ETER中子通量监测器的中子学计算

对ITER中子通量监测器（NFM）建立了简化模型并进行了计算分析。利用MCNP程序模拟计算了具有不同慢化剂材料，类型的NFM的探测效率能量响应和时间响应，通过对结果的分析确定了不同NFM上所使用的慢化剂种类及其用量，同时给出了对ITER NFM的初步物理认识。     

ITER水平诊断窗口插件抗震分析与研究

ITER水平诊断窗口插件是位于ITER装置主机赤道面上的重要装置,用于容纳监测等离子体相关诊断参数的设备和仪器。作为一个系统性工程,ITER设计之初就必须考虑地震事件对整体装置的影响。文中运用三维建模软件CATIA对ITER水平诊断窗口插件进行建模,在ANSYS Workbench采用SMS谱和PALEO谱作为反应谱对窗口插件进行响应谱分析,采用根据ITER的各个不同部位在真空室中的位置,来估算出其受到地震影响时的加速度值的方法进行抗震分析,并对分析结果进行了对比。计算结果均表明,ITER水平诊断窗口插件满足其抗震设计的要求,为整个ITER的设计工作提供了工程理论依据。     

ITER 失真空事故下铍灰尘分布的数值研究

采用计算流体动力学方法,通过对ITER 装置的设计结构进行合理简化,建立了ITER 装置的三维计算模型,研究了失真空事故下铍灰尘在ITER 装置内的迁移进程,得到了铍灰尘在ITER 装置内的分布情况。通过分析铍灰尘在不同截面高度、不同时刻的分布特性,得到以下结论：随着高度增加,截面位置上的铍灰尘体积分数呈下降趋势;随着时间推移,截面位置上的铍灰尘体积分数呈上升趋势。     

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采用计算流体动力学方法,通过对ITER装置的设计结构进行合理简化,建立了ITER装置的三维计算模型,研究了失真空事故下铍灰尘在 ITER 装置内的迁移进程,得到了铍灰尘在 ITER 装置内的分布情况。通过分析铍灰尘在不同截面高度、不同时刻的分布特性,得到以下结论：随着高度增加,截面位置上的铍灰尘体积分数呈下降趋势;随着时间推移,截面位置上的铍灰尘体积分数呈上升趋势。     

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为考察ITER真空室中子屏蔽结构组件对选址地法国Cadarache地震加速度频谱的单点响应情况,根据ITER真空室中子屏蔽组件的设计概念和结构特点,建立了组件结构的有限元分析模型。应用有限元分析软件ANSYS对组件进行了结构模态分析,并基于其结果进行了模态叠加。分析发现,组件结构的低阶振型与高阶振型有差异,且结构与低阶频率发生响应,但引起的位移与应力在允许的范围之内。结果表明,装配体结构更能适应结构抗震性的设计要求。仿真计算的结果为组件结构的优化设计和下一步的工程实现提供了可靠的依据。     

ITER导体用铠甲现状综述

ITER超导磁体均采用管内电缆(CICC)结构,铠甲采用奥氏体无磁不锈钢无缝管。针对ITER项目,并通过对国内生产的ITER磁体铠甲性能与ITER性能设计要求值的比较分析,介绍了国内ITER PF、TF等磁体铠甲的生产现状。     

ITER聚变功率关闭系统的一种阀门箱 结构的有限元分析

用ANSYS软件对ITER聚变功率关闭系统(FPSS)的一种阀门箱的结构在ITER各种典型荷载组合下的应力和应变进行了有限元分析，并遵照ASME及ITER标准对分析结果进行了评判。结果表明这种阀门箱结构能够满足ITER的设计要求。     

ITER 中国采购包标准化现状与策略

简要介绍了中国承担设计和制造任务的ITER 计划采购包的构成情况,分析了ITER 采购包采用标准的原则和ITER 中国采购包引用标准的特点,总结了ITER 中国采购包标准化现状。基于当前ITER 中国采购包对标准的需求以及着眼于国内磁约束核聚变长远发展需要,讨论提出了当前ITER 中国采购包的标准化策略建议。     

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简要介绍了中国承担设计和制造任务的ITER计划采购包的构成情况，分析了ITER采购包采用标准的原则和ITER中国采购包引用标准的特点，总结了ITER中国采购包标准化现状。基于当前ITER中国采购包对标准的需求以及着眼于国内磁约束核聚变长远发展需要，讨论提出了当前ITER中国采购包的标准化策略建议。     

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对TF线圈馈线系统做了地震响应分析。利用ANSYS有限元软件对一个TF线圈馈线系统进行了模态分析与响应谱分析,得到了在地震载荷下的峰值响应(应力和位移)。最后,根据 ITER 磁体结构设计标准,对系统的最大Tresca应力进行了评估。结果表明,TF线圈馈线系统满足SC1抗震等级的要求。     

Biosystem response to soft-X-rays irradiation: non-monotonic effects in the relevant biological parameters of yeast cells

Summary Soft-X-rays irradiation of yeast cells allows selective interference with different cellular structures. The monitoring of different physical parameters leads to substantial variations in the response to X-rays showing that monotonicity should not be taken for granted. Also at INFM (Istituto Nazionale di Fisica della Materia).     

Analysis of neutron spectra and fluxes obtained with cold and thermal moderators at IBR-2 reactor: Experimental and computer-modeling studies

The results of experimental and computer-modeling investigations of neutron spectra and fluxes obtained with cold and thermal moderators at the IBR-2 reactor (Joint Institute for Nuclear Research (JINR), Dubna) are presented. These studies are for the YuMO small-angle neutron scattering (SANS) spectrometer (IBR-2 beamline 4). The neutron spectra have been measured for two methane cold moderators for the standard configuration of the SANS instrument. The data from both moderators under different conditions of their operation are compared. The ratio of experimentally determined neutron fluxes of cold and thermal moderators is shown at different wavelengths. Monte Carlo simulations have been carried out to determine the spectra for cold-methane and thermal moderators. The results of calculations of the ratio of neutron fluxes of cold and thermal moderators at different wavelengths are demonstrated. In addition, the absorption of neutrons in the air gaps on the way from the moderator to the investigated sample is presented. SANS with the protein apoferritin was done with both cold methane and a thermal moderator and the data were compared. The prospects for the use of a cold moderator for a SANS spectrometer at IBR-2 are discussed. The advantages of using the YuMO spectrometer with a thermal moderator with respect to the tested cold moderator are shown.     

Development and characterisation of an XeCl excimer laser-generated soft-X-ray plasma source and its applications

Summary A large-aperture, long-pulse XeCl excimer laser has been used to generate a soft-X-ray plasma source. Several laser optical configurations have been employed to optimise X-ray emission, including positive-branch unstable resonators and injection by seeding the gain region of the laser with a small commercial excimer laser, resulting in power densities in the range 10¹²–10¹⁴ W cm⁻². The characteristics of the plasma source for each different laser configuration and for different target materials are investigated. The most suitable source conditions (spectral energy distribution, time duration, etc.) for specific applications are discussed. Supported by the Royal Society, UK. Supported by INFM, Italy.     

Frequency measurements of far infrared laser lines by means of MIM point contact diodes

We present frequency measurements of 85 Far Infrared (FIR) laser lines ranging from 2 748 GHz to 421 GHz. We use the heterodyne technique of mixing FIR laser transitions and microwave radiation on MIM point contact diodes to determine the FIR frequencies.Work supported by Consiglio Nazionale delle Ricerche -Italia and INFM (Consorzio Interuniversitario di Fisica della Materia)     

Physical particularities of nuclear reactors using heavy moderators of neutrons

In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using ²³³U as a fissile nuclide and ²³²Th and ²³¹Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program package for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.     

Positron polarization in chiral media

Summary The positron spin depolarization, relative to the direction of a static magnetic field, was investigated in some chiral media where Ps formation occurs. The results indicate that helical positrons are able to distinguish one enantiomer from the other: the remaining polarizations—just before Ps is formed—differ by about 20% on passing from one enantiomer to the other of the same chiral species. Moreover the existence of a process—strictly connected with chirality and able to hinder any depolarizing process more efficiently than the field itself—has been made evident at low fields. This work was supported by INFM (Consorzio Nazionale di Fisica della Materia).     

Search for spin effect in positron interaction with optically active camphor

Summary The depolarization, relative to the direction of a magnetic field, which accompanies the slowing-down of positrons in the two enantiomers of camphor, down to the positronium formation energy, has been found to be greater (27%) in L-camphor. The measuring method was based on the Ps relative yield, in the magnetic field, in triplet and singlet state. All other annihilation features, as well as the intrinsic properties of Ps once formed, do not display significant differences between the two enantiomers. This work was supported by INFM (Consorzio Nazionale di Fisica della Materia).     

Physical design of target station and neutron instruments for China Spallation Neutron Source

The China Spallation Neutron Source(CSNS)is the first accelerator-based multidiscipline user facility to produce pulsed neutrons by tungsten target under collision of a pulsed proton beam with a beam power of 100 kW at a repetition rate of 25 Hz.In this paper,we focus on the physical design of CSNS target station and neutron instruments.Under optimized design,the flat tungsten target and the compact target-moderator-reflector coupling enhance effective cold and thermal neutron output from moderators.Three wing-type moderators supply four different characteristics of neutrons to 19 beamlines primarily for neutron scattering applications.Layout of neutron instruments are conceptually planned for total 20 beamlines,the configuration and specification have been determined for three day-one neutron instruments.All designs are optimized for the Phase I of 100 kW with a upgradable capacity to 500 kW.     

On the possibility of investigations with very cold neutrons at pulsed sources

The possibility of investigations with very cold neutrons (VCNs) using the example of the IBR-2 pulsed reactor at the JINR FLNP is considered. Possible application areas and specific features of reactor characteristics for these investigations are briefly described. The results of detailed calculations of VCN generation in different cold moderators, VCN transport in neutron guides, and suppressing the contribution of delayed neutrons are presented.     

High flux neutron production from C beams on heavy targets

Spallation neutrons produced from ¹²C ions at 18 and 44 GeV on Cu and Pb targets were studied as well as thermalization in appropriate moderators. The irradiation were performed at the Dubna LHE Synchrophasotron. Results are given for thermal and fast neutrons estimated and compared with different experimental methods.