共查询到20条相似文献,搜索用时 678 毫秒
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给出了高能脉冲X射线能谱测量的基本原理及实验结果.采用Monte-Carlo程序计算了高能光子在能谱仪中每个灵敏单元内的能量沉积,利用能谱仪测量了"强光Ⅰ号"加速器产生的高能脉冲X射线不同衰减程度下的强度,求解得到了具有时间分辨的高能脉冲X射线能谱,时间跨度57ns,时间步长5ns,光子的最高能量3.0MeV,平均能量1.04MeV,能量在0.2—0.9MeV之间的光子数目最多,占46.5%.也利用二极管的电压电流波形理论计算了光子的能谱,并与利用能谱仪测得的能谱进行了比较,两种方法所得结果基本一致. 相似文献
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理论分析了收集极中运动电子的失能机制和电子能量对电子束能量沉积的影响,用蒙特卡罗方法计算了不同能量下入射电子的能量沉积分布,分析了电子能量对电子束在收集极中能量沉积的影响,并据此提出了提高收集极耐电子束轰击能力的两种途径。结果表明:激发和电离是收集极中入射电子的主要失能机制;电子的能量越高,在材料中的穿透能力越强,收集极中被收集电子束的最大能量沉积密度越低。综合考虑束流密度分布对能量沉积的影响,可通过两种途径来提高收集极耐电子束轰击的能力:一是通过结构设计增大电子束的收集面积,减小收集极上被收集电子束的束流密度;二是设计高阻抗器件,增大被收集电子束的电子能量,减小收集极上被收集电子束的束流密度。 相似文献
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T. K. Rebane 《Optics and Spectroscopy》2000,88(1):22-27
The dependence of the energy of three-particle molecules on their masses is examined. It is shown that such molecules with the same values of the ratio of the reduced masses for motion in a “fast” and “slow” Jacobi coordinates have the property of adiabatic similarity: In the adiabatic approximation, their energies are proportional to the reduced masses. This allows information on the energy of molecules symmetric in the masses of particles to be extended to asymmetric molecules adiabatically similar to the symmetric molecules. For molecules with arbitrary masses of the particles, an analytic expression for the adiabatic energy and a formula approximating the exact energy are constructed using the principle of adiabatic similarity. Along with the adiabatic energy, which is the lower bound of the exact energy, a simple procedure is considered for determining the upper bound of the energy of asymmetric molecules from the energy of their symmetric counterparts. Based on these results, values of the lower and upper energy bounds are calculated and an approximation of the exact energy is obtained for 43 three-particle molecular systems. 相似文献
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Yewan Ma Hansen Chang Zhaowang Wu Yanyan Jiang Juan Li Xunchang Yin Quanjin Liu Lihua Zhang 《声与振动》2019,53(4):139-149
The energy of a spring with a well-distributed mass ms is theoretically studied in this paper. The solution of the wave equation is derived in detail, and then the kinetic energy and potential energy of the spring are studied with the wave
equation, as well as the kinetic energy of the oscillating mass M. The kinetic energy and potential energy of the spring, and total energy are numerically simulated for different ratios ms/M with considering the spring’s mass, which
makes the property of energy of the oscillating system understood easily. 相似文献
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A. S. Parshin A. Yu. Igumenov Yu. L. Mikhlin O. P. Pchelyakov V. S. Zhigalov 《Physics of the Solid State》2016,58(5):908-914
The inelastic electron scattering cross section spectra of Fe have been calculated based on experimental spectra of characteristic reflection electron energy loss as dependences of the product of the inelastic mean free path by the differential inelastic electron scattering cross section on the electron energy loss. It has been shown that the inelastic electron scattering cross-section spectra have certain advantages over the electron energy loss spectra in the analysis of the interaction of electrons with substance. The peaks of energy loss in the spectra of characteristic electron energy loss and inelastic electron scattering cross sections have been determined from the integral and differential spectra. It has been shown that the energy of the bulk plasmon is practically independent of the energy of primary electrons in the characteristic electron energy loss spectra and monotonically increases with increasing energy of primary electrons in the inelastic electron scattering cross-section spectra. The variation in the maximum energy of the inelastic electron scattering cross-section spectra is caused by the redistribution of intensities over the peaks of losses due to various excitations. The inelastic electron scattering cross-section spectra have been analyzed using the decomposition of the spectra into peaks of the energy loss. This method has been used for the quantitative estimation of the contributions from different energy loss processes to the inelastic electron scattering cross-section spectra of Fe and for the determination of the nature of the energy loss peaks. 相似文献
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基于协变密度泛函(CDF)理论,核物质四阶对称能可以被分解为动能部分,同位旋单态势能部分以及同位旋三重态势能部分。交换项的引入明显改变了同位旋单态势能部分和同位旋三重态势能部分的密度行为,特别是来自同位旋标量介子-核子耦合道的交换项贡献提供了一个压制作用。作为一种有益的尝试,引入广义的对称能,可以更直观地统一描述核物质各阶对称能效应。The density dependence of nuclear fourth-order symmetry energy S4 is studied within the covariant density functional (CDF) theory in terms of the kinetic energy, isospin-singlet, and isospin-triplet potential energy parts of the energy density functional. When the Fock diagram is introduced, it is found that both isospin-singlet and isospin-triplet components of the potential energy plays important roles in determining the fourth-order symmetry energy. Especially, an extra suppression, which comes from the Fock terms via isoscalar meson-nucleon coupling channels, is revealed in the isospin-triplet potential part of the fourth-order symmetry energy. As an useful attempt, the generalized symmetry energy is introduced to describe the various orders of nuclear symmetry energies in a visual and self-consistent way. 相似文献
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《Physics letters. A》2006,359(6):597-602
We investigate the exact solution of BCS pairing model using direct diagonalization of Fock space. By the data analysis and numerical calculation, we verify the symmetry between energy spectrum of Fock subspaces, obtain the common structure features of energy gaps and energy bands in Hamiltonian spectrum of reduced model, propose the formula to estimate the lowest energy levels in all of the subspaces of reduced model, and suggest a scheme to estimate the respective energy spectrum which can reveal the structure of energy spectrum of pairing model. 相似文献
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Karan Singh Vinayak Suneel Kumar 《The European Physical Journal A - Hadrons and Nuclei》2011,47(11):144
The effect of density-dependent symmetry energy on elliptical flow is studied using the isospin-dependent quantum molecular
dynamics model (IQMD). We have used the reduced isospin-dependent cross-section with hard (H) equation of state to study the
sensitivity of the elliptical flow to symmetry energy in the energy range 50-1000MeV/nucleon. The elliptical flow becomes
zero at a particular energy termed as transition energy. A systematic effort has been made to pin down the transition energy
for the density-dependent symmetry energy. 相似文献
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利用嵌入原子方法的原子间相互作用势,通过分子动力学模拟,详细研究了贵金属原子在Pt (111)表面的低能溅射现象.模拟结果显示:对于垂直入射情况,入射原子的质量对Pt (11 1)表面的溅射阈值影响不大.当入射原子的能量小于溅射阈值时,入射原子基本以沉积为主 ;当入射原子的能量大于溅射阈值时,溅射产额随入射原子能量的增加而线性增大;当入射 原子能量达到200 eV时,各种入射原子的溅射产额都达到或接近1,此时入射原子主要起溅 射作用.溅射原子发射的角分布概率和溅射花样与高能溅射相类似.研究表明:与基于二体碰 撞近似的线性级联溅射理论不同,当入射原子能量大于溅射阈值时,低能入射原子的溅射产 额正比于入射原子的约化能量和入射原子与基体原子的质量比.通过对低能入射原子的钉扎 能力分析,提出了支配低能溅射的入射原子反射物理机理.
关键词:
分子动力学模拟、低能溅射 相似文献
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高能激光能量计校准方法研究 总被引:1,自引:3,他引:1
给出了一种绝对式高能激光能量计光电校准方法.该方法以大功率灯作为校准光源,通过测量灯两端的电压以及电流获得电能值,去掉灯所消耗的热能,得到灯所发出的光能.所设计平板能量计将大功率灯密封在高能激光能量计内,光能全部被能量计吸收.根据能量计输出值以及光能值便可实现能量计光电校准.结果表明,能量计光电校准不确定度约为1.5%. 相似文献
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采用平面波展开、幺正变换和变分相结合的方法推导出有限深势阱里量子盘中极化子的基态能量公式.采用极化子单位进行数值计算,结果表明极化子的基态能量随势垒高度和势垒宽度的增大而增大,原因是势垒愈高、愈宽,电子穿透势垒的可能性愈小,导致电子能量增大,进而导致极化子基态能量增大.数值计算结果还表明极化子的基态能量随量子盘有效受限长度和量子盘半径的增大而减小;声子效应导致极化子能量较电子能量低. 相似文献
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The exciton energies of rare earth oxides (Ln2O3) have rarely been calculated by the theory. Experimentally, the blue-shift of exciton energy in nanocrystals deviates from the traditional size confinement effect. Herein, the dependence of the ground-state energy of an exciton in Y2O3 spheres on particle radius was calculated by using a variational method. In the model, an exciton confined in a sphere surrounded by a dielectric continuum shell was considered. The ground-state energy of exciton comprises kinetic energy, coulomb energy, polarization energy and exciton–phonon interaction energy. The kinetic and coulomb energy were considered by the effective mass and the dielectric continuum and the exciton–phonon interaction energy was given by the intermediate coupling method. The numerical results demonstrate that the present model is roughly consistent with the experimental results. The confinement effect of the kinetic energy is dominant of the blue-shift of the exciton energy in the region of R < 5 nm, while confinement effect of the coulomb energy is dominant of the blue-shift of the exciton energy in the region of R > 5 nm. The polarization energy contributes largely to the exciton energy as the particle size is smaller than ~ 10 nm, while the exciton–phonon interaction energy takes only a little contribution in all the range. 相似文献
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抛物量子线中束缚极化子激发态的性质 总被引:1,自引:0,他引:1
本文研究库仑场对抛物量子线中强耦合束缚极化子激发态性质的影响。采用Huybrechts线性组合算符和幺正变换的方法计算了抛物量子线中强耦合束缚极化子的第一内部激发态能量、激发能量和振动频率。数值计算表明:强耦合束缚极化子的第一内部激发态能量和激发能量都随约束强度的增加而增大;但第一激发态能量随库仑束缚势的增加而减少,而激发能量随库仑束缚势的增加而增大;振动频率 随约束强度和库仑束缚势增加而增大。 相似文献
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基于靶背鞘层加速机制(TNSA)产生的质子束具有宽能谱的特性,限制了其应用范围。为了产生准单能质子束,研究了基于直线加速器射频腔结构的质子能谱优化方法。在给定射频腔电压和频率情况下,计算了腔间距随优化能量的变化关系,并针对不同优化能量设计了不同大小的腔间距和腔数。在给定腔数情况下,发现只在某个能量附近可以获得单能性最好的单能峰。对能量接受范围进行了分析,要实现最终2%的能散,进入射频腔的质子束能散不能大于15%,并分析了射频腔频率对能量接受范围的影响。最后对PIC模拟得到的半高全宽为15%的一个能谱进行优化,获得了谱宽小于2%的准单色质子能谱。
. 相似文献
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利用一维三温辐射磁流体力学程序对氖气和铝丝阵Z箍缩内爆过程中的能量转换过程进行了详细的数值研究,发现在内爆过程中离子和电子之间的碰撞能量交换是最主要的能量交换过程,其次是电子和光子之间的光电过程和轫致过程,而康普顿散射过程中的能量交换可以忽略不计;辐射出的x射线主要是在光电激发和光电复合过程中产生的,其次是在轫致辐射过程和康普顿散射过程中产生的.理论分析表明,辐射出的x射线能量可以超过,也可能小于其等离子体最大动能.数值模拟结果表明,在氖气Z箍缩中,辐射出的x射线能量没有超过其等离子体最大动能,而在铝丝阵列内爆中,辐射出的x射线能量超过了其等离子体最大动能,但小于磁压所做的功;在整个Z箍缩过程中欧姆加热能量是较小的.
关键词:
Z箍缩
能量转换
x射线辐射 相似文献
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This paper establishes a new formulation of the energy exchanges between the different parts of total energy. The decomposition uses the Reynolds averaging. This leads to a ternary decomposition of kinetic energy into the turbulence kinetic energy, the mean kinetic energy and the mixed kinetic energy, acting as an exchange term between the mean and turbulent motion. The formulation is then extended to distinguish a mean and fluctuating density part of each part of total energy. The formulation thus includes the mean density turbulence kinetic energy, product of the mean density and the half-trace of the velocity fluctuation correlation tensor. Its evolution equation is given in the spectral domain. 相似文献