pressure distributions in the stripping chamber are simulated by ANSYS Fluent together with MolFlow+.Based on the pressure distributions obtained from the simulation,the stripping efficiency of the E//B NPA is studied using GEANT4.Hadron reaction physics is modified to track the charge state of each particle in a cross-section-based method in GEANT4.The transmission rates(R)and stripping efficiencies f_(+1)are examined for particle energies ranging from 20 to 200 keV with the input pressure(P_(0)),ranging from 20 to 400 Pa.According to the combined global efficiency,R×f_(+1),P_(0)=240 Pa is obtained as the optimum pressure for the maximum global efficiency in the incident energy range investigated.

Neutral Particle Transport in Cylindrical Plasma Simulated by a Monte Carlo Code

A Monte Carlo code （MCHGAS） has been developed to investigate the neutral particle transport. The code can calculate the radial profile and energy spectrum of neutral particles in cylindrical plasmas. The calculation time of the code is dramatically reduced when the Splitting and Roulette schemes are applied. The plasma model of an infinite cylinder is assumed in the code, which is very convenient in simulating neutral particle transports in small and middle-sized tokamaks. The design of the multi-channel neutral particle analyser （NPA） on HL-2A can be optimized by using this code.

Neutralized solar energetic particles for SEP forecasting:Feasibility study of an innovative technique for space weather applications

Energetic neutral atoms(ENAs)are produced by the neutralization of energetic ions formed by shock-accelerated gradual solar energetic particle events(SEP).These high-energy ENAs(HENAs)can reach the Earth earlier than the associated SEPs and thus can provide information about the SEPs at the lower corona.The HENA properties observed at Earth depend on the properties of the coronal mass ejection(CME)-driven shocks that accelerate the SEPs.Using a model of HENA production in a shock-accelerated SEP event,we semi-quantitatively investigate the energy-time spectrum of HENAs depending on the width,propagation speed,and direction of the shock,as well as the density and ion abundances of the lower corona.Compared to the baseline model parameters,the cases with a wider shock width angle or a higher coronal density would increase the HENA flux observed at the Earth,while the case with an Earthpropagating shock shows a softened HENA spectrum.The comparison of expected HENA fluxes in different cases with a flight-proven ENA instrument suggests that solar HENAs can feasibly be monitored with current technologies,which could provide a lead time of 2−3 hours for SEPs at a few MeV.We propose that monitoring of solar HENAs could provide a new method to forecast shock-driven SEP events that are capable of significant space weather impacts on the near-Earth environment.

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

Neutral particle energy spectra in the HT-7 tokamak are calculated by using the Monte Carlo method. It can reproduce the spectra measured in experiment. Differences of neutral particle energy spectra in higher and lower electron density plasma are discussed. Results show that the ion temperature given by neutral particle energy spectra is lower than the real ion temperature, but the deviation is within 10% if the ion temperature is less than 800 eV and thecentral chord-averaged electron density does not exceed 3 ×1013 cm-3. But for ion temperature higher than 1000 eV at the central chord-averaged density limit up to 5 ×1013 cm-3, the neutral particle energy spectra can still give the ion temperature within 10% deviation.

High Speed Image Acquisition ＆ Neutral Particle Count Systems and the RTX Research

In HL-2A tokamak experiment, high speed image acquisitoin system grabs images and shows them in real-time. It provides serial images of discharge to help scientists a lot to analyse the experiment. Neutral particle count system counts the number of neutral particles radiated from fusion plasmas. It provides the data to calculate the ion energy.

PRODUCTION IN PICHIAPASTORISAND CHARACTERIZATION OF GENETIC ENGINEERED CHIMERIC HBV/HEV VIRUS-LIKE PARTICLES

Objective To investigate the presentation of a neutralization epitope-containing peptide antigen of hepatitis E virus (HEV) on chimeric virus-like particles (VLPs) of hepatitis B surface antigen (HBsAg). MethodsThe gene fragment corresponding to amino acids (aa) 551-607 (HEnAg) of HEV capsid protein, which contains the only neutralization epitope identified to date, was fused via a synthetic glycine linker in frame with the gene of HBsAg. The resulted fusion gene was then integrated through transformation into the genome of Pichiapastorisunder the control of a methanol-induced alcohol oxidase 1 (AOX1) promoter and expressed intracellularly. The expression products in the soluble cell extracts were characterized by Western blot, ELISA, CsCl density gradient analysis, and electron microscopic visualiza-tion. Results The novel fusion protein incorporating HBsAg and the neutralization epitope-containing HEnAg was expressed successfully in Pichiapastoriswith an expected molecular weight of approximately 32 kD. It was found to possess the ability to assemble into chimeric HBV/HEV VLPs with immunological, physical and morphological characteristics akin to HBsAg particles. Not only did the chimeric VLPs show high activity levels in a HBsAg particle-specific ELISA but they were also strongly immunoreactive with hepatitis E (HE) positive human serum in a HEV specific ELISA, indicating that HEnAg peptide fragments were exposed on VLP surfaces and would be expected to be readily accessible by cells and molecules of the immune system. Similarity between chimeric VLPs to highly immunogenic HBsAg particles may confer good immuno-genicity on surface-displayed HEnAg. Conclusion The chimeric HBV/HEV VLPs produced in this study may have potential to be a recombinant HBV/HEV bivalent vaccine candidate.

A Virus-type Specific Serological Diagnosis of Flavivirus Infection Using Virus-like Particles

Many flaviviruses are emerging and reemerging pathogens, such as West Nile virus （WNV）, dengue virus （DENV）, yellow fever virus （YFV）, and Japanese encephalitis virus. Serological assay is the dominant method for diagnosis of flavivirus infections in human. Because antibodies generated during flavivirus infections cross-react with other flavivirus members, plaque reduction neutralization test （PRNT） is the only available assay to determine the infecting flavivirus type. Since PRNT requires culturing raw viruses, it must be performed in biosafety levet-3 or level-4 containment for many flaviviruses, and takes more than ten days to complete. To overcome these problems, we have developed flavivirus viral-like particles （VLPs） that could be used to replace raw viruses in the neutralization assay. The VLPs were prepared by trans packaging a luciferase-reporting replicon with viral structural proteins. This novel assay involves three simple steps： （i） VLPs from a panel of flaviviruses are incubated with flavivirus-infected sera at 37℃ for 1 h; （ii）the neutralized VLPs are used to infect Vero cells; and （iii） the infected cells are measured for luciferase activities at 22 h post-infection. The virus type whose VLP is most efficiently neutralized by the serum specimen （as quantified by the luciferase activities） is the etiologic agent. As a proof-of-concept, we show that a WNV-infected mouse serum neutralized the WNV VLP more efficiently and selectively than the DENV and YFV VLPs. Our results demonstrate that the VLP neutralization assay maintains the ＂gold standard＂ of the classic PRNT; importantly, it shortens the assay time from 〉10 days to 〈1 day, and can be performed in biosafety level-2 facility.

Efficient Humoral and Cellular Immune Responses Induced by a Chimeric Virus-like Particle Displaying the Epitope of EV71 without Adjuvant

Objective To eliminate the side effects of aluminum adjuvant and His-tag,we constructed chimeric VLPs displaying the epitope of EV71（SP70） without His-tagged.Then evaluating whether the VLPs could efficiently evoke not only humoral but also cellular immune responses against EV71 without adjuvant.Methods The fusion protein was constructed by inserting SP70 into the MIR of truncated HBc Ag sequence,expressed in E.Coli,and purified through ion exchange chromatography and density gradient centrifugation.Mice were immunized with the VLPs and sera were collected afterwards.The specific antibody titers,Ig G subtypes and neutralizing efficacy were detected by ELISA,neutralization assay,and EV71 lethal challenge.IFN-γ and IL-4 secreted by splenocytes were tested by ELISPOT assay.Results HBc-SP70 proteins can self-assemble into empty VLPs.After immunization with HBc-SP70 VLPs,the detectable anti-EV71 antibodies were effective in neutralizing EV71 and protected newborn mice from EV71 lethal challenge.There was no significant difference for the immune efficacy whether the aluminum adjuvant was added or not.The specific Ig G subtypes were mainly IgG1 and IgG2 b and splenocytes from the mice immunized produced high levels of IFN-γ and IL-4.Conclusion The fusion proteins without His-tagged was expressed and purified as soluble chimeric HBc-SP70 VLPs without renaturation.In the absence of adjuvant,they were efficient to elicit high levels of Th1/Th2 mixed immune response as well as assisted by aluminum adjuvant.Furthermore,the chimeric VLPs have potential to prevent HBV and EV71 infection simultaneously.

Particle swarm optimization and its application to seismic inversion of igneous rocks

In order to improve the fine structure inversion ability of igneous rocks for the exploration of underlying strata, based on particle swarm optimization(PSO), we have developed a method for seismic wave impedance inversion. Through numerical simulation, we tested the effects of different algorithm parameters and different model parameterization methods on PSO wave impedance inversion, and analyzed the characteristics of PSO method. Under the conclusions drawn from numerical simulation, we propose the scheme of combining a cross-moving strategy based on a divided block model and high-frequency filtering technology for PSO inversion. By analyzing the inversion results of a wedge model of a pitchout coal seam and a coal coking model with igneous rock intrusion, we discuss the vertical and horizontal resolution, stability and reliability of PSO inversion. Based on the actual seismic and logging data from an igneous area, by taking a seismic profile through wells as an example, we discuss the characteristics of three inversion methods, including model-based wave impedance inversion, multi-attribute seismic inversion based on probabilistic neural network(PNN) and wave impedance inversion based on PSO.And we draw the conclusion that the inversion based on PSO method has a better result for this igneous area.

Particle-in-cell simulation for effect of anode temperature on discharge characteristics of a Hall effect thruster

Propellant gas flow has an important impact on the ionization and acceleration process of Hall effect thrusters （HETs）. In this paper, a particle-in-cell numerical method is used to study the effect of the anode temperature, i.e., the flow speed of the propellant gas, on the discharge characteristics of a HET. The simulation results show that, no matter the magnitude of the discharge voltage, the calculated variation trends of performance parameters with the anode temperature are in good agreement with the experimental ones presented in the literature. Further mechanism analysis indicates that the magnitude of the electron temperature is responsible for the two opposing variation laws found under different discharge voltages. When the discharge voltage is low, the electron temperature is low, and so is the intensity of the propellant ionization; the variation of the thruster performance with the anode temperature is thereby determined by the variation of the neutral density that affects the propellant utilization efficiency. When the discharge voltage is high, the electron temperature is large enough to guarantee a high degree of the propellant utilization no matter the magnitude of the anode temperature. The change of the thruster performance with the anode temperature is thus dominated by the change of the electron temperature and consequently the electron-neutral collisions as well as the electron cross-field mobility that affect the current utilization efficiency.

Estimate Totel Number of the Earth Atmospheric Particle with Standard Atmosphere model

The total number of atmospheric particle (AP) is an important datum for planetary science and geoscience. Estimating entire AP number is also a familiar question in general physics. With standard atmosphere model, considering the number difference of AP caused by rough and uneven in the earth surface below, the sum of dry clean atmosphere particle is . So the whole number of AP including water vapor is . The rough estimation for the total number of AP on other planets (or satellites) in condensed state is also discussed on the base of it.

中性粒子分析仪的研究现状

中性粒子分析仪(NPA)作为托卡马克(Tokamak)装置的重要诊断工具,在等离子体物理研究中具有重要科学意义和广泛应用前景。NPA通过精确测量从等离子体中逃逸的中性粒子,可获取等离子体内部的关键信息,包括离子温度、快离子能谱分布和氢同位素比例等。自20世纪60年代首台NPA问世以来,经过60余年的技术发展,其诊断能力已经实现了质的飞跃,并且发展出了多种类型的NPA。针对中国环流3号(HL-3)装置的快离子物理研究,四川大学与核工业西南物理研究院联合研制了基于LYSO+SiPM探测器的串联式平行电磁场结构的NPA(E//B NPA)。该E//B NPA已安装到HL-3装置,并在等离子体放电实验中成功测量到高能量氘(D)中性粒子能谱,为今后HL-3装置中性粒子诊断及快离子研究奠定了坚实的技术基础。

中性地浸采铀全流程溶液中颗粒粒径分布及过滤建议

掌握中性地浸采铀全流程溶液中颗粒大小,对调控浸出过程、优选过滤器、确定除固位置、缓解矿层堵塞、恢复抽注液量和减轻树脂床层板结等具有指导意义。以内蒙古纳岭沟矿床中性地浸采铀全流程溶液为对象,基于激光粒度仪测试数据,获取了全流程溶液中颗粒粒径分布规律。结果表明,浸出液中颗粒粒径频率分布曲线呈非对称性,累计分布曲线呈“S”型,粒径分布范围窄,最大颗粒粒径<100μm;树脂床层对颗粒物有较强的过滤作用,吸附尾液过滤器的滤袋精度应根据树脂粒径大小和系统压力确定;中性体系中加入的O 2或CO 2对颗粒粒径影响微弱;淋洗合格液和沉淀罐中母液的颗粒粒径频率分布曲线均呈“双峰”型,贫液中颗粒粒径频率则呈正态分布;母液槽中颗粒最大粒径约为40μm。建议该矿床原液袋式过滤器的滤袋精度选用10~50μm,同时在母液槽与淋洗剂配制罐之间增加10~20μm精度的过滤器。

基于PSO-CNN-LSTM的短期热负荷预测模型

为提高短期供热负荷预测精度,减少供热不均与供需失调所造成的能源浪费,提出一种基于粒子群(Particle swarm optimization,PSO)、经验模态分解(Empirical Mode Decomposition,EMD)、卷积神经网络(Convolutional Neural Network,CNN)和长短时记忆神经网络(Long Short Term Memory Network,LSTM)的混合预测模型。首先,针对供热负荷呈现非线性、复杂性等特点,采用EMD对供热负荷分解,从而实现弱化供热负荷复杂程度;其次,分别运用CNN与LSTM提取供热负荷空间特征与时域特征;最后,结合PSO算法对LSTM网络的超参数进行调整,寻找出最优参数。实验表明,结合EMD分解的PSOCNN-LSTM网络相比LSTM、CNN-LSTM、EMD-CNN-LSTM平均误差分别降低了44%、34%、24%、21%,拥有更高的预测精度和拟合效果。所提模型为集中供热负荷预测提供了一种新的思路,对于制定集中供热能源分配提供了参考意义。

基于多偶极腔体的氦灰激光诱导荧光诊断实验验证研究

利用多偶极腔体模拟聚变堆偏滤器附近氦中性粒子存在环境,通过激光诱导荧光诊断对于氦中性粒子的速度分布谱进行了直接测量,对测量区域的波长标定以及二极管激光器的可调谐范围的拓宽进行了研究。对该方案在聚变堆上的应用进行了评估。

Regime Map of Dry Neutralization Agglomeration Process Containing Non-Reactive Ingredient on a Laboratory Scale

This study described a regime map for dry neutralization agglomeration. Based on the map, the effects of selected key parameters, such as ingredient composition, operation temperature, agitation speed, and size of Na_2CO_3 particles, were investigated using a laboratory-scale mixer, and properties of the agglomeration product were analyzed, including particle size distribution, Hunter color, and flowability. Torque curves evolving during the process were correlated with the system flowability. Three distinguishable regimes were indicated, dry, wet, and transitional, and the agitation speed was found to have a different influence on the agglomeration process for the three regimes. Furthermore, the influence of temperature on reactive agglomeration significantly differed from that in agglomeration processes in which the binder was non-reactive.