D-T中子穿透铁球伴生γ射线泄漏能谱实验研究

建立了厚度为3,6,11,16,21.8cm的铁球基准装置,用BC-501A谱仪测量了D T中子穿透铁球伴生γ射线泄漏能谱,能量范围为0.5～5MeV。通过康普顿反冲电子法解谱得到γ射线泄漏能谱,通过分析能谱,发现铁球厚度对能谱变化影响有一定的规律。γ射线能谱实验误差为4%～6%。     

Analysis of Intermediate Energy Proton-Induced Spallation Reactions by Improved Quantum Molecular Dynamics Plus Statistical Decay Model

Intermediate energy proton-induced spallation reactions with various targets are studied by the improved quantum molecular dynamics （ImQMD05） model incorporated with the statistical decay model （SDM）.     

Improved Quantum Molecular Dynamics Model and its Application to Fusion Reaction Near Barrier

An improved quantum molecular dynamics model is proposed. By using this model, the properties of ground state of nuclei from 6Li to 208Pb can be described very well with one set of parameters. The fusion reactions for 40Ca 90Zr, 40Ca 96Zr and 48Ca 90Zr at the energy near the barrier are studied by this model. The experimental data of the fusion cross sections for 40Ca 90,96Zr at the energy near the barrier can be reproduced remarkably well without introducing any new parameters. The mechanism     

Single Event Upsets in RAMs Induced by Protons at 4.2 GeV and Protons and Neutrons below 100 MeV

Several different types of random-access-memories (RAMs) have been tested for soft upset susceptibility under a variety of different particle bombardments including thermal neutrons, GeV protons, and protons and neutrons below 100 MeV and with few exceptions found to suffer single event upsets. Devices tested included 4K, 16K and 64K dynamic RAMs and 4K NMOS and 256×4 CMOS static RAMs. Mean upset fluences varied from 106 particles/cm2-upset for 64K dynamic RAMs up to no upsets observed for the 256×4 CMOS RAM. No thermal neutron induced upsets are believed to have occurred. GeV protons, simulating primary cosmic rays, caused upsets at levels of 107 particles/cm2-upset.     

D-T中子穿透铁球伴生γ射线泄漏能谱实验研究

建立了系列厚度为3、6、11、16、21．8cm的铁球基准装置。用BC-501A谱仪测量了D-T中子穿透铁球伴生γ射线泄漏能谱，能量范围为0．5～5MeV。通过能谱分析，观测到铁球厚度对能谱有一定影响。利用MCNP4A程序和t-2、ENDF／B-V、ENDF／B-Ⅵ和FENDL-2等数据库对实验进行了模拟计算，并将计算结果与实验结果进行了比较。γ射线能谱实验误差为4％～6％。     

质子和中子引起的单粒子效应及其等效关系理论模拟

根据器件几何尺寸、掺杂浓度、偏压等因素确定灵敏体积和临界电荷,从而提出单粒子效应的物理模型。考虑了质子和中子在硅中的弹性散射、非弹性散射、两体反应、多体反应以及质子的库仑散射等所有相互作用类型,采用蒙特卡罗方法模拟跟踪入射粒子与核的相互作用以及各种次级带是粒子和反冲核的能量沉积过程。采用Ziegler的拟合公式精确计算质子、a粒子、氚核、反冲核等带电离子的能量沉积。根据模拟结果确定了两种粒子引起的单粒子效应等效系数,并将模拟结果与实验数据进行了对比。     

Giant Monopole Resonance and Symmetry Energy

Nuclear matter incompressibility is discussed by the framework of a fully consistent relativistic random phase monopole compression modes in nuclei in the approximation, based on effective Lagrangians with a mixed isoscalar-isovector nonlinear coupling term. A predicted value of the matter incompressibility coefficient is given by comparison between experimental and calculated energies of the isoscalar giant monopole resonance （ISGMR） in nuclei ^208Pb, ^144Sm, ^116Sn and ^90Zr.     

Application of High Energy Protons in Inertial Confinement Fusion by Using the Fast Ignitor Concept for DT Fusion

A short-laser-pulse driven ion flux is examined as a fast ignitor candidate for inertial confinement fusion. The main mechanism for ion acceleration is charge separation in a plasma due to high-energy electrons driven by the laser inside the target. Another very new branch of fast ignition research is the investigation of the use of laser generated proton beams. In the present paper aims to provide insights into the feasibility of the fast ignition concept with high energy beams of protons generated in laser–plasma interactions. The optimum parameters of an ion beam and laser pulse that are suitable for an ignition spark in a hot precompressed DT fuel are estimated as a rough guide. Also, in this paper we estimate the radius of Deuterium–Tritium (DT) fuel pellet that is equal to the protons range in DT plasma.     

Thermodynamic Characteristics of Dusty Plasma Studied by Using Molecular Dynamics Simulation

Thermodynamic properties of a Debye-Yukawa system of particles are explored by using molecular dynamics simulation in the canonical ensemble. The excess free energy f of the Debye-Yukawa system is calculated by using two different approaches for the liquid phase, and the energy is obtained in a coupling parameter range of 0 ≤ F ≤100 and a wide range of the screening parameter κ. Simulation measurements for excess internal energy and pressure of the system over dimensionless parameters (κ, F) are also presented and compared with previous theoretical and simulated results. A F-expansion-fitting approach for the liquid phase is introduced with the expansion coefficients, which are functions of the screening parameter κ. The fitting coefficients are obtained by directly comparing them with the simulation measurements with a relative deviation of 1% or less. It is shown that the computational results provide a relatively simple method to calculate the excess internal energy and free energy in certain cases, which depend strongly on Г.     

用分子动力学方法研究反应堆堆芯熔化机理

用分子动力学方法数值模拟了反应堆发生堆芯熔化严重事故时,熔化后的熔融金属颗粒从燃料组件上脱落,并落到下管板上,随后继续变形和延展这一过程.通过对此过程物理机理的计算与描述,计算出液滴颗粒的形状及其变化过程,从而揭示、研究堆芯融化严重事故下反应堆堆芯熔化后的力学机理.     

Development of a Double Layered Scintillator for Separating and Detecting Low Energy Protons and Electrons

A scintillator system consisting of a thin (5,000 ? - 15,000 ?) CsI(Tl) layer evaporated onto a plastic scintillator (NE-102) has been developed for the purpose of distinguishing low energy protons from electrons and measuring the energy of each species. Evaporations in a high vacuum (10-8 Torr) produced layers of CsI(Tl) that scintillate with an efficiency comparable to optimally doped bulk material, If the CsI(Tl) layer thickness is 15,000 ?, it stops protons with energies below 170 keV and electrons with energies below 18 keV. Thus, protons with energies between about 25 and 250 keV can be distinguished from electrons with energies above 18 keV by examining the shape of the light pulse generated in the dual scintillator. Results obtained with protons and electron beams will be presented.     

Prediction Method in Numerical Simulation of Dynamics Based on Prompt and Delayed Neutrons in Multiplying Systems

The basic elements of a method of numerical simulation of processes based on prompt and delayed neutrons in multiplying systems are presented. The method is based on predicting the contribution of the instantaneous state of the system to its state at subsequent definite times and summing the predicted contribution as a systematic transition is made to a new moment in time. The key element of the method is determining the initiation functions – the probabilities that a neutron emitted by a source in a prescribed volume of the system initiates a prompt fission neutron in a definite volume of the system sometime after emission. A procedure is proposed for determining the initiation functions; this procedure is based on the first-collision probability method and uses the standard stationary computer codes. The material presented in this paper comprises the basic results of the first stage in the development of the numerical model for full-scale simulation of the dynamics of the subcritical blanket of an experimental accelerator-driven subcritical system under construction at the Institute of Theoretical and Experimental Physics. It is noted that the model being developed can be used to analyze many important processes in other types of multiplying systems.     

用散射中子测量管道油垢厚度的实验与模拟

由~(241)Am-Be中子源、锂玻璃探测器和微机多道谱仪等组成的实验装置,测量了不同石蜡(模拟油垢)厚度的散射中子计数.同时用蒙特卡罗模拟,分别对~(241)Am-Be中子源、~(252)Cf中子源和14MeV中子源,计算得到了相似几何条件下,对应于不同石蜡(模拟油垢)厚度的散射中子计数.在模拟计算中,考虑了锂玻璃探测器的探测效率.对实验和模拟计算的结果进行了比较和讨论.     

Ground-State Properties of Ca Isotopes and Density Dependence of Symmetry Energy

A relativistic mean field model is used to study the ground-state properties of neutron-rich nuclei in Ca isotopes. An additional isoscalar and isovector nonlinear coupling has been introduced in the relativistic mean field model, which could soften the symmetry energy while without changing the bulk properties of symmetric nuclear matter as well as the experimentally known ground state properties of finite nuclei.     

Helium Production in Solid Target and Metallic Window Materials Irradiated with Intermediate and High Energy Protons

The helium isotope formation cross-section has been obtained for iron, tantalum and tungsten irradiated with protons at energies from the reaction threshold up to several GeV. The cross-section evaluation has been performed using the results of model calculations and by the analysis of available experimental data.

The numerical calculations were carried out using the modified ALICE code and the CASCADE/INPE code.     

Numerical Experiments on Oxygen Soft X-Ray Emissions from Low Energy Plasma Focus Using Lee Model

The X-ray emission properties of oxygen plasmas are numerically investigated using corona plasma equilibrium model. The Lee model is here modified to include oxygen in addition to other gases. It is then applied to characterize the Rico Plasma Focus (1 kJ), finding a oxygen soft X-ray yield (Ysxr) of 0.04 mJ in its typical operation. Keeping the bank parameters and operational voltage unchanged but systematically changing other parameters, numerical experiments were performed finding the optimum combination of pressure = 3 Torr, anode length = 1.5 cm and anode radius = 1.29 cm. The optimum Ysxr was 43 mJ. Thus we expect to increase the oxygen Ysxr of PF-1 kJ thousand-fold from its present typical operation; without changing the capacitor bank, merely by changing the electrode configuration and operating pressure. The modified version of the Lee model code is also used to run numerical experiments with oxygen gas, for optimizing the oxygen soft X-ray yield on the new plasma focus device PF-SY2 (2.8 kJ). The static inductance L₀ of the capacitor bank is progressively reduced to assess the effect on pinch current I_pinch. The experiments confirm the I_pinch, limitation effect in plasma focus, where there is an optimum L₀ below which although the peak total current, I_peak, continues to increase progressively with progressively reduced inductance L₀, the I_pinch and consequently the soft X-ray yield, Ysxr, of that plasma focus would not increase, but instead decreases. The obtained results indicate that reducing the present L₀ of the PF-SY2 device will increase the oxygen soft X-ray yield till the maximum value after that the Ysxr will decrease with I_pinch decreasing.