Compact intense electron-beam accelerators based on high energy density liquid pulse forming lines

This paper provides a review of the compact intense electron-beam accelerators (IEBAs) based on liquid pulse forming lines (PFLs) that havebeen developed at the National University of Defense Technology (NUDT) in China. The history and roadmap of the compact IEBAs used todrive high-power microwave (HPM) devices at NUDT are reviewed. The properties of both de-ionized water and glycerin as energy storagemedia are presented. Research into the breakdown properties of liquid dielectrics and the desire to maximize energy storage have resulted in theinvention of several coaxial PFLs with different electromagnetic structures, which are detailed in this paper. These high energy density liquidPFLs have been used to increase the performance of IEBA subsystems, based on which the SPARK (Single Pulse Accelerator with spark gaps)and HEART (High Energy-density Accelerator with Repetitive Transformer) series of IEBAs were constructed. This paper also discusses howthese compact IEBAs have been used to drive typical HPM devices and concludes by summarizing the associated achievements and theconclusions that can be drawn from the results.

Electron Acceleration in the Cone-shaped Extra-intense Stationary Laser Field

A technique of electron acceleration in the cone shaped stationary laser field is proposed. An electron acceleration in this laser is studied, which shows that there is no electron bunching but there exists electron capture in this laser field.

Acceleration of Protons from a Double-Layer or Multi-Ion-Mixed Foil Irradiated by Ultraintense Lasers

Acceleration of protons by the radiation pressure of a circularly polarized laser pulse with the intensity up to 1021 W/cm^2 from a double-layer or multi-ion-mixed thin foil is investigated by two-dimensional particle-in-cell simulations. The double-layer foil is composed of a heavy ion layer and a proton layer. It is found that the radiation pressure acceleration can be classified into three regimes according to the laser intensity due to the different critical intensities for laser transparency with different ion species. When the laser intensity is moderately high, the laser pushes the electrons neither so slowly nor so quickly that the protons can catch up with the electrons, while the heavy ions cannot. Therefore, the protons can be accelerated efficiently. The proton beam generated from the double-layer foil is of better quality and higher energy than that from a pure proton foil with the same areal electron density. When the laser intensity is relatively low, both the protons and heavy ions are accelerated together, which is not favorable to the proton acceleration. When the laser intensity is relatively high, neither the heavy ions nor the protons can be accelerated efficiently due to the laser transparency through the target.

Simulation of high-intense beam transport in electrostatic accelerating column

An electrostatic accelerating column was designed and fabricated by Lanzhou University for an intense DT/D-D neutron generator. In order to achieve a neutron yield of 5.0 × 10^(12)n/s, a deuteron beam of 30 mA,accelerated to 400 kV, and transported in the electrostatic accelerating column smoothly are required. One particle-in-cell code BEAMPATH was used to simulate the beam transport, and the IONB 1.0 code was used to simulate the intense beam envelopes. Emittance growths due to space charge effect and spherical aberration were analyzed. The simulation results show that the accelerating column can transport deuteron beam of 30 mA smoothly and the requirement for the neutron generator is satisfied.

Dielectric Laser Accelerators Driven by Ultrashort, Ultraintense Long-Wave Infrared Lasers

Particle acceleration driven by intense lasers has long been a frontier of research in the field of laser engineering physics due to its extremely high acceleration gradient.Recently,dielectric laser accelerators(DLAs)have become a new research hotspot due to their ability to achieve gigavolt-per-meter acceleration gradients on compact chip-level all-optical structures.In comparison to the currently widely used solid-state laser with a 1-μm wavelength,long-wave infrared(LWIR)lasers with a length of about 10μm offer several unique advantages,including the ability to obtain a large electric charge of particle beams and lower energy divergence.These advantages have been validated in plasma-based laser accelerators as well as DLAs.Although the system is still in its early stages of development,the use of LWIR lasers for driving DLAs has special significance,including but not limited to easier processing of optical chips and larger acceleration channels.This review will provide a detailed introduction to this field from 2 aspects:DLAs and ultrashort and ultraintense LWIR lasers based on CO_(2) laser amplifiers.

Relationship between Modified Mercalli Intensity and peak ground acceleration in Myanmar

In this study, the previously reported isoseismal maps are compiled and used to carefully investigate the macroseismic intensity in terms of the Modified Mercalli Intensity (MMI) scale, based on the engineering ground-motion parameter, as the peak ground acceleration (PGA), inferred from the ground-motion attenuation characteristic of Myanmar. The preliminary relationship between the MMI and PGA is reported to be a function of log10(PGA) = 0.2526MMI – 3.1006. The strongly correlated MMI-PGA relationship obtained in this study, if confirmed, will be particularly useful in real-time applications for damage prediction or engineering parameter determination when an earthquake occurs in or nearby to Myanmar. Compared with the previously proposed MMI-PGA relationships for other regions, the standard of building construction in Myanmar is not high enough to withstand the hazards from earthquakes, particularly at higher levels of ground motion. Therefore, the standard building code for Myanmar should be modified in order to reduce future hazards arising from earthquakes.

Absorption of ultrashort intense lasers in laser–solid interactions

With the advent of ultrashort high intensity laser pulses, laser absorption during the laser–solid interactions has received significant attention over the last two decades since it is related to a variety of applications of high intensity lasers,including the hot electron production for fast ignition of fusion targets, table-top bright X-ray and gamma-ray sources,ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Normally, some absorption mechanisms found for nanosecond long laser pulses also appear for ultrashort laser pulses. The peculiar aspects with ultrashort laser pulses are that their absorption depends significantly on the preplasma condition and the initial target structures. Meanwhile, relativistic nonlinearity and ponderomotive force associated with the laser pulses lead to new mechanisms or phenomena, which are usually not found with nanosecond long pulses. In this paper, we present an overview of the recent progress on the major absorption mechanisms in intense laser–solid interactions, where emphasis is paid to our related theory and simulation studies.

高功率环境下多丝靶设计及运行考虑

多丝靶被广泛用于束流截面测量,但是常常因为束流功率沉积导致丝被损坏。为了研究不同束流参数以及丝靶设计与丝上温度和丝变形之间的关联,开发了基于后向欧拉法的自适应步长多丝靶温度数值模拟程序,并在离子源平台上开展了由温度导致的多丝靶变形实验。模拟和实验表明:在缺失恒定张力的情况下,温度是导致丝变形的主因。基于我们的模拟计算、实验验证以及操作经验,在丝温度低于1 300 K的情况下,拉丝采用锡焊固定的方式,其结构简单成本低;在高于1 300 K的情况下,采用弹簧张力的固定方式,可以提供恒定的张力,避免丝变形。

区域水资源集约安全利用评价:以北京市为例

构建了区域水资源集约安全利用评价模型,对北京市2008−2019年的水资源集约安全利用进行评价.结果显示:北京市水资源集约安全利用情况在2010年达到最佳状态,2012年最差,但近年来逐渐向好发展;水资源集约利用指数除2013年有所下降,整体上呈逐年上升趋势;水资源安全利用指数变幅较大,其中2010年最佳,2012年最差,2013年后也在逐年向好发展.北京市在推进节水型社会建设的同时,也应筑牢生态安全屏障:在改善水资源集约利用方面,需紧抓节水工作,提高水资源利用效率,同时也要加快调整发展模式,优化产业布局;在改善水资源安全利用方面,应严格控制污染物排放总量,大力推进城市污水处理与资源化.

Xe^(23+)离子束轰击低温工况下的无氧铜表面解吸性能研究

强流重离子加速器运行时产生动态真空效应引起束流寿命缩短,需安装无氧铜束流准直器来降低该效应。为探究无氧铜材料在离子束轰击下的解吸性能,本工作设计并研制了满足低温工况的解吸率测试装置,在兰州重离子加速器国家实验室利用Xe^(23+)离子束完成了无氧铜温度在4.2 K、20 K、77 K和300 K,以及束流能量为0.58 MeV/u、0.96 MeV/u和1.3 MeV/u的在束试验。结果表明,离子束轰击无氧铜表面时解吸出最多的分子为H_(2),其次分别为H2O、CO、CO_(2)、Ar和O_(2);当温度为4.2 K、束流能量为0.58 MeV/u时无氧铜解吸出H2的比例为87.74%。在同一能量下,随着无氧铜表面温度的升高,解吸率呈增加趋势,能量为0.58 MeV/u时,4.2 K下无氧铜的解吸率仅为25 mol/ion,小于300 K时的600 mol/ion,表明温度越高其解吸产额越大。在同一温度下,随着束流能量的升高无氧铜表面解吸率增加,但增加趋势逐渐减缓,解吸产额趋向饱和。

Wave Intensity的命名探讨

目的探讨Wave Intensity的中文命名,期望加快该项新技术的临床推广应用。方法查阅文献,结合临床应用体会,通过与传统波强概念对比、时相分析、与加、减速度的关系以及根据检测方法不同命名。结果从不同的研究角度得到不同的命名。结论建议将WI命名为"瞬时波强",简称WI;将W1命名为"瞬时加速度波强",简称W1;将W2命名为"瞬时减速度波强",简称W2,供研究时参考。

基于等损伤的主余震序列型地震动PGA放大系数谱研究

大地震发生后往往会伴随强余震发生,强烈余震会加重结构的破坏程度,在抗震设计及结构损伤评估中考虑余震的影响是一重要课题。采用NGA-West2数据库建立主余震序列型地震动记录数据集,基于损伤等效思想定义主余震作用下PGA放大系数α,针对单自由度体系结构,通过动力时程分析建立不同相对强度、不同场地条件下平均PGA放大系数谱,进一步通过回归分析构建PGA放大系数谱的预测方程,分析统计结果的离散性。结果表明:PGA放大系数谱受场地条件影响较小,受主余震相对强度影响显著;放大系数谱值随周期增大而减小。谱预测方程能够提供目标损伤下结构的主震PGA放大需求,并可以作为设计谱调整系数使用,以实现在结构抗震设计及结构损伤评估中考虑余震的影响。

Detailed seismic zoning of the East Kazakhstan region in the Republic of Kazakhstan

Kazakhstan is currently drafting new construction regulations that comply with the major provisions of the Eurocodes.Such regulations are created on the basis of seismic zoning maps of various degrees of detail,developed by our Institute of Seismology using a new methodological approach for Kazakhstan.The article is about creating the first normative map of the Detailed Seismic Zoning on a probabilistic foundation for the Republic of Kazakhstan’s East Kazakhstan region.We carried out the probabilistic assessment of seismic hazard using a methodology consistent with the main provisions of Eurocode 8and updated compared with that used in developing maps of Kazakhstan’s General Seismic Zoning and seismic microzoning of Almaty.The most thorough and current data accessible for the area under consideration were combined with contemporary analytical techniques.Updates have been done to not only the databases being used but also the way seismic sources were shown,including active faults now.On a scale of 1:1000000,precise seismic zoning maps of the East Kazakhstan region were created for two probabilities of exceedance:10%and 2%in 50 years in terms of peak ground accelerations and macroseismic intensities.The obtained seismic hazard distribution is generally consistent with the General Seismic Zoning of Kazakhstan’s previous findings.However,because active faults were included and a thoroughly revised catalog was used,there are more pronounced zones of increased danger along the fault in the western part of the region.In the west of the territory,acceleration values also increased due to a more accurate consideration of seismotectonic conditions.Zoning maps are the basis for developing new state building regulations of the Republic of Kazakhstan.

Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities

Laser-driven ion sources are a rapidly developing technology producing high energy,high peak current beams.Their suitability for applications,such as compact medical accelerators,motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers.These applications not only require high beam energy,but also place demanding requirements on the source stability and controllability.This can be seriously affected by the laser temporal contrast,precluding the replication of ion acceleration performance on independent laser systems with otherwise similar parameters.Here,we present the experimental generation of>60 MeV protons and>30 MeV u-1 carbon ions from sub-micrometre thickness Formvar foils irradiated with laser intensities>1021 Wcm2.Ions are accelerated by an extreme localised space charge field≥30TVm-1,over a million times higher than used in conventional accelerators.The field is formed by a rapid expulsion of electrons from the target bulk due to relativistically induced transparency,in which relativistic corrections to the refractive index enables laser transmission through normally opaque plasma.We replicate the mechanism on two different laser facilities and show that the optimum target thickness decreases with improved laser contrast due to reduced pre-expansion.Our demonstration that energetic ions can be accelerated by this mechanism at different contrast levels relaxes laser requirements and indicates interaction parameters for realising application-specific beam delivery.

全球地震危险性图与抗震设防烈度关系浅析

抗震设防烈度是建筑抗震设计的一项基本参数,许多国外工程建设项目由于所在国无可供执行或参照的抗震设计规范,使得项目前期的场地勘察与结构设计缺乏相应依据。文章介绍了全球地震模型开源平台发布的全球地震危险性图,通过分析其基准场地与国标场地类别的联系,探求全球地震危险性图地震动峰值加速度与抗震设防烈度的对应关系,为国内外工程建设项目的岩土工程勘察和抗震设计提供参考依据。

Effects of Accelerated Soil Erosion on Soil Nutrient Loss After Deforestation on the Loess Plateau

Soil erosion and nutrient losses on newly-deforested lands in the Ziwuling Region on the Loess Plateau of China were monitored to quantitatively evaluate the effects of accelerated soil erosion, caused by deforestation, on organic matter, nitrogen and phosphorus losses. Eight natural runoff plots were established on the loessial hill slopes representing different erosion patterns of dominant erosion processes including sheet, rill and shallow gully (similar to ephemeral gully). Sediment samples were collected after each erosive rainfall event. Results showed that soil nutrients losses increased with an increase of erosion intensity. Linear relations between the losses of organic matter, total N, NH4-N, and available P and erosion intensity were found. Nutrient content per unit amount of eroded sediment decreased from the sheet to the shallow gully erosion zones, whereas total nutrient loss increased. Compared with topsoil, nutrients in eroded sediment were enriched, especially available P and NH4-N. The intensity of soil nutrient losses was also closely related to soil erosion intensity and pattern with the most severe soil erosion and nutrient loss occurring in the shallow gully channels on loessial hill slopes. These research findings will help to improve the understanding of the relation between accelerated erosion process after deforestation and soil quality degradation and to design better eco-environmental rehabilitation schemes for the Loess Plateau.

Accelerating column leaching trial on copper sulfide ore

The main measures to accelerate leaching sulfide ore are large spraying intensity,manual oxygen supply,temperature control,and acclimated bacteria.The indoor experiment accelerating sulfide ore leaching detected the temperature during leaching process,dissolvability of oxygen,bacterial concentration,Cu concentration and slag grade.At the same time,this paper also analyzed the effect of four factors,which are bacterial diversity cultivation stage,spraying intensity,air supply,and whether to control temperature,on the leaching efficiency of copper.The results indicate that the oxygen content of leach solution has a close relationship with temperature but it is rarely affected by air supply.The bacterial concentration preserves from 106 to 107 mL^-1,and temperature has a great effect on the bacterial activity under the condition of proper temperature and oxygen supply,and the lack of nutrition prevents the bacterial concentration from rising in the late stage.The relationships of the copper leaching efficiency to temperature,air feed,and spraying intensity are directly proportional.The leaching efficiencies of the cultivated bacteria and acclimation bacteria are 1.2 and 1.4 times as large as that of the original bacteria.

High-Order Temporal Corrected Fields of Ultra-Short Laser Pulses and Laser-Driven Acceleration

Up to third-order temporal correction in terms of a small dimensionless temporal parameter ε=1/（ωoto） （ω0=ck0 the central oscillatory frequency, to the pulse duration of half period）, the field expressions of ultra-short focused laser pulses are explicitly presented. To evaluate the correction efficacy, electric amplitudes of zeroth-order and higher-order corrected fields are compared for different pulse durations. Furthermore, electron interaction with ultra-short laser pulses is simulated using both the zeroth-order and higher-order corrected field equations. Our simulation results show that the third-order correction terms should be considered for investigating the interaction if the laser pulse duration decreases to a few optical periods.

Energetic Laser-Ion Acceleration by Strong Charge-Separation Field

The laser-ion acceleration from the ultra-short and ultra-intense laser-matter interactions attracts more and more interest nowadays. When a laser pulse interacts with a target, relativistic electrons are generated in a period of few femtoseconds and driven away by the ponderomotive force, then a huge charge-separation field forms. In general cases, the ion acceleration is determined by this charge-separation field and the scale length of the plasma density. A general time-dependent solution is obtained to describe laser-plasma isothermal expansions into a vacuum, which is the fundamental theory of the laser-ion acceleration. It is adequate for non-quasi-neutral plasmas and different types of the scale length of the density gradient. The previous solutions are some special cases of our general solution. It is found that there exist both a compression layer of the ion velocity distribution and a potential well for sorue initial conditions. However, many unaccounted idiographic solutions, which may be used to reveal new mechanisms of ion acceleration, may be deduced from our general solutions.

A new type seismic intensity meter

A new type of seismic intensity meter based on MEMS accelerometer is introduced. It employs STM32FI07 as the data processing core and detects the changes of acceleration with triaxial MEMS LIS344ALH and uses ADS1248 for 24 bit data sampling. The test on vibration table shows that the linearity of the meter is δL = ± 1.4% , and the sensitivity is Kc = 0.9671V/g with zero deviation of 0.0043 g. The seismic intensity meter has the advantages of simple structure and stable performance and it is appropriate for intensive layout on a large scale.