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毫米波自由电子激光的数值模拟和实验的比较 总被引:2,自引:0,他引:2
从波导管毫米波自由电子激光器的设计要求出发,根据Livermore实验室FRED程序的物理思想,编制了空间三维的数值模拟程序(WAGFEL)。为了检验程序的可靠程度,结合ELF装置的实际参数,进行了数值模拟并和实验结果进行了比较。结果表明,把Wiggler磁场B_w增大300 Gs后,WAGFEL程序的模拟结果和Livermore实验室的实验结果基本符合。模拟使用的全部参数,除B_w增大300Gs外,都是ELF的实际参数。模拟时峰值磁场B_w=4050Gs,实验测量峰值磁场B_w=3720Gs,相差在8%左右。WAGFEL程序可以用来从事毫米波自由电子激光器的设计以及基本物理问题的研究。 相似文献
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The acceleration of electrons by using a Bessel-Gaussian (BG) beam in vacuum is studied. It is shown that the axial electric
field of a linearly or circularly polarized BG beam of order n = 1 can be used to accelerate electrons. The general features of the acceleration of electrons by using a linearly or circularly
polarized BG beam, such as the transversal and axial electric-field components, phase velocity, slippage distance, accelerating
potential, and energy gain etc., are analyzed. 相似文献
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S. N. Dolya 《Technical Physics》2014,59(11):1694-1697
Magnetic dipoles are accelerated by a running gradient of the magnetic field that is produced by sequentially energizing current-carrying turns. Magnetic dipoles d sh = 60 mm in diameter and l tot = 1 m in length are gasdynamically preaccelerated to velocity V in = 1 km/s, with which they are injected into the main accelerator. The turnover of the dipoles in the field of an accelerating pulse is prevented and focusing of dipoles is provided by directing the dipoles into a titanium tube. The weight of the dipoles is m = 2 kg, and they acquire final velocity V fin = 5 km/s over acceleration length L acc = 300 m. 相似文献
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A phase superposition approach for generating arbitrarily accelerating beams is proposed, where the superimposed phase is composed of multiple sub‐phases, each of which determines an independent sub‐beam or sub‐trajectory. Further, an effective algorithm is developed to improve the uniformity of the intensity along the arbitrary trajectory by introducing phase‐shift factors. Experimental results are consistent with numerical simulations. The proposed method can be extended to nonparaxial fields, and it also breaks the previous trajectory restrictions. The arbitrarily accelerating optical beams can pave the way for optically moving particles along a predefined trajectory. The property of such beams following arbitrary trajectories is likely to give rise to new applications in wave front control, flexible optical manipulation, and optical transport and guidance of particles. 相似文献
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The effect of accelerating stepwise on the jamming transition is investigated in the extended car-following model. The optimal velocity function is modified to take into account accelerating stepwise vehicles. It is shown that the multiple phase transitions occur on varying the car density. The multiple transitions change with the delay time. The flow-density curves and the velocity-headway curves are presented for various delay times. It is also shown that the multiple jamming transition lines are consistent with the neutral stability curves. The jamming transitions are closely related with the turning points of the optimal velocity function. 相似文献
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The beam transport design of a novel proton dielectric wall accelerator is introduced in this paper. The protons will be accelerated from 40 keV to nearly 1 MeV under an accelerating gradient that is as high as 20 MV/m. A consideration of the beam line as well as the transport simulation is presented. The influences of the injection timing jitter and the accelerating pulse timing jitter are also discussed. 相似文献
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本研究以拟南芥(Columbia野生型)干种子为材料,利用兰州重离子研究装置(HIRFL)产生的碳离子束对材料进行辐射处理,统计其存活率、根长、下胚轴长及每果荚种子数,以探讨不同传能线密度(Linear Energy Transfer,LET)的碳离子束辐照对拟南芥当代损伤效应的影响。结果表明,在相同LET辐射条件下,随着辐射剂量的增大,拟南芥的存活率、根长、下胚轴长度、每果荚种子数都呈现下降趋势。在相同剂量不同LET辐射处理情况下,随着LET的增大,存活率、根长、下胚轴长、每果荚种子数都显著下降,可见高LET辐射严重抑制了拟南芥的生长和发育。研究表明,当LET为50 keV/μm时,碳离子束辐射拟南芥干种子对应的最佳诱变剂量为200 Gy,为后续开展碳离子束辐射的诱变效率研究奠定了前期基础。Aimed to study the biological effects of carbon ion beams with different linear energy transfer (LET) values provided by Heavy Ion Research Facility in Lanzhou (HIRFL), dry seeds of Arabidopsis thaliana (Columbia-WT) were irradiated and a series of biological effects of postembryonic development, such as survival rate, primary root length, hypocotyls length and number of seeds per silique, were investigated. The results showed that, under the radiation condition of the same LET value, the survival rate, root length, hypocotyls length and number of seeds per silique were decreased with the increasing dose. In addition, under the radiation conditions with different LET values, but same dose, the extent of the decline of the survival rate, root length, hypocotyls length and number of seeds per silique were reinforced with the increasing LET. It was also found that high LET radiations inhibited the subsequent growth and development of Arabidopsis thaliana severely. In brief, it was suggested that the optimum dose of carbon ion beam with 50 keV/μm value on Arabidopsis thaliana dry seeds was 200 Gy. This research complemented the preliminary theoretical foundation for the comparative study of the highest mutation efficiency of carbon ion beam irradiations at IMP, CAS(Institute of Modern Physics, Chinese Academy of Sciences). 相似文献
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An operation model of a negative microlens array is demonstrated. The array consists of two kinds of materials with different refractive indices. First of all, a positive microlens array with 256×256 elements serving as a pattern is fabricated by argon ion beam etching on the quartz. The diameter and average corona height of the element are 28 and 0.638 μm, respectively. The spacing between two neighboring elements is 2 μm. In the second phase, after being coated by epoxy, the positive microlens array pattern is spun and baked, leading to a complex negative microlens array. Surface stylus measurement shows that the surface of the positive quartz microlens array is smooth and uniform. Focal length measurement of the negative microlens array indicates that the focal length region with −731±3 μm is in good agreement with the theoretical calculation value of −729 μm. 相似文献
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Nonlinear dynamics of higher-dimensional system for an axially accelerating viscoelastic beam with in-plane and out-of-plane vibrations 总被引:1,自引:0,他引:1
In this paper, the bifurcations and chaotic motions of higher-dimensional nonlinear systems are investigated for the nonplanar nonlinear vibrations of an axially accelerating moving viscoelastic beam. The Kelvin viscoelastic model is chosen to describe the viscoelastic property of the beam material. Firstly, the nonlinear governing equations of nonplanar motion for an axially accelerating moving viscoelastic beam are established by using the generalized Hamilton’s principle for the first time. Then, based on the Galerkin’s discretization, the governing equations of nonplanar motion are simplified to a six-degree-of-freedom nonlinear system and a three-degree-of-freedom nonlinear system with parametric excitation, respectively. At last, numerical simulations, including the Poincare map, phase portrait and Lyapunov exponents are used to analyze the complex nonlinear dynamic behaviors of the axially accelerating moving viscoelastic beam. The bifurcation diagrams for the in-plane and out-of-plane displacements via the mean axial velocity, the amplitude of velocity fluctuation and the frequency of velocity fluctuation are respectively presented when other parameters are fixed. The Lyapunov exponents are calculated to identify the existence of the chaotic motions. From the numerical results, it is indicated that the periodic, quasi-periodic and chaotic motions occur for the nonplanar nonlinear vibrations of the axially accelerating moving viscoelastic beam. Observing the in-plane nonlinear vibrations of the axially accelerating moving viscoelastic beam from the numerical results, it is found that the nonlinear responses of the six-degree-of-freedom nonlinear system are much different from that of the three-degree-of-freedom nonlinear system when all parameters are same. 相似文献
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Sand particles blown by wind cause serious environmental problems and many researchers are trying to understand the dynamic
properties of blown sand better. But the existing numerical approaches have not been able to simulate many important characteristics
of wind-sand flow. In this paper, the evolution and fluctuation properties of blown sand at a dynamic steady state are investigated
by using a more effective method. Using the LES (large eddy simulation) method for air phase movement and the DEM (discrete
element method) for solid phase movement along with the existing particle-bed splashing function, we have characterized the
whole movement property of the wind-sand system. The results indicate that the saturation time decreases with the inlet friction
velocity, and it gradually reaches the shortest saturation time of about 1s; the saturation length, which is about 14 m at
the usual wind velocity, first increases with wind velocity and then reaches a plateau; within the saturation length, the
sand transport rate at different positions varies with time; the sand transport rate of the stable wind-sand flow is non-uniform
with distance downwind and time, and has a notable correlation with the inflow friction velocity. 相似文献
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The gas-liquid upward flow was studied in a rectangular minichannel of 1.75×3.8 mm and length of 0.7 m. The experiments were
carried out within the range of the gas superficial velocity from 0.1 to 10 m/s and the liquid superficial velocity from 0.07
to 0.7 m/s for the co-current H2O/CO2 flow under the conditions of saturation. The method for the two-beam laser scanning of structure and determination of statistic
characteristics of the two-phase flow was worked through. The slug-bubble, slug, transitional, churn, and annular flows were
distinguished. The statistics characteristics of liquid and gas phases motion in a minichannel were obtained for the first
time including the velocities of phase motion. 相似文献
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研究了束团压缩中的高阶效应, 结果表明存在高阶项的压缩限制, 压缩后束团的长度比线性理论值长, 初始为均匀分布的束团较高斯分布更易压缩, 在相同的加速段与磁压缩器条件下, 其所获得的束团长度较短, 最后作了数值计算, 结果与理论相符. 相似文献
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We investigated vapor phase epitaxy-grown ZnO nanowires on a Si substrate by scanning electron microscopy. These investigations show that there are single nanowires and ensembles of nanowires, among which we found straight and bend, perfect and non-perfect nanowires, as well as nanowires with clean surfaces and surfaces with the dark spots and features. After focused ion beam polishing and milling we found that nanowires are homogeneous. The sizes of the nanowires were determined: the length is about 2–24 μm, and the width and height are about 200–500 nm. 相似文献
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介绍了介质壁加速器(DWA)的原理和几种可能实现的结构。通过对多层介质圆柱的平面波电磁散射的研究,用FORTRAN语言编写程序计算和分析了DWA加速管三层介质柱体结构的平面波电磁散射的散射宽度与几何结构参数、材料参数的关系,用以优化设计介质壁加速管结构。计算结果表明:当加速管材料和等势环介电常数一定时,平面波电磁散射宽度随半径增大而增大;当加速管内外径一定时,加速管材料和等势环介电常数增大时散射宽度变化不明显,但最小散射宽度显著减小。当加速管半径和材料一定时,总能找到使散射宽度达到最小的等势环介质厚度。 相似文献
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Beam dynamics and RF design have been performed of a new type trapezoidal IH-RFQ operating at 104 MHz for acceleration of 14C+ in the framework of RFQ based 14C AMS facility at Peking University. Low energy spread RFQ beam dynamics design was approached by the method of internal discrete bunching. 14C+ will be accelerated from 40 keV to 500 keV with the length of about 1.1 m. The designed transmission efficiency is better than 95% and the energy spread is as low as 0.6%. Combining the beam dynamics design, a trapezoidal IH-RFQ structure was proposed, which can be cooled more easily and has better mechanical performance than traditional RFQ. Electromagnetic field distribution was simulated by using CST Microwave Studio (MWS). The specific shunt impedance and the quality factor were optimized primarily. 相似文献