Abstract The technique of indirect-drive cryogenic pure deuterium layered implosion is unique among published works in the research of inertial confinement fusion. After its feasibility was demonstrated recently, we proceeded to improve the implosion performance by using a 2-shock shaped pulse. The target design was evolved from an ignition target design with modifications compatible with current energy scale. The radiation uniformity was confirmed by the dual-axis keyhole targets and cryogenic gas-filled targets. The adiabat of the fuel was controlled by tuning shocks to emerge at the ice-gas interface. The implosion performance of the layered targets were then investigated. The pure deuterium layers of good quality were maintained for a few minutes. The lasers were fired during the survival time of such layer quality. The resulting neutron yield was 9.6×1010, and the hotspot pressure was 30Gbar. Radiative hydrodynamic simulations were carried out using as-shot target and laser parameters, and compared with the experimental measurements. The yield of clean was about 19%. The residual radiation non-uniformity alone cannot explain the observed performance degradation. The hydrodynamic instabilities seeded by ice roughness should play a role in decreasing the hotspot clean volume.

A cryogenic target filled with a solid-liquid mixed deuterium layer is proposed to resolve the defects in solid monocrystalline deuterium and to serve as a primary substitute for deuterium-tritium cryogenic targets to accelerate the iteration and optimization of physical designs in inertial confinement fusion (ICF) experiments. However, fabricating and maintaining such a uniform deuterium shell until shot presents major challenges, such as achieving sufficiently rapid cooling during crystallization, ensuring fast solid deuterium migration from capsule poles to the equator during maintenance, and minimizing perturbation during cryogenic target system shroud removal immediately before the shot. These challenges are addressed by a novel thermal-mechanical package design, optimizing the arm-sleeve joint and laser entrance hole transmissivity, as well as the thermal shield structures and thermal loads. The designs and improvements are analyzed numerically and verified experimentally to guide the production of viable uniform mixed-phase shells for shot delivery.

The roughness of the fuel ice layer at low modes significantly impacts the hydrodynamic instability in inertial confinement fusion experiments with indirect-drive cryogenic targets. It is primarily determined by the thermal uniformity of the capsule. Due to the β-decay heat of tritium, the temperature profiles of targets filled with deuterium-tritium differ from those filled with deuterium-deuterium in a cylindrical hohlraum. The cylindrical shape causes the equator of the capsule to be cooler than the two poles in the steady state without any intervention. Tuning the vertical temperature distribution is essential and requires a high thermal resistance in the target thermal mechanical package. It is very difficult for a compact target which is just half of the National Ignition Facility (NIF) target scale, and is contrary to the previous design of deuterium- deuterium target, which used a high-conductive jacket made from Oxygen-Free Copper (OFC), to provide a relatively uniform thermal field around the capsule. To realize the vertical tuning capability and achieving global thermal uniformity of the capsule, we propose in this paper a novel design featuring a grooved aluminum-alloy jacket, as well as the methods to improve thermal contact reliability and conductivity, including decreasing the width of arm-jacket interface, enhancing the adhesive conductivity by doping silver, and replacing the aluminum diagnosis band with conductive OFC. We further verified this design through experiments. It has reduced the global temperature difference of the capsule by about 70 % and significantly improved the quality of the deuterium-tritium ice layer.

To achieve ignition in a laboratory via inertial confinement fusion, a spherical capsule containing a frozen layer of deuterium and tritium (DT) fuel will be imploded on an MJ-class laser facility. However, if pure deuterium fuel can be used in place of DT fuel for tuning shots, we may speed up the process of ignition experiments while maintaining the surrogacy by significantly reducing the level of radioactivity. Unfortunately, it has long been assumed that neither the approach of symmetrical infrared irradiation used in the Omega direct-drive experiments nor the method of beta-layering used in the NIF experiments can be used to smooth the D layered capsule in cylindrical hohlraums. The difficulty in smoothing the D ice layer prevents us from taking advantage of cryogenic D-layered capsules in indirect-drive experiments. In this work, we established a procedure to form a uniform D-ice layer for capsules held in cylindrical hohlraums and carried out indirect-drive cryogenic D-layered implosion experiments using a squared laser pulse on the Shenguang Laser Facility in China. The quality of the D ice layer is characterized by phase-contrast imaging. The root-mean-square of the power spectrum in modes 2–100 is about 2.2 μ m. The implosion performance of the D-layered capsules is close to the prediction of one-dimensional simulations. The measured neutron yield and areal fuel density are 1.2 × 10 11 and 80 mg cm −2 , respectively.

基于排放因子法构建了包含种植业和牲畜养殖业的农业系统温室气体排放核算体系,系统核算了1980—2020年我国全国尺度上的农业系统温室气体排放总量和变化趋势,并在区县级尺度下对1980、2000、2011年的中国农业系统的温室气体排放量进行核算,对比不同阶段农业系统温室气体排放变化的时空异质性规律.研究发现:1980—2020年我国农业系统温室气体排放量呈波动增长趋势,增长了近46％.CH4是农业系统排放贡献最大的温室气体,占总排放量的47.33％.我国农业系统温室气体排放与不同地区农业生产方式有关,CH4排放量高的地区主要位于我国主要水稻产区以及旱地作物产区.CO2排放量高的地区主要位于东北、西北等地区以及华东地区.N2 O排放量较高地区主要位于西北的主要畜牧养殖地区,以及我国农业经济发展水平高的中南部地区.研究有助于揭示我国农业温室气体排放的动态特征,现状规律,以及空间差异性特征,从农业减排角度为实现双碳目标提供科学参考.

北海公园冰上运动是北京传统体育文化遗产的重要组成内容以及冬季休闲旅游的代表性符号,强化其气候变化影响与适应研究,对于应对全球变化的挑战、践行"大力发展冰雪经济"的指示具有重要意义.本文从多源文献中提取分析了其冰场多年启闭日期(间接指示冰层厚15 em)的变化特征,并结合气温器测数据以及4种气候情景数据(SSP1-2.6、SSP2-4.5、SSP3-7.0和SSP5-8.5),利用留一交叉验证法探讨了不同温度指标和拟合方程的预测效果差异,进而对未来冰上运动季的变化、潜在影响与适应对策进行分析.结果 表明:①1989-2018年冰上运动季始日、末日和持续长度的均值分别为1月1日、2月5日和36d,对应的趋势表现为不显著的推迟(1.00d/10a)、提前(-0.77d/10a)和延长(1.11d/10a),时序变化可区分为1989-2000年、2001-2013年和2014-2018年3个阶段.②冰上运动季始、末日分别对其日期前59 d的日最低温和前94 d的日最高温有较好响应,利用这两个指标和玻尔兹曼函数可更好预测冰上运动季变化.③2021-2099年冰上运动季始日、末日和持续长度的均值分别较1989-2018年晚1d、早1d和缩短2d,3个指标变幅一致缩小,对应的0.14d/10a、-0.21d/10a和-0.34d/10a的趋势均达到0.01的显著性水平.④未来79 a内冬季两大节庆中元旦冰上运动的适宜性要大于春节,其中春节的适宜性在4种气候情景下相差不大,而元旦的适宜性则在4种情景下有一定差别.⑤在相关预估结果上,BCC-CSM2-MR、CanESM-5和UKESM这3种区域气候模式并没有太大差异,而热岛效应影响尚待深入研究.⑥为了在气候变暖背景下促进体旅融合消费、保障冰上运动产业高质量发展,运营企业应采取强化游客安全保障、扩展旅游产品谱系、购买冰量保险等全方位主动适应措施,研究者应加强研究气候变化影响的复杂性、改进旅游流的预测效果,而管理部门应大力推动产业风险管理报告的编制,充分重视气候变化风险的动态评估.

立足区域土壤硒资源优势、发展富硒农业特色经济,是提高农业经济效益和振兴乡村产业的一条有效途径.借助空间自相关、聚类分析和适宜性评价等方法,探究研究区表层土壤各理化性质富集特征;以生态位理论为指导,以区域土壤硒资源状况和富硒农业发展要求为基础,结合自身土壤条件和生态敏感性特点,构建了土壤硒资源开发利用生态位适宜性评价指标体系.结果表明:研究区表层土壤硒含量介于0.09～0.41mg·kg-1之间,全局莫兰指数均值为0.848(P<0.01),存在强烈的空间正相关性,有机质含量介于2.84～39.60g·kg-1之间,土壤pH值介于7.65～8.89之间,整体偏碱性.结合农用地土地利用等别等方面,根据生态位适宜性评价结果将研究区分为富硒产业发展区、重点农业生产区和综合产业发展区3种类型,并提出相应的发展措施,为实现土壤硒资源合理利用和富硒农业科学发展提供参考.

In indirect-drive inertial confinement fusion, thin films on laser entrance hole (LEH) windows are needed to reflect thermal infrared radiation (IR) and to protect the deuterium-tritium (D-T) cryogenic shell. In this paper, a set of ultrathin aluminum films deposited on freestanding polyimide as LEH windows were studied on optical properties in the IR band. The influences of thickness and gas pressure on the IR transmittivity of these films were examined. It was found that gas pressure plays an important role in the IR transmission and microstructure changes of LEH films because of elastic modulus mismatch between aluminum and polymide. It is undoubted that the aluminum/polymide film can block thermal IR and protect the D-T cryogenic shell when gas pressure is less than 20 KPa.

Axial resolution improvement in the low coherence interferometry (LCI) with a three-zone annular phase filter is demonstrated. The sidelobes resulting from the super-resolving features of the phase filter can be suppressed by the coherence gate of the LCI. The parameters of the filter are optimized to increase the axial gain.. A as large as possible while maintaining an acceptable value of the Strehl ratio S and the transverse gain.. T through the numerical simulations. The effect of the actual broadband spectrum and Gaussian amplitude profile of the incident light on the performance of the designed filter is investigated. With the designed filter, the experimental axial gain is 1.25 while the intensity loss is about 5.5 dB with the mirror sample, which is also verified with the dimensional measurements of a transparent inertial confinement fusion (ICF) shell.

In inertial confinement fusion experiments, fuel quality is determined mainly by the thermal environment of the capsule in the layering procedure. Owing to the absence of a radial thermal gradient, formed deuterium–deuterium (DD) ice shells in the capsule are thermally instable. To obtain a solid DD layer with good quality and long lifetime, stringent demands must be placed on the thermal performance of cryogenic targets. In DD cryogenic target preparation, two issues arise, even after the capsule’s temperature uniformity has been improved by the use of thick aluminized films. The first is the inconsistent ice shape, which is related to the capsule’s thermal field. In this article, some typical fabrication details are investigated, including adhesive penetration during assembly, the presence of the fill tube, the optical properties of the hohlraum and film surfaces, the jacket–hohlraum connection, deviations in capsule location, and asymmetrical contact at the arm–jacket interfaces. Detailed comparisons of the thermal effects of these factors provide guidance for target optimization. The second issue is the instability of seeding crystals in the fill tube due to unsteadiness of the direction of the thermal gradient in the fill tube assembly. An additional thermal controller is proposed, analyzed, and optimized to provide robust controllability of tube temperature. The analysis results and optimization methods presented in this article should not only help in dealing with thermal issues associated with DD cryogenic targets, but also provide important references for engineering design of other cryogenic targets.

Cryogenic target is one of the key components of inertial confinement fusion. The removal degree and efficiency of impurity gas in cryogenic target are of great significance to the on-line preparation of ice layer for cryogenic target fuel. According to the design requirements of cryogenic target physics for impurity content in ice layer, the influence factors of upper limit of partial pressure are analyzed, based on the derivation of the calculation formula of maximum allowable partial pressure of impurity gas in the target. Then the flow field of air and hydrogen in microchannels is investigated, and the filling and evacuation model of gas flow in a microscaled filling tube is established. The dynamic simulations of microtubules with different lengths and diameters are carried out. The results show that the microtubules with a length of 5 mm could save 80% of the time compared with the microtubules of 50 mm in length when the microtubule is 5 μm in diameter. At the same time, the total flow washing time decreases by 46% when the diameter of 2 μm is doubled under the condition of 20-mm-long microtubule. Considering the requirements for efficiency and fusion stability, four kinds of tubes are proposed and simulated. The results indicate that the conical transition tube has a strong flow capacity and high flow evacuation efficiency, and is suitable for use as a filling microtubule. On the basis of the best tube shape, the comparison between the two processes under different intermediate pressures is carried out with the time and number of filling and evacuating serving as evaluation criterion. Ultimately, the intermediate pressure of 52000 Pa is selected, the total number of evacuation is 10 and the time is 758 s. Finally, the effect of temperature on the evacuation efficiency is studied in a temperature range of 113 K－293 K in steps of 60 K. The results show that the total time of filling and evacuation will be reduced by 15% on the basis of normal temperature when the temperature is reduced by 60 K, which proves the feasibility of evacuation at low temperature in practical operation.

A cylindrical cryogenic target containing deuterium fuel acts as an important surrogate to help understand implosion physics before the deuterium-tritium capability is brought online. Uniformity of the deuterium ice thickness is a key parameter for the inertial confinement fusion (ICF) experiments. Achieving and retaining a uniform deuterium ice layer in capsule without infrared radiation is difficult in engineering. The method used to calculate the ice thickness deviation of deuterium–tritium fuel is invalid when the bulk heat generation is equal to zero. Appearance solutions of the deuterium ice in steady state conclude that a uniform ice layer cannot be retained for long without infrared radiation. A transient algorithm by integrating heat transfer theory, the equation derived from Stefan problem and mass conservation with moving mesh technics in a finite element model can be applied to predict deuterium ice spherical symmetry degeneration. It is certified with good reliability by comparing the simulated results with theoretical and experimental data. As for the deuterium targets, the characteristics of linear approximation and integrability avert heavy work of moving mesh in analyses of stable and unstable scenarios. The work has great support for the cryogenic processing and engineering design of ICF targets.

The high degree of control afforded by microfluidic techniques enables the generation of monodisperse water-in-oil-in-water (W1-O-W2) double droplets, which are transformed to solid-shelled capsules through solvent-evaporation-based microencapsulation. Experimental investigations and numerical simulations are combined to explore the developments for controlled fabrication of solid-shelled capsules with designed geometry sphericity. The designed geometry sphericity arises from the competition between solidification and shear stress generated by the shear flow field. An increasing viscosity of continuous phase resists the solidification, which contributes to improve the sphericity of the solid-shelled capsules, but intensifies the shear stress of the flow filed, which promotes the deformation of the droplets. Therefore, the continuous phase viscosity exerts a parabolic effect on the deformation of double droplets and the sphericity of the resulting capsules. Accordingly, spherical and non-spherical such as oval and ellipsoid jujube core like solid-shelled capsules can be obtained by controlling the viscosity of the shear flow field.

W1-O-W2 composite droplets are prepared using droplet microfluidics and core-hollow poly(α-methylstyrene) (PAMS) shells are fabricated by microencapsulation. This work examines the effects of alkanes on stability and deformation of double droplets. Results manifest that alkanes benefit resisting the deformation of the double droplets and improving the sphericity of the resulting polymer shells. Moreover, with shortening the chain length of the alkane, the deformation of double droplets is resisted and the sphericity of the solidified shells is improved. However, the addition of alkanes promotes the coalescence between the droplets, decreasing the yield of individual shells. The results presented in this work provide a feasible method to fabricate individual polymer shells with high sphericity.

The present work applies the finite element method to calculate the maximum allowable time that cryogenic inertial confinement fusion (ICF) targets can be exposed to infrared radiation (IR). Hence, a 3-D numerical model integrated with discrete coordinate radiation model was developed to investigate the influence of transmittance of the laser entrance holes (LEHs) and boundary conditions on the temperature field distribution and the maximum DT layer deterioration time for CH, Be, and diamond capsules. Our study shows that introducing such a radiation model can accurately obtain more detailed spatial and temporal distribution information in the ICF targets. The simulation results demonstrate that the Be and diamond capsules provided much better temperature field homogenization than the CH capsule under equivalent boundary conditions, but the CH capsule was heated more by IR radiation than the Be and diamond. In addition, the maximum DT layer deterioration time was significantly increased to 3 s when decreasing the transmittance of the LEH from 0.2 to 0.01. However, either reducing the capsule IR absorption or increasing the inner hohlraum IR absorption demonstrated no conclusive increase in the maximum DT layer deterioration time. These results are expected to provide useful parameters in the design of cryogenic targets and shroud systems.

特色小镇与田园综合体是当前乡村发展代表创新突破的思维模式,如何建设好、发展好美丽乡村、特色小镇、田园综合体,实现两者的联动创新发展涉及到顶层设计、产业生态圈构建、重大项目建设、投融资模式创新与运营等多行业、多要素的系统集成.

Polymer shells prepared by the microencapsulation technique with perfect sphericity and defect-free surface finish are demanded in inertial confinement fusion (ICF) experiments. The sphericity and surface finish are some of the hardest specifications to fulfill. Driven by the need to improve qualities of the polymer shells to meet the critical specifications, the effects of fluorobenzene (FB) mass transfer rate on sphericity and surface finish were investigated and the mechanisms of the effects of FB mass transfer on sphericity and surface finish of poly-α-methylstyrene (PAMS) were also discussed. The sphericity and surface finish of the PAMS shells are greatly improved by decreasing the FB mass transfer rate. The calculative frequency of the final shells with an out-of-round (δ OOR) of less than 2 μm increases from 30% to 80%, while the power spectra density (PSD) plot gets closer to the specification of the national ignition facility (NIF). The tracking experiments show that the curing process is extended and the percolation transition is also postponed by decreasing the FB mass transfer rate. Therefore, the interfacial tension can work sufficiently, helping make double droplets become spherical, since the double droplets' stay in the liquid state is effectively extended. Moreover, the Marangoni instabilities at the O-W2 boundary are also restrained by controlling the mass transfer, due to the diffusivity of FB being slowed down. Both the results and methods presented in this work provide a more in-depth understanding of the curing process and the mass transfer, to the benefit of fabricating polymer shells with high sphericity and defect-free surface finish used in ICF experiments.

Millimeter-scale polymer shells with stringent specifications such as sphericity, wall thickness uniformity and surface finish are needed in inertial confinement fusion (ICF) experiment. In order to meet these stringent specifications, n-hexadecane (n-HD) is introduced in oil phase to improve the sphericity of poly-α-methylstyrene (PAMS) shells. The results show that n-HD decreases the survival rate of the final PAMS shells, since coalescence between W1/O/W2 double droplets occurs owing to phase separation during the curing process. However, characterization results show that the addition of n-HD into O phase leads an increasing interfacial tension at O-W2 interface, which is considered as the only driving force for sphericity. Tracking experiment data indicates that the addition of n-HD can effectively extend the curing process. A percolation threshold is determined at about 58% where PAMS large-scale networking occurs and over where the deformation of the droplets is considered irreversible. So the addition of n-HD can extend the period W1/O/W2 droplets stay in liquid with nice fluidity, where the interfacial tension can work sufficiently and thus improving the final sphericity of polymer shells. Furthermore, when the mass fraction of n-HD is larger than 2.0%, porous PAMS shells can be obtained.

Due to the high spatial resolution and contrast, the optical lens coupled X-ray in-line phase contrast imaging system with the secondary optical magnification is more suitable for the characterization of the low Z materials. The influence of the source to object distance and the object to scintillator distance on the image resolution and contrast is studied experimentally. A phase correlation algorithm is used for the image mosaic of a serial of X-ray phase contrast images acquired with high resolution, the resulting resolution is less than 1.0 μm, and the whole field of view is larger than 1.4 mm. Finally, the geometric morphology and the inner structure of various weakly absorbing samples and the evaporation of water in the plastic micro-shell are in situ characterized by the optical lens coupled X-ray in-line phase contrast imaging system.

All planned inertial confinement fusion (ICF) capsule targets except machined beryllium require plastic mandrels with tight requirements on which the ablator is built. In this paper, the fabrication of poly(-methylstyrene) (PAMS) mandrel is studied. PAMS mandrels are produced by using microencapsulation technique. This technique involves producing a water droplet (W1) encapsulated by a flourobenzen (FB) solution of PAMS (O) with a droplet generator, and this droplet is then flushed off by external phase (W2), forming a water-in-oil-in-water (W1/O/W2) compound-emulsion droplet, which is suspended in a stirred flask filled with external phase to cure. The encapsulation process is based on a microfluid technique, which can achieve the controlled production of millimeter-scale PAMS mandrels. In this work, capillaries-based co-flowing microfluidic triple orifice generator is designed and built to fabricate W1/O/W2 droplets. Two configurations of the droplet generator:one-step device and two-step device, are employed in this experiment. In one-step device, the end of oil phase capillary is located at the same position as the end of inner water phase capillary. So the core droplet and the shell droplet break off from their capillaries ends at the same time, forming a W1/O/W2 droplet. While in the two-step device, the W1 phase capillary tip is located upstream to the W2 phase capillary tip. As a result, the core droplet and the shell droplet depart from the ends of their capillaries respectively, forming a W1/O/W2 droplet as well. Differently, the shell droplet contains only one core droplet in one-step generator, while several core droplets are contained in the shell droplet in two-step generator. In this paper, the mechanism of the droplet formation and the effect of the flow rate on the size of the droplet are studied with these two configurations. Results show that tiny difference between the two generators will lead to great differences in droplet formation mechanism and size control. In the two-step generator, the inner phase flow rate has little influence in the outer diameter of the compound-emulsion droplet. The diameters of the compound-emulsion droplets have a similar change to the diameters of the single droplets (O/W2). In one-step device, the inner phase flow rate has a significant influence on the outer diameter of the double-emulsion droplet because of the existence of W1-O interface. Finally, the compound-emulsion droplets fabricated in this experiment are cured in external phase, after which PAMS mandrels are fabricated. The diameters of the final PAMS mandrels are measured with optical microscope. The distribution of the diameters well concentrates in an area of (200010) upm, which is favorable for producing the PAMS mandrels with a diameter of 2000 upm.