延时注入对驻波加速管X线输出量的影响

一、引言驻波加速管工作于脉冲方式时,在每个微波脉冲的开始和结束时,加速管内场强有一个建成和衰减的过渡过程,在过渡过程中,加速场强随时间不断变化,如果电子束和微波功率同时注入及馈入驻波加速管,则将有较多的低能电子产生,它们不仅增加加速管的负载,使输出能谱变坏,而且这部份低能电子对X线输出量的贡献也不大。由于过渡过程的     

流速加速腐蚀引起的碳钢管壁减薄

论述了核电厂高能碳钢系统中流速加速腐蚀（ＦＡＣ）引起的碳钢管壁减薄,介绍了问题的出现,ＦＡＣ的腐蚀机理及其影响因素,ＣＡＮＤＵ ６核电站一回路出口供水管管壁减薄的原因,以及秦山三期ＣＡＮＤＵ机组解决出口供水管管壁减薄的改进措施,以保证核电厂安全可靠经济地运行。     

超灵敏小型回旋加速器质谱计交替加速的实验研究

系统介绍了在SMCAMS中为了精确测量14C而采用过的各种交替加速类型.     

中子输运计算的角度多重网格加速和L-W外推加速技术

把角度多重网格(ANMG)加速方法及Lyusternik-Wagner(L-W)外推加速技术应用于三维多群离散纵标三角形节块稳态中子输运数值计算程序(DNTR).一系列输运问题的数值结果表明:ANMG加速方法具有较好的加速效果,且对强各向异性散射和强散射比问题有很强的适应性.在ANMG加速方法的基础上增加L-W外推加速技术后,可以使整体加速效果更加显著.     

聚变堆两种候选钛合金的拉伸和疲劳性能

钛合金被选择为聚变反应堆的第一层围筒、再生区和磁性线圈的结构材料。钛合金之所以受到青睐,是由于其本身的高比强度、低弹性模量和低膨胀趋势,以及在受到辐照后其活性会很快降低等原因。此外,还因为钛合金有极好的耐蚀性和较好的可焊性,甚至在较厚的区域可焊性也很好。再者,钛合金的热应力参数很低,所以也适合作为承载热应力的部件。α相的钛合金被认为具有更好的耐辐照脆化性能,而（α＋β）相的钛合金则对氢脆具有最大的容许限度。在本项研究中,采用了这两个系列中的两种典型的工业用钛合金：Ti5Al2．4Sn和Ti6Al4V。报道了室温和450℃时的拉伸性能。在350℃条件下,开展了总应变范围为0．8％－2％的应变控制下的低周疲劳试验和分析。而且,还对两种合金变形之前和变形之后的微观组织进行了观测。两种合金都表现出了极好的力学性能,其力学性能与铁基马氏体钢的相当或者是更高。     

放射性离子束的产生和加速

研制了一条次级放射性束流线 ,产生放射性核束11C ,17F ,7Be,13N ,6 He。利用所获的放射性核束7Be,成功地完成了7Be(d ,n) 8B反应的角分布测量。采取离线方法产生和加速了放射性核束6 4Cu ,在实验靶上获 1.2× 10 5ions·s- 1(80MeV) ,完成了6 4Cu库仑激发实验研究。     

Cluster size effect on reactive sputtering by fluorine cluster impact using molecular dynamics simulation

The mechanism of high-yield sputtering induced by reactive cluster impact was investigated using molecular dynamics (MD) simulations. Various sizes of fluorine clusters were radiated on clean silicon surface. At an incident energy of 1 eV/atom, F atom and F₂ molecule are only adsorbed on the surface and sputtering of Si atom does not occur. However, fluorine cluster, which consists of more than several tens molecules causes sputtering. In this case, most of Si atoms are sputtered as fluorinated material such as SiF_x. This effect is due to the fact that cluster impact induces high-density particle and energy deposition, which enhances both formation of precursors and desorption of etching products. The deposition of atoms and energy becomes denser as the incident cluster size increases, so that larger clusters have shown higher sputtering yield.     

Integrated inertial fusion energy chamber dynamics and response

This paper presents results of three-dimensional hydrodynamics simulations of the flow inside a model inertial fusion energy (IFE) fusion chamber. Turbulence modeling employing the large-eddy simulation approach is used to estimate the gas dynamics, state, and mixing after a sufficiently large number of target ignitions. The rich radiation-flow physics that takes place immediately after the lasers hit the hohlraum is modeled separately using a high-fidelity one-dimensional model, which provides reference conditions for the complex geometry three-dimensional turbulence simulations. The IFE geometry includes optical ports and recirculation openings as well as a duct to evacuate the debris produced after each energy deposition (as a model of a laser shot). Furthermore, a selected set of sensitivity studies are conducted to estimate the effect of uncertainty in radiative properties of the Xenon gas at the prevalent conditions in the chamber. The results provide guidance regarding the turbulence conditions in the chamber, which seem to have entered a decay state immediately before a new shot takes place. Computational estimates of the density variability within the chamber as well as pressure history at the approximate location of the laser optical ports is presented among other turbulence statistics.     

低温条件下金属薄膜外延生长过程中瞬时扩散机制的研究

采用分子动力学方法和混合的紧束缚势模拟了Ｃｕ在Ｃｕ（１００）表面外延生长过程的初始阶段段。重点研究低温上外延表面原子的瞬时扩散机制，对瞬时扩散运动进行分类检验，并定量报道了各类瞬时扩散过程在低温条件下的相对发生比例，由此得知，轰击引起的级联扩散机制对外延表面原子的扩散活动起重要作用，同时在模拟在还观察到了温度低至１００Ｋ时的衍射强度振荡，显示了该成膜初始阶段是一个以原子层为尺度的准逐层生长过程。     

Effect of the cascade energy on defect production in uranium dioxide

The primary damage induced by a displacement cascade in a pure uranium dioxide matrix was investigated using classical molecular dynamics simulations. Cascades were initiated by accelerating a uranium primary knock-on atom (PKA) to a kinetic energy ranging from 1 keV to 80 keV inside a perfect UO₂ lattice at low temperature (300 K and 700 K). There is little effect of temperature in the temperature range studied. Following the cascade event, the damage level, defined as the total number of defects irrespective of whether they form clusters or not, is proportional to the initial kinetic energy of the PKA, in agreement with the literature relating to other materials. The linear dependence of damage upon initial PKA energy results from the formation of subcascades at high energy and constitutes a simple law which can be applied to any material and used in order to extrapolate molecular dynamics results to high energy PKAs. The nature of irradiation induced defects has also been studied as a function of the cascade energy.     

Dynamic binary collision simulation of focused ion beam milling of deep trenches

A new model is presented for the simulation of focused ion beam milling in two-dimensional targets. It combines dynamic Monte Carlo binary collision simulation with cell-based topography simulation, and includes relaxation of cell densities. In the Monte Carlo model advanced algorithms are used for surface treatment, trajectory termination, and collision partner selection. Cell relaxation is performed by minimization of an energy function written in terms of the grid point coordinates, taking the deviation of the cell area from its relaxed value into account, but neglecting viscous forces. Relaxation is limited to areas where nuclear collisions have occurred during cascade simulation. The code is applied to deep trench formation in Si targets by 50 keV Ga focused ion beams. The simulation results indicate the importance of material flow and compare well with experiments.     

Molecular dynamics and Monte-Carlo simulation of sputtering and mixing by ion irradiation

Molecular dynamics (MD) and Monte-Carlo (MC) simulations of low-energy (<500 eV) Ar ion irradiation on Si substrates were performed in order to investigate the mixing and sputtering effects. Both MD and MC simulation show similar results in sputtering yield, depth profile of projectile and mixing of substrate. For these incident energies, the depth of the mixed region is determined by the implant range of incident ions. For example, when the incident energy is 500 eV, the Ar ions reach a depth of 40 Å so that the Si atoms that reside shallower than 40 Å are fully mixed at an ion dose of about 5.0×10¹⁶ atoms/cm². The resolution of secondary ion mass spectrometry (SIMS) was also studied. It was found that the resolution of SIMS depends on the depth of mixing, which depends in turn on the implant range of the probe ions. This is because the mixing of substrate atoms occurs more frequently than sputtering, so that the information about the depth profile in the mixing region is disturbed.     

Effect of impact angle and projectile size on sputtering efficiency of solid benzene investigated by molecular dynamics simulations

Molecular dynamics computer simulations have been used to investigate the effect of the cluster size on the sputtering yield dependence on the impact angle. Ar₃₆₆ and Ar₂₉₅₃ cluster projectiles with 14.75 keV of incident energy are directed at the surface of a solid benzene crystal described by a coarse-grained representation at angles between 0° and 70°. It is observed that the shape of the angular dependence of sputtering efficiency is strongly affected by the cluster size. For the Ar₃₆₆ cluster, the sputtering yield only slightly increases with the impact angle, has a broad maximum around 40°, and decreases at larger angles. For the Ar₂₉₅₃ cluster, the yield strongly increases with the impact angle, has a maximum around 45° followed by a steep decrease at larger angles. For both investigated cluster projectiles the primary energy is deposited so close to the surface so that the sputtering efficiency only weekly benefits from the shift of the deposited energy profile toward the surface which occurs at larger impact angles. In this study, molecular dynamics computer simulations are used to probe the effect of the impact angle on the efficiency of ejection molecules emitted from solid benzene by 14.75 keV Ar₃₆₆ and Ar₂₉₅₃ clusters.     

MD and OKMC simulations of the displacement cascades in nickel

The molecular dynamics(MD) method was used to investigate the displacement cascades with primary knock-on atom(PKA) energies of 2-40 keV at 100 and600 K.The migration energy of defects and their clusters was calculated by nudged elastic band(NEB) method.Object kinetic Monte Carlo(OKMC) was used to simulate the evolution of defects in Ni under annealing.In each annealing stage,the recombination mechanism was discussed and evolution of the defects under different cascade conditions was compared.It was found that the defects generated in high-temperature cascades are more stable than those in the low-temperature cascades.In addition,almost all the defects are annihilated during annealing process at low PKA energy.At PKA energy of 20-40 keV,however,a large number of defects would remain after annealing.     

Promoting effect of ethanol on dewetting transition in the confined region of melittin tetramer

To study the influence of ethanol molecules on the melittin tetramer folding,we investigated the dewetting transition of the melittin tetramer immersed in pure water and 8%aqueous ethanol solution(mass fraction) by the molecular dynamics simulations.We found that the marked dewetting transitions occurred inside a nanoscale channel of the melittin tetramer both in pure water and in aqueous ethanol solution.Also,ethanol molecules promoted this dewetting transition.We attributed this promoting effect to ethanol molecules which prefer to locate at the liquidvapor interface and decrease the liquid-vapor surface energy.The results provide insight into the effect of ethanol on the water dewetting phenomena.