激光聚变气体靶核反应速率双峰现象

利用一维数值模拟分析解释了神光Ⅲ原型高中子产额内爆实验中核反应速率的双峰现象。双峰现象的出现是内爆中核反应区能量竞争的结果。在核反应期间反应区离子的增能机制主要是压缩做功,能量耗散机制主要是离子-电子的库仑碰撞。冲击波在DT燃料中的来回反射,使得核反应区的压缩做功出现强弱交替。压缩做功与库仑碰撞能耗的竞争导致反应区离子内能出现上下波动,使得核反应速率出现双峰现象。实验测量的核反应速率峰值时间与数值模拟结果相一致。     

Review of Japanese fusion program and role of inertial fusion

The high compression of 600 times liquid density and the recent fast heating of a compressed core to 1-keV temperature have provided proof-of-principle of the fast ignition concept, and these results have significantly contributed to approve first phase of the Fast Ignition Realization EXperiment (FIREX) project. The goal of FIREX-I is to demonstrate fast heating of a fusion fuel up to the ignition temperature of 5–10 keV. Although the fuel size of FIREX-I is too small to ignite, sufficient heating will provide the scientific viability of ignition-and-burn by increasing the laser energy thereby the fuel size. Based on the result of FIREX-I, the decision of the start of FIREX-II to achieve ignition-and-burn can be made. The FIREX program is under the collaboration of the Institute of Laser Engineering and the National Institute for Fusion Science.     

Critical distance for fusion and fusion barriers of very-heavy-ion collisions

For the fusion barriers of very-heavy-ion collisions we derive a simple analytical formulae which is based on the concept of the critical distance for fusion. The analytical expression reproduces the experimental fusion barriers within a large range of target-projectile combinations.     

聚变反应随时间变化诊断装置辐射转换体设计

聚变反应随时间变化诊断装置是惯性约束聚变(ICF)研究中的一项重要诊断设备, 使用蒙特卡罗程序Geant4研究了基于气体切伦科夫探测器的聚变反应随时间变化诊断装置的时间分辨和辐射转换效率,给出了优化后的辐射转换体材料厚度,以及CO2气室压力与长度。模拟计算表明,优化后的系统时间分辨可达22 ps左右,伽马-切伦科夫光子转换效率可达4.710-3 Cherenkov photons/gamma。     

Polarized fusion

Since more than 50 years it has been discussed to increase the gain of nuclear fusion reactors with the use of polarized fuel. For example, the total cross sections of the fusion reactions d + t → ⁴He + n or ³He + d → ⁴He + p are increased by a factor of about 1.5 if the spins of both incoming particles are aligned. But before polarized fuel can be used for energy production in the different types of reactors, a number of questions must be answered. In this contribution we give an overview on our various activities in this field of research.     

Subcoulomb fusion

The effective barrier at low energies is approximated by a Coulomb and parabolic parts. A closed formula is obtained for the total reaction cross-section at sub-Coulomb energies which agree fairly well with various experimental results. The extrapolation of the results to zero energy leads to a new relation between nucleus-nucleus interaction parameters.     

Antiproton-catalyzed fusion

Because of the potential application to power production, it is important to investigate a wide range of possible means to achieve nuclear fusion, even those initially appearing infeasible. In antiproton-catalyzed fusion, the negative antiproton shields the repulsion between the positively charged nuclei of hydrogen isotopes, allowing a much higher level of penetration through the repulsive Coulomb barrier and greatly enhancing the fusion cross section. With their more compact wave function, the more massive antiprotons offer much more shielding than negative muons. If the antiproton could exist in the ground state with a nucleus for a sufficient time without annihilating, the fusion cross sections are so enhanced at low energies that at room temperature, values up to about 1000 barns (d + t) would be possible. Unfortunately, the cross section for antiproton annihilation with the incoming nucleus is even higher. A model giving an upper bound for the fusion to annihilation cross section ratio for all relevant energies indicates that each antiproton will catalyze no more than about one fusion. Since the energy to make one antiproton greatly exceeds the fusion energy released, this level of catalysis is far from adequate for power production.     

Molecular fusion of fullerenes

New experimental data is reported for the absolute cross sections for the fusion reaction channel in single gas-phase collisions between fullerenes. The experimental data is compared with the results of quantum mechanical and classical molecular dynamics simulations as well as with simple models. Quantum molecular dynamics simulations are in very good quantitative agreement with the experimental data. The overall dynamical behaviour can be well-described qualitatively in the framework of simple models. Received 2 October 2000     

Distribution of fusion barriers

Heavy ion fusion cross sections and compound nucleus average spin values obtained from distribution of fusion barriers are discussed. Various shapes of distribution functions are studied using a truncated Gaussian distribution function (TGD). It is shown that fusion cross section and average spin values are less sensitive to different parametrization of TGD function, whereas the second derivative of the product of energy and fusion cross sections (w.r.t. energy), obtained from the corresponding TGD functions are significantly different depending on the shape of the barrier distribution function. It is also shown byχ ² analysis of fusion cross section data that some systems favour a narrow Gaussian distribution function whereas others, for which the vibrational and rotational collective states are less important, favour a flat barrier distribution. A physical interpretation of the dynamical process that gives rise to different barrier distribution is given in the framework of microscopic coupled channel calculations.     

基于改进自适应加权的多传感器融合监测

针对加注系统多传感器测量数据融合,为满足融合的可靠性与准确性需求,提出了一种改进的自适应加权融合算法。加权融合算法的关键是如何准确判定测量数据权重值,在总结分析当前权重值判定方法优缺点的基础上,将证据理论中的修正证据距离引入测量数据间距离计算,生成融合权重值,完成传感器数据融合。通过一般算例与加注系统典型算例,对所提融合算法进行验证,结果表明算法融合效果较好、鲁棒性强,具有一定的理论意义和较好的工程实用价值。     

Muon-catalyzed fusion theory

Some topics in muon-catalyzed fusion theory are discussed: Resonant formation ofddμ molecules appears to be well understood, with good agreement so far between theory and experiment. The situation for resonantdtμ formation is much less clear, because of the more complicated kinetics, the apparent three-body effect, and the evident need to treat thermalization and molecular formation together to compare theory and experiment. Recent theoretical progress inpdμ fusion by Friar et al. has resolved a serious discrepancy in the Wolfenstein-Gershtein effect, i.e., the increase inpdμ fusion yield with increased deuterium fraction.     

Cold nuclear fusion

Recent accelerator experiments on fusion of various elements have clearly demonstrated that the effective cross-sections of these reactions depend on what material the target particle is placed in. In these experiments, there was a significant increase in the probability of interaction when target nuclei are imbedded in a conducting crystal or are a part of it. These experiments open a new perspective on the problem of so-called cold nuclear fusion.     

Incomplete fusion reactions

A review of incomplete fusion reactions is given. The localization of the entrance chanel angular momentum window is discussed for incident energies lower than 10 MeV per nucleon and is found to depend on the target deformation. With deformed target “peripheral” collisions are observed with ? values in the vicinity of ?_cr for complete fusion, while for spherical targets, the ? window is centered around values lower than 0.5 ?_cr. These properties are discussed on the grounds of available theoretical models. All other properties of the reactions such as cross sections, angular distributions, shape of the energy spectra of light ejectiles are discussed to bring additional informations about the reaction mechanism.