基于EAST束发射光谱的中性束衰减特征研究

中性束注入(NBI)是托卡马克装置重要的辅助加热与电流驱动手段,中性原子的离化是决定中性束的加热(能量和粒子沉积剖面)和电流驱动效率的关键环节。通常情况下,利用背景等离子体参数与中性束参数模拟计算快的中性粒子与等离子体的离化,即中性束沉积过程,进而分析托卡马克中性束加热和电流驱动效果。束发射光谱是高能中性粒子注入等离子体后,与等离子体的电子、离子发生碰撞激发,中性粒子退激发过程中产生的一系列特征谱线,其束发射光谱强度受等离子体密度、温度、束能量、束密度等因素影响,可以利用束发射光谱强度变化研究中性束的衰减特性。在EAST托卡马克上通过实验测量中性束粒子与等离子体碰撞激发的光谱强度,分析得到了中性束在不同等离子体密度以及不同中性束能量下的衰减特性,并采用主动束光谱仿真与数值分析软件(SOS)进行了相应的模拟计算,研究表明实验测量与模拟计算结果两者具有较好的一致性,这验证了通过实验测量束发射光谱获取中性束衰减特征的可行性。

EAST装置等离子体放电真空室抽气系统抽速标定及应用

真空系统是聚变装置的重要组成部分,EAST真空系统包括等离子体放电真空室和低温超导真空室。等离子体放电真空室又称内真空室。内真空室抽气系统直接影响装置的粒子排出,关系到高参数等离子体放电获得。EAST装置升级改造后的内真空室抽气系统主要包括主抽管道抽气子系统、偏滤器抽气子系统和低杂波加热系统抽气子系统,整个抽气系统使用了6台分子泵、14台外置低温泵和2套内置低温泵。采用粒子平衡的方法,对内真空室抽气系统各子系统进行了抽速标定。实验结果表明,最佳抽气性能区间在5×10^(-4)~5×10^(-3)Pa,并且随着真空室压力增大或者减小,各子系统的抽气速率均下降。对比改进前后的内真空室抽气系统的总抽速,改进后的最大抽速可达170 m^(3)/s,总体抽气速率提升20%左右。在百秒量级等离子放电参数下,利用标定的抽气速率数据初步评估了燃料粒子的滞留情况。本研究为等离子体放电的壁滞留与再循环控制以及其他相关物理实验开展提供了数据支持。

FAR3d程序对EAST上阿尔芬不稳定性识别过程中的应用

为更好理解EAST实验中的等离子体不稳定性现象,文章从实验和模拟两个角度,对EAST中高βN放电区间的阿尔芬不稳定性现象进行了分析。在实验上,本文使用高频磁探针和电子回旋辐射诊断对不稳定性的频率、位置、环向模数进行判断。在模拟上首次应用了FAR3d程序,识别了在ρ=0.45、频率为87 kHz的主导模式TAE(toroidicity-induced Alfven eigenmode),以及ρ=0.55、频率为62 kHz的次主导模式EPM(energetic particle mode),环向模数均为2,与实验中的测量结果对比在误差范围内基本一致,自洽地识别了不稳定性的类型并且得到了位置与频率信息。在此基础上,对有限拉莫轨道(finite Larmor radius, FLR)效应进行评估。模拟结果显示,在EAST高βN放电区间,FLR效应对识别低环向模数n的不稳定性模式的影响较小。在该放电的模式的识别过程中可关闭FLR以加速计算。FAR3d程序高效的计算能力和精准的模拟结果,可为后续EAST的实验提供指导。

EAST 低杂波加热对同向切向中性束碰撞力矩影响的研究

为研究低杂波加热对同向切向中性束注入的束功率沉积和碰撞力矩的影响,基于低杂波加热的实验参数,使用TRANSP程序进行了模拟分析。研究结果表明,当注入功率1.3MW、能量50keV的同向切向束时,随着LHW加热束沉积功率降低,快离子电荷交换损失增加20%;离子吸收的功率占总的束沉积功率的比例由45%增加到51%。碰撞力矩与束沉积功率的比值由1.327Nm·MW^(-1)增加到1.457Nm·MW^(-1);等离子体电子温度越高,电荷交换损失和碰撞力矩与束沉积功率比值也越大,而低杂波加热期间的束碰撞力矩保持稳定。

EAST装置上差分抽气测量系统的设计

在托卡马克装置运行过程中,装置内壁吸附的杂质粒子会释放到内真空室,影响等离子体的平稳运行。因此需要在放电前对装置进行壁处理清洗。设计了差分抽气测量系统,可以在保持内真空室气体比例不变的前提下降低压力,实现四极质谱仪的正常工作,检测壁处理清洗期间的气体成分。整个设计过程围绕关键部件小流导法兰的流导设计展开,采用粒子平衡法计算得出小流导法兰的设计参数。可以在分子流流态下将待测腔室的气压从10 Pa降低至约0.01 Pa。设计结果为类似高压力条件下气体成分监测设备的设计提供参考。

EAST托卡马克早期H模实验边界局域模特征的统计分析

为分析EAST托卡马克早期(2010—2014年)高约束运行模式(H模)中边界局域模(ELM)与哪些参数具有强相关性,在验证有效性的基础上,采用主打击点处Dα辐射的相对涨落来定量表征边界局域模幅度,建立EAST托卡马克早期H模下ELM特征数据库。统计分析表明,ELM频率随边界安全因子的增大而减小,2010年type-ⅢELM的频率随总加热功率的增大而增大。这与其他装置或2015年以后EAST装置上得到的结果不一致,部分原因是碳杂质水平的变化。碳杂质水平是影响EAST托卡马克早期H模实验中ELM行为的重要因素之一。

EAST托卡马克钨杂质上下不对称性分布的实验研究

基于EAST托卡马克装置高性能极紫外空间分辨杂质光谱仪,本文首次开展了磁约束聚变装置高Z杂质上下不对称分布的实验研究.实验结果显示,在同向中性束注入期间,等离子体芯部环向旋转速度V_(t0)大,钨杂质上下不对称性较强,且辐射(密度)较强的一侧背离离子B×▽B漂移方向;当从上外偏滤器充气口注入氘化甲烷气体后,V_(t0)迅速下降,原有上下不对称性发生反转.因此我们针对近似条件下W^(32+)杂质离子特征线辐射不对称因子I_(u)/I_(d)与V_(t0)依赖关系开展了进一步的统计分析.结果表明,I_(u)/I_(d)正相关于V_(t0),当V_(t0)<20 km/s以下时,不对称性发生反转.上述现象从实验角度验证了漂移动理学的理论预测,说明环向旋转带来的离心力影响了杂质离子平行于磁场方向的动量守恒,作为直接诱因,造成了高Z杂质密度的上下不对称分布,进而影响辐射的分布.本文对钨杂质上下不对称性分布的实验观测为进一步开展高Z杂质极向输运的机理研究打下了坚实的基础,并为今后聚变堆高Z杂质控制提供重要的参考.

基于JWT的EAST实验数据用户身份和服务权限认证

用户身份和服务权限认证已成为身份验证和数据访问安全的重要手段。用户身份认证采用动态令牌技术JWT实现。针对JWT丢失和被截获的问题,提出加密存储、解密使用的策略和IP与JWT绑定机制。根据EAST实验数据和用户的现状,将用户资源划分为二级用户,将服务资源划分为三级资源,采用图数据库Neo4j存储用户和资源之间的权限关系,并提出位图法加速权限认证。实验结果表明,基于JWT的认证方法及其安全策略能够有效解决身份和权限认证的问题。相较于传统的关系数据库存储用户权限,图数据库Neo4j和位图法能有效地提高权限认证效率。

Factors of Adherence to Concurrent Tuberculosis Treatment and Antiretroviral Therapy among HIV-TB Co-Infected Individuals in the East Region, Cameroon in the COVID-19 Era: A Retrospective Cohort Study

Context/Objectives: Tuberculosis (TB) and HIV co-infection is a serious health problem in Cameroon. The problems associated with poor adherence to treatment are on the increase worldwide. This problem can be observed in all situations where patients are required to administer their own medication, whatever the type of illness. The general objective of this study was to assess the factors affecting adherence to treatment among HIV-TB co-infected patients in health facilities in the East Region in the COVID context. Method: A retrospective cohort study before and during COVID-19 was conducted in HIV care units in 13 health districts in the East Region of Cameroon. Data were collected using a questionnaire recorded in the Kobo Collect android application, analyzed using SPSS version 25 software and plotted using Excel. Results: The pre-COVID-19 cohort compared to the during-COVID-19 cohort had a 1.90 risk of not adhering to treatment (OR: 1.90, CI {1.90 - 3.37}) and the difference was statistically significant at the 5% level (p-value = 0.029). Frequency of adherence was 65.4% (140/214). Adherence before COVID-19 was 56.9% whereas during COVID-19, it was 74.3%. Conclusion: The implementation of targeted interventions in the COVID-19 context, using evidence-based data and integrating the individual needs of HIV-TB co-infected patients, improved adherence to concurrent anti-tuberculosis treatment and antiretroviral therapy during the COVID-19 Era.

Development of D_α band symmetrical visible optical diagnostic for boundary reconstruction on EAST tokamak

To investigate the potential of utilizing visible spectral imaging for controlling the plasma boundary shape during stable operation of plasma in future tokamak, a D_α band symmetric visible light diagnostic system was designed and implemented on the Experimental Advanced Superconducting Tokamak(EAST). This system leverages two symmetric optics for joint plasma imaging. The optical system exhibits a spatial resolution less than 2 mm at the poloidal cross-section, distortion within the field of view below 10%, and relative illumination of 91%.The high-quality images obtained enable clear observation of both the plasma boundary position and the characteristics of components within the vacuum vessel. Following system calibration and coordinate transformation, the image coordinate boundary features are mapped to the tokamak coordinate system. Utilizing this system, the plasma boundary was reconstructed, and the resulting representation showed alignment with the EFIT(Equilibrium Fitting) results. This underscores the system's superior performance in boundary reconstruction applications and provides a diagnostic foundation for boundary shape control based on visible spectral imaging.

Spatial patterns of zooplankton abundance,biovolume,and size structure in response to environmental variables:a case study in the Yellow Sea and East China Sea

The Yellow Sea(YS)and East China Sea(ECS)are highly dynamic marginal seas of the northwestern Pacific Ocean.To gain an in-depth understanding of zooplankton community structure,zooplankton abundance,biovolume,and size structure in summer 2017 in the YS and ECS were assessed using ZooScan imaging analysis.Zooplankton abundance and biovolume ranged 2.94–1187.14 inds./m^(3)and 3.13–3438.51 mm^(3)/m^(3),respectively.Based on the biovolume data of the categorized size classes of 26 identified taxonomic groups,the zooplankton community was classified into five groups,and each group was coupled with distinctive oceanographic features.Under the influence of the Yellow Sea Cold Water Mass,the Yellow Sea offshore group featured the lowest bottom temperature(10.84±3.42℃)and the most abundant Calanoids(mainly in the 2–3 mm size class).In the Yellow Sea inshore group,Hydrozoans showed the largest biovolume and dominated in the 3–4-mm and>5-mm size classes.The East China Sea offshore group,which was affected by the Kuroshio Branch Current,featured high temperature and salinity,and the lowest bottom dissolved oxygen(2.58±0.5 mg/L).The lowest values of zooplankton abundance and biovolume in the East China Sea offshore group might be attributed to the bottom dissolved oxygen contents.The East China Sea inshore group,which was mainly influenced by the Zhejiang-Fujian Coastal Current and Changjiang Diluted Water,was characterized by high chlorophyll a and the largest biovolume of carnivorous Siphonophores(280.82±303.37 mm^(3)/m^(3)).The Changjiang River estuary offshore group showed the most abundant Cyclopoids,which might be associated with the less turbid water mass in this region.Seawater temperature was considered the most important factor in shaping the size compositions of Calanoids in different groups.

The Effects of Age and Ejaculatory Abstinence on Semen Quality and Reproductive Hormones in Africa and the Middle East

The aim of this study was to retrospectively evaluate the effects of male age and ejaculatory abstinence on semen parameters and reproductive hormones among men residing in Africa and the Middle East. A total of 70,142 semen analysis results were analysed and grouped according to the age intervals (16 - 20, 21 - 30, 31 - 40, 41 - 50, 51 - 60, >60) and ejaculatory abstinence (<2 days, 2 - 5 days and >5 days). Semen parameters i.e. volume, concentration, progressive motility, total progressively motile count, morphology, total normal sperm count, DNA fragmentation, viability, sORP, normed sORP were specifically evaluated. Additionally, for each age interval, reproductive hormones i.e. estradiol, luteinizing hormone, follicle stimulating hormone, testosterone and prolactin were evaluated. Semen volume, total progressively motile count, sperm morphology and total normal sperm count constantly decrease significantly after the age of 30 years. Sperm concentration started declining significantly after the age of 50 years. There was a constant age- related increase in number of spermatozoa with damaged DNA. sORP constantly increased up to 60 years. Furthermore, constantage-related decreases in FSH, serum testosterone and prolact in were observed from patients aged between 16 years and 60 years. Semen volume, sperm concentration, progressive motility and normal morphology were significantly higher in patients having > 5 days of abstinence. Patients having > 5 days of abstinence had the lowest normed sORP. Male age significantly affects sperm parameters and reproductive hormones in fertile and infertile men residing in Africa and the Middle East. Prolonged abstinence days provides better semen quality.

A fringe jump counting method for the phase measurement in the HCN laser interferometer on EAST and its FPGA-based implementation

Electron density in fusion plasma is usually diagnosed using laser-aided interferometers. The phase difference signal obtained after phase demodulation is wrapped, which is also called a fringe jump. A method has been developed to unwrap the phase difference signal in real time using FPGA, specifically designed to handle fringe jumps in the hydrogen cyanide(HCN) laser interferometer on the EAST superconducting tokamak. This method is designed for a phase demodulator using the fast Fourier transform(FFT) method at the front end. The method is better adapted for hardware implementation compared to complex mathematical analysis algorithms, such as field programmable gate array(FPGA). It has been applied to process the phase measurement results of the HCN laser interferometer on EAST in real time. Electron density results show good confidence in the fringe jump unwrapping method. Further possible application in other laser interferometers, such as the POlarimeter-INTerferometer(POINT)system on EAST tokamak is also discussed.

Persistent Variations in the East Asian Trough from March to April and the Possible Mechanism

The East Asian trough(EAT)profoundly influences the East Asian spring climate.In this study,the relationship of the EATs among the three spring months is investigated.Correlation analysis shows that the variation in March EAT is closely related to that of April EAT.Extended empirical orthogonal function(EEOF)analysis also confirms the co-variation of the March and April EATs.The positive/negative EEOF1 features the persistent strengthened/weakened EAT from March to April.Further investigation indicates that the variations in EEOF1 are related to a dipole sea surface temperature(SST)pattern over the North Atlantic and the SST anomaly over the tropical Indian Ocean.The dipole SST pattern over the North Atlantic,with one center east of Newfoundland Island and another east of Bermuda,could trigger a Rossby wave train to influence the EAT in March−April.The SST anomaly over the tropical Indian Ocean can change the Walker circulation and influence the atmospheric circulation over the tropical western Pacific,subsequently impacting the southern part of the EAT in March−April.Besides the SST factors,the Northeast Asian snow cover could change the regional thermal conditions and lead to persistent EAT anomalies from March to April.These three impact factors are generally independent of each other,jointly explaining large variations in the EAT EEOF1.Moreover,the signals of the three factors could be traced back to February,consequently providing a potential prediction source for the EAT variation in March and April.

EAST装置等离子体放电真空室真空泄漏研究

真空系统是EAST全超导托卡马克装置安全稳定运行的基础保障系统,真空泄漏会影响等离子体放电并对真空设备造成严重的损坏。随着EAST逐步地升级与改造,真空系统变得更加复杂,同时设备逐渐老化,导致泄漏的风险逐年增大。介绍了EAST内真空抽气系统、真空测量站及漏率实时监测系统。根据真空室压力变化数据,采用静态升压法分析了内真空室漏放率,计算出内真空室在等离子体放电前整体漏放率约为2.2×10^(-4)Pa·m^(3)/s。基于历年发生泄漏故障时的压力和残气成分数据,对EAST装置内真空室在不同运行阶段的不同类型泄漏进行了分析。研究发现,发生的泄漏位置不同、泄漏介质不同、器壁条件不同,在残气成分特征上表现差异较大。根据泄漏的特点,采取了不同的泄漏处理方式。研究结果可为及时准确地判断和处理EAST及未来聚变堆真空室的泄漏提供参考。

EAST-CTI测试平台上六硼化镧等离子体源的研制

为了更方便和深入研究紧凑环注入(CTI)系统产生的等离子体团在等离子体中的演化过程,特设计了一套大尺寸、均匀的六硼化镧等离子体源,用来产生磁化、高密度等离子体。等离子体源的阴极采用钨丝间接加热的方式来达到工作温度,阴极最高可达到1800℃。阳极采用耐高温、透过率50%的钼金属网,与阴极之间轴向间距1m。在阴极和阳极之间施加40~200V偏压,阴极发射的电子与中性气体碰撞、电离进而产生长1m直径100mm的稳态磁化等离子体柱。在台面实验中,测试了源的放电性能和等离子体相关参数。实验结果表明,在阴极发射电流密度为1~2A·cm^(-2)的情况下,测得的氩等离子体电子密度可达到10^(18)m^(-3)量级,电子温度约为8eV。通过增加阴、阳极之间偏压,阴极发射电流密度最高达到8.5A·cm^(-2),等离子体参数与托卡马克边界参数相近。该等离子体源满足设计要求并具备为EAST-CTI系统开展台面实验的能力。

Leading Pattern of Spring Drought Variability over East Asia and Associated Drivers

Drought events have become more frequent and intense over East Asia in recent decades,leading to huge socioeconomic impacts.Although the droughts have been studied extensively by cases or for individual regions,their leading variability and associated causes remain unclear.Based on the Standardized Precipitation Evapotranspiration Index(SPEI)and ERA5 reanalysis product from 1979 to 2020,this study evealuates the severity of spring droughts in East Asia and investigates their variations and associated drivers.The results indicate that North China and Mongolia have experienced remarkable trends toward dryness during spring in recent decades,while southwestern China has witnessed an opposite trend toward wetness.The first Empirical Orthogonal Function mode of SPEI variability reveals a similar seesawing pattern,with more severe dryness in northwestern China,Mongolia,North China,South Korea,and Japan but increased wetness in Southwestern China and southeast Asia.Further investigation reveals that the anomalously dry(wet)surface in North(Southwestern)China is significantly associated with anomalously high(low)temperature,less(more)precipitation,and reduced(increased)soil moisture during the previous winter and early spring,regulated by an anomalous anticyclone(cyclone)and thus reduced(increased)water vapor convergence.The spring dry-wet pattern in East Asia is also linked to cold sea surface temperature anomalies in the central-eastern Pacific.The findings of this study have important implications for improving the prediction of spring drought events in East Asia.

Forward modelling of the Cotton-Mouton effect polarimetry on EAST tokamak

Measurement of plasma electron density by far-infrared laser polarimetry has become a routine and indispensable tool in magnetic confinement fusion research.This article presents the design of a Cotton-Mouton polarimeter interferometer,which provides a reliable density measurement without fringe jumps.Cotton-Mouton effect on Experimental Advanced Superconducting Tokamak(EAST)is studied by Stokes equation with three parameters(s_(1),s_(2),s_(3)).It demonstrates that under the condition of a small Cotton-Mouton effect,parameter s_(2)contains information about Cotton-Mouton effect which is proportional to the line-integrated density.For a typical EAST plasma,the magnitude of Cotton-Mouton effects is less than 2πfor laser wavelength of 432μm.Refractive effect due to density gradient is calculated to be negligible.Time modulation of Stokes parameters(s_(2),s_(3))provides heterodyne measurement.Due to the instabilities arising from laser oscillation and beam refraction in plasmas,it is necessary for the system to be insensitive to variations in the amplitude of the detection signal.Furthermore,it is shown that non-equal amplitude of X-mode and O-mode within a certain range only affects the DC offset of Stokes parameters(s_(2),s_(3))but does not greatly influence the phase measurements of Cotton-Mouton effects.

The Impacts and Causes of Land Fragmentation on Farm Productivity: Case Review of East African Countries

This report provides an overall assessment of land fragmentation problems in East Africa. Many parts of East Africa have become highly fragmented, putting development systems and activities in these areas at risk of complete collapse. Land fragmentation occurs when land gets converted for agriculture, industrialization, or urbanization, invaded by non-local plants, or enclosed for individual use and by subdividing farmlands into subsequent smaller units called parcels with varying average farm sizes. Fragmentation results from inappropriate agricultural development processes and ineffective land use planning that fails to recognize how farmland is used, and the importance of its interconnected areas. Insecurity of tenure and resource rights are key factors in making this possible. Land fragmentation is one of the key reasons why the ability of most resources in East Africa becomes scarcer, and those remaining become “privatized” by more powerful community members—keen to maintain their access to them. Such individualistic attitudes are new and disadvantage the poorest even further by affecting the traditional customary safety nets and agricultural outputs. Neither the government nor customary governance systems effectively protect resource access for the poorest. This review summary report identifies the key causes, measures, and implications, government interventions, and the common remedies to land fragmentation problems in the East African Countries of Kenya, Uganda, Rwanda, and Tanzania including neighboring Ethiopia, and the Sudan. The findings indicated from 2005 to 2015, the population kept increasing for all the named countries in East Africa with Rwanda and Uganda having a substantial increase in population density. The study review further explores the trend in the performance of agriculture by average farm sizes within the intervals of five years by highlighting their strong linkages and found that the average farm size has declined drastically, especially for Kenya. This can only mean that small farms kept becoming smaller and smaller and that there were more small-scale farmers. The results further depicted that the major and commonly cultivated food crops among the East African countries include maize, sorghum, rice, cassava, sweet potatoes, bananas, Irish potatoes, beans, peas, etc., with maize yields (Mt/ha) in 2003 for Uganda being the highest (1.79 Mt/ha) and the lowest in Rwanda (0.77 Mt/ha) respectively. Therefore, from the review results, recommendations are being made as to how the negative impacts of land fragmentation on agricultural productivity can be reduced or mitigated. One way is by community sensitization and awareness about the importance of land consolidation and its proposition on farm productivity.

Development of a 2D spatial displacement estimation method for turbulence velocimetry of the gas puff imaging system on EAST

A gas puff imaging(GPI)diagnostic has been developed and operated on EAST since 2012,and the time-delay estimation(TDE)method is used to derive the propagation velocity of fluctuations from the two-dimensional GPI data.However,with the TDE method it is difficult to analyze the data with fast transient events,such as edge-localized mode(ELM).Consequently,a method called the spatial displacement estimation(SDE)algorithm is developed to estimate the turbulence velocity with high temporal resolution.Based on the SDE algorithm,we make some improvements,including an adaptive median filter and super-resolution technology.After the development of the algorithm,a straight-line movement and a curved-line movement are used to test the accuracy of the algorithm,and the calculated speed agrees well with preset speed.This SDE algorithm is applied to the EAST GPI data analysis,and the derived propagation velocity of turbulence is consistent with that from the TDE method,but with much higher temporal resolution.