Design of a compact beam transport system for laser-driven proton therapy

We put forward a new design of a compact beam transport system for intense laser-driven proton therapy,where instead of using conventional pulsed solenoids,our design relies on a helical coil irradiated by a nanosecond laser pulse to generate strong magnetic fields for focusing protons.A pair of dipole magnets and apertures are employed to further filter protons with large divergences and low energies.Our numerical studies combine particle-in-cell simulations for laser-plasma interaction to generate high-energy monoenergetic proton beams,finite element analysis for evaluating the magnetic field distribution inside the coil,and MonteCarlo simulations for beam transport and energy deposition.Our results show that with this design,a spread-out Bragg peak in a range of several centimeters to a deep-seated tumor with a dose of approximately 16.5 cGy and fluctuation around 2% can be achieved.The instantaneous dose rate reaches up to 10^(9)Gy/s,holding the potential for future FLASH radiotherapy research.

Retail Brand Building Through Promotional Communication： A Study That Focuses on Category Killers Promotional Flyers

Strong competition in retail distribution and the development of new purchasing options for the consumer generate a growing need to strengthen the retailers＇ brand image using all the communication elements, with promotional flyers being one of the most important ways to do this. Promotional flyers make-up 5.1% of the money spent on communication and rank third place in terms of importance for retailers. The aim of this investigation work is to focus on analysing the utility of a promotional tool, such as a flyer, to fulfil a strategic objective, like creating a retail brand image, within a modern dynamic sector that is growing fast, such as Category Killers. Two sources of information have been used to carry out the research. On the One hand, a survey conducted on those responsible for the definition and execution of the promotional plan, and on the other hand, the accumulation and analysis of all the flyers issued into the market thought-out a year by those retailers which belong to this format, in order to conduct a study of seven defined image indicators. This information has been largely analyzed using multidimensional scaling method and chi-square test. As a result, we have managed to gather the differential elements in flyers execution between those retailers that prize the communications of image attributes and those retailers which concentrate on communicating price. The first group makes greater use of promotional theme related flyers, and shows greater differentiation in both product assortment and the depth of the range being communicated.

Investigation of system parameters towards safer impact based shock-to-detonation transition in a novel laser driven flyer plate prototype

Laser driven flyer plate technology offers improved safety and reliability for detonation of explosives in industrial applications ranging from mining and stone quarrying to the aerospace and defense industries.This study is based on developing a safer laser driven flyer plate prototype comprised of a laser initiator and a flyer plate subsystem that can be used with secondary explosives.System parameters were optimized to initiate the shock-to-detonation transition(SDT)of a secondary explosive based on the impact created by the flyer plate on the explosive surface.Rupture of the flyer was investigated at the mechanically weakened region located on the interface of these subsystems,where the product gases from the deflagration of the explosive provide the required energy.A bilayer energetic material was used,where the first layer consisted of a pyrotechnic component,zirconium potassium perchlorate(ZPP),for sustaining the ignition by the laser beam and the second layer consisted of an insensitive explosive,cyclotetramethylene-tetranitramine(HMX),for deflagration.A plexiglass interface was used to enfold the energetic material.The focal length of the laser beam from the diode was optimized to provide a homogeneous beam profile with maximum power at the surface of the ZPP.Closed bomb experiments were conducted in an internal volume of 10 cm^(3) for evaluation of performance.Dependency of the laser driven flyer plate system output on confinement,explosive density,and laser beam power were analyzed.Measurements using a high-speed camera resulted in a flyer velocity of 670±20 m/s that renders the prototype suitable as a laser detonator in applications,where controlled employment of explosives is critical.

Poloidal magnetic field reconstruction by laser-driven ion-beam trace probe in spherical tokamak

The poloidal magnetic field( B_(p)) plays a critical role in plasma equilibrium, confinement and transport of magnetic confinement devices. Multiple diagnostic methods are needed to complement each other to obtain a more accurate B_(p) profile. Recently, the laser-driven ion-beam trace probe(LITP) has been proposed as a promising tool for diagnosing B_(p) and radial electric field( E_(r)) profiles in tokamaks [Yang X Y et al 2014 Rev. Sci. Instrum. 85 11E429]. The spherical tokamak(ST) is a promising compact device with high plasma beta and naturally large elongation. However, when applying LITP to diagnosing B_(p) in STs, the larger B_(p) invalidates the linear reconstruction relationship for conventional tokamaks, necessitating the development of a nonlinear reconstruction principle tailored to STs. This novel approach employs an iterative reconstruction method based on Newton's method to solve the nonlinear equation. Subsequently,a simulation model to reconstruct the B_(p) profile of STs is developed and the experimental setup of LITP is designed for EXL-50, a middle-sized ST. Simulation results of the reconstruction show that the relative errors of B_(p) reconstruction are mostly below 5%. Moreover, even with 5 mm measurement error on beam traces or 1 cm flux surface shape error, the average relative error of reconstruction remains below 15%, initially demonstrating the robustness of LITP in diagnosing B_(p) profiles in STs.

Multi-layer phenomena in petawatt laser-driven acceleration of heavy ions

Laser-accelerated high-flux-intensity heavy-ion beams are important for new types of accelerators.A particle-in-cell program(Smilei) is employed to simulate the entire process of Station of Extreme Light(SEL) 100 PW laser-accelerated heavy particles using different nanoscale short targets with a thickness of 100 nm Cr, Fe, Ag, Ta, Au, Pb, Th and U, as well as 200 nm thick Al and Ca. An obvious stratification is observed in the simulation. The layering phenomenon is a hybrid acceleration mechanism reflecting target normal sheath acceleration and radiation pressure acceleration, and this phenomenon is understood from the simulated energy spectrum,ionization and spatial electric field distribution. According to the stratification, it is suggested that high-quality heavy-ion beams could be expected for fusion reactions to synthesize superheavy nuclei. Two plasma clusters in the stratification are observed simultaneously, which suggest new techniques for plasma experiments as well as thinner metal targets in the precision machining process.

英孚发布创意英语教材High Flyers

为进一步激发7至9岁儿童学习英语的主动性,英孚教育发布了由多国教育人士共同创作的创意教材。近日,《留学》应邀参加英孚教育在北京召开的媒体体验会,亲身感受了一套为7-9岁儿童量身定做的英语教材。这套名为"High Flyers"的教材研发历时三年,由多国教育界人士共同参与创作完成。英孚教育青少儿英语执行副总裁白皎宇告诉《留学》,High Flyers教材及课程引入了个性鲜明的动画人物,加入了多个实用的对话情景。

Theoretical Model for Calculating Electric-Power Curves Depicting Accelerated Flyer by Exploding Foil

A theoretical model for calculating electric-power curves of small-size foil during its electrical explosion is given.This technique is based on temperature dependence of foil conductivity.After taking into account the energy conversion of the foil explosion,the power-time curve is applied to the hydrodynamic code.One-dimensional numerical simulations of electric-explosion driving flyers are performed using this code.Calculated flyer velocities lie within ±8% of experimental data from Lawrence Livermore National Laboratory （LLNL）,and simulated history curves of flyer velocities coincide well with those measured using velocity interferometer system for any reflector （VISAR）,indicating a helpful work for design optimization of slapper detonators.

Calibration of CR-39 solid-state track detectors for study of laser-driven nuclear reactions

It is of particular interest to investigate nuclear fusion reactions generated by high-intensity lasers in plasma environments that are similar to real astrophysical conditions.We have experimentally investigated2H(d,p)3H,one of the most crucial reactions in big bang nucleosynthesis models,at the Shenguang-Ⅱlaser facility.In this work,we present a new calibration of CR-39 solidstate track detectors,which are widely employed as the main diagnostics in this type of fusion reaction experiment.We measure the dependence of the track diameter on the proton energy.It is found that the track diameters of protons with different energies are likely to be identical.We propose that in this case,the energy of the reaction products can be obtained by considering both the diameters and gray levels of these tracks.The present results would be very helpful for analyzing the2 H(d,p)3H reaction products recorded with the same batch of CR-39 solid-state track detectors.

Spatial and spectral measurement of laser-driven protons through radioactivation

The simultaneous measurement of the spatial profile and spectrum of laser-accelerated protons is important for further optimization of the beam qualities and applications.We report a detailed study regarding the underlying physics and regular procedure of such a measurement through the radioactivation of a stack composed of aluminum,copper,and CR-39 plates as well as radiochromic films(RCFs).After being radioactivated,the copper plates are placed on imaging plates(IPs)to detect the positrons emitted by the reaction products through contact imaging.The spectrum and energy-dependent spatial profile of the protons are then obtained from the IPs and confirmed by the measured ones from the RCFs and CR-39 plates.We also discuss the detection range,influence of electrons,radiation safety,and spatial resolution of this measurement.Finally,insights regarding the extension of the current method to online measurements and dynamic proton imaging are also provided.

CALCULATION AND MEASUREMENT OF DYNAMIC EXPANSION OF ROVING FLYER

Roving flyer is an important part of roving frame. Its dynamic expansions affect the quality of rove greatly. The expansions are calculated by means of the general program SAP84 based on finite element method in this paper. Its measuring principle and usage are also described. The results of calculating and measuring are identical. The method presented in the paper is effective for studying the properties of roving flyer.

Method of Testing the Flyer Sensitivity of Explosives

By means of Mylar flyer shock explosives driven by electric gun, the method of testing the flyer initiation sensitivity of explosives is studied, and some experiments are done. The experimental results show that the test method established is correct, which is very important and instructive to study and evaluate the safety and reliability of explosives. For the moment, the test should be researched and discussed further..

Laser-driven flier impact experiments at the SG-III prototype laser facility

Laser-driven flier impact experiments have been designed and performed at the SG-III prototype laser facility. The continuum phase plate（CPP） technique is used for the 3 ns quadrate laser pulse to produce a relatively uniform irradiated spot of 2 mm. The peak laser intensity is 2.7×10^13W/cm^2 and it accelerates the aluminum flier with a density gradient configuration to a high average speed of 21.3 km/s, as determined by the flight-of-time method with line VISAR. The flier decelerates on impact with a transparent silica window, providing a measure of the flatness of the flier after one hundred microns of flight. The subsequent shock wave acceleration, pursuing, and decay in the silica window are interpreted by hydrodynamic simulation. This method provides a promising method to create unique conditions for the study of a material＇s properties.

γ-Fe Nano-particles from Fe(CO)_5 by CW CO_2 Laser-driven

γ-Fe nano-particles with size of 20-40 nm were produced by SF6-sensitized CW CO2 laser-induced gaseous pyrolysis of Fe(Co) 5, The γ-Fe stabte in reaction zone at above 910℃ was formed.The rapid quenching prevents from the γ-Fe transforming to α-Fe as rapidly cooling from high temperature to room temperature, The characteristics of the particles were examined at room temperature by TEM. electron diffraction and XRD. It was proved that about 70% of γ-Fe phase in the particles was present. In addition. the lattice constant of the γ-Fe was 0.364 nm in place of 0.360 nm

Topology optimization of on-chip integrated laser-driven particle accelerator

Particle accelerators are indispensable tools in both science and industry.However,the size and cost of conventional RF accelerators limits the utility and scope of this technology.Recent research has shown that a dielectric laser accelerator(DLA)made of dielectric structures and driven at optical frequencies can generate particle beams with energies ranging from MeV to GeV at the tabletop level.To design DLA structures with a high acceleration gradient,we demonstrate topology optimization,which is a method used to optimize the material distribution in a specific area based on given load conditions,constraints,and performance indicators.To demonstrate the effectiveness of this approach,we propose two schemes and design several acceleration structures based on them.The optimization results demonstrate that the proposed method can be applied to structure optimization for on-chip integrated laser accelerators,producing manufacturable structures with significantly improved performance compared with previous size or shape optimization methods.These results provide new physical approaches to explore ultrafast dynamics in matter,with important implications for future laser particle accelerators based on photonic chips.

Analysis of the Intrinsic Uncertainties in the Laser-Driven Iron Hugoniot Experiment Based on the Measurement of Velocities

One of the most challenging tasks in the laser-driven Hugoniot experiment is how to increase the reproducibility and precision of the experimental data to meet the stringent requirement in validating equation of state models. In such cases, the contribution of intrinsic uncertainty becomes important and cannot be ignored. A detailed analysis of the intrinsic uncertainty of the aluminum-iron impedance-match experiment based on the measurement of velocities is presented. The influence of mirror-reflection approximation on the shocked pressure of Fe and intrinsic uncertainties from the equation of state uncertainty of standard material are quantified, Furthermore, the comparison of intrinsic uncertainties of four different experimental approaches is presented. It is shown that, compared with other approaches including the most widely used approach which relies on the measurements of the shock velocities of AI and Fe, the approach which relies on the measurement of the particle velocity of Al and the shock velocity of Fe has the smallest intrinsic uncertainty, which would promote such work to significantly improve the diagnostics precision in such an approach.

Swiss Innovation Week 2019:Home of Drones,the New High Flyer of Swiss Industry

Following the successful Swiss Innovation Week(SIW)held in July 2018,the Embassy of Switzerland in China launches its 2nd edition from 12 to 14of June 2019.With Swiss drones as the brand-new theme,Switzerland’s drone ecosystem and innovation in the field of flying robots were present.According to various rankings,Switzerland is one of the most innovative countrie s in the world and also one of the most competitive co untries.

Experimental Study on the Small Flyer Initiating Behavior of Fine-grained Explosives

The initiating behavior of fine-grained explosives by small flyer is studied. The diameter of small flyer in this device is 1mm. The test results indicate that the granularity of explosives has great effect on its flyer initiating sensitivity.The flyer initiating sensitivity of the fine-grained explosives is higher and the critical initiating energy is lower than that of common explosives. For common explosive, the flyer initiating sensitivity increases as the density is reduced. But for the fine-grained explosive, the test results are exactly opposite.

Laser-Driven Light Sources for Nanometrology Applications

Laser-driven light sources(LDLS)have ultrahigh-brightness and broad wavelength range.They are ideal radiation sources for optical metrology tools for advanced process control in semiconductor manufacturing.LDLS sources,with their advantages of 170 nm to 2100 nm wavelength range,have been widely adopted and are being used in volume manufacturing for spectroscopic ellipsometry(SE),spectroscopic scatterometry(SS),and white light interferometry(WLI)applications.Such applications are used to measure critical dimensions(CD),overlay(OVL),and film thickness.

金属桥箔电爆炸驱动飞片过程数值模拟研究

为研究金属桥箔电爆炸等离子体驱动飞片全过程中飞片的性能特征和影响规律,建立了金属桥箔电爆炸驱动飞片全过程的多相流数值计算模型,并进行了数值模拟计算.计算中,利用了相变分数描述金属桥箔由固相到等离子体相的相态转变,采用了考虑粒子数目变化及粒子间库仑作用的高温高压等离子体状态方程描述电爆炸等离子体的形成和运动行为,采用了动网格模型描述飞片的运动.将计算结果与实验结果进行对比分析,计算得到的飞片速度值与实验值的误差小于5%,表明计算模型的准确性较好.基于该计算模型,对总面积相同的双体阵列桥箔和单体桥箔电爆炸等离子体驱动飞片过程进行了数值模拟,计算结果表明,由于阵列桥箔电爆炸过程中等离子体和冲击波的叠加汇聚作用,提高了能量转化效率,使得等离子体及冲击波流场对飞片的驱动力增加,从而提高了飞片的速度.等离子体流场对飞片表面的烧蚀厚度约为0.1μm,飞片的完整性较好.

环境温度对TATB/RDX传爆药起爆及驱动性能的影响

为了获得环境温度对TATB/RDX传爆药起传爆性能及驱动性能的影响特性,采用激光多普勒测速技术及瞬态太赫兹波多普勒干涉测速技术,对TATB/RDX传爆药在隔层起爆条件下的起爆、传播及驱动性能开展实验研究,获取了-45~70℃温度环境中TATB/RDX传爆药的到爆轰距离、爆轰反应区时间宽度、爆轰传播速度及驱动飞片的飞行速度曲线。结果表明:TATB/RDX传爆药的到爆轰距离及爆轰反应区时间宽度随环境温度的降低均近乎呈线性增长趋势;爆轰传播速度随环境温度的降低而逐渐提高;驱动飞片的速度随环境温度的变化特性在飞片主体-层裂层融合前后存在明显不同。