球形托卡马克聚变嬗变堆中子学设计

基于对球形托卡马克ST聚变堆的研究,提出了ST聚变嬗变堆的设计概念。对堆芯参数作了初步选择,确定了一组适合于嬗变包层的堆芯参数供中子学计算和结构设计参考,给出了在以嬗变次锕系元素（MA）核废物为目标的一维中子学计算结果。     

次临界能源堆物理设计进展

聚变-裂变混合能源堆包括聚变中子源和次临界能源堆,主要目标是生产电能。回顾了国内外混合堆的发展历史,给出混合能源堆设计的边界条件和约束条件,说明次临界能源堆以铀锆合金为燃料、水为冷却剂的设计思想。利用输运燃耗耦合程序MCORGS计算了混合能源的燃耗,给出了中子有效增殖因数、能量放大倍数和氚增殖比等物理量随时间的变化。通过分析能谱和重要核素随燃耗时间的变化,说明混合能源堆与核燃料增殖、核废料嬗变混合堆的不同特点。论述了混合堆的热工设计并进行了安全分析。对于燃耗数值模拟程序,通过多家对算,保证其计算结果的可信性。针对次临界能源堆的特点,利用贫铀球壳建立了贫铀聚乙烯装置和贫铀LiH装置,并且专门设计加工了天然铀装置,开展铀裂变率、造钚率、产氚率等中子学积分实验,验证了数值模拟的可靠性。     

聚变中子学的蒙特卡罗PVM并行模拟在ITER中子诊断设计中的应用

聚变能源很可能是人类文明得以维持发展的新型能源。未来的氘氚聚变堆的结构和工程设计很大程度上依赖于以聚变中子学为基础的计算。在过去的十余年中，很多的核数据库如FENDL和JENDL的检验工作围绕ITER设计而展开。聚变中子学计算包括中子和光子的输运计算。其计算目标是提供反应率和能谱等重要的信息。一维或二维的聚变中子学解析计算能提供一定精度的结果和高效率的优化设计，但对于一个三维的聚变托卡马克反应堆来说，只有蒙特卡罗方法能提供较精确的数值模拟结果。MCNP程序是由LANL实验室发展的用于中子和光子的蒙特卡罗计算的大型程序。PVM的并行计算环境能提高为MCNP程序的运行执行效率。     

ST嬗变堆中心柱的中子学及中子辐照效应研究

基于先进核数据库ENDF/B-VI和计算机程序对ST嬗变堆中心柱的中子学及辐照损伤的二维分析计算结果，分别对中心柱导体因中子辐照影响而引起电阻率、电阻、电流和欧姆电阻功率等的沿径向不均匀分布，以及辐照损伤对中心柱热工水力问题及更换寿命的影响进行了分析和计算。结果表明，中子辐照直接改变了中心柱导体材料的电阻率分布。热工-水力学分析和计算表明，电流不均匀分布可显著地延长中心柱的使用寿命，并估算出ST嬗变堆中心柱设计的更换寿命大约8年。     

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基于中国ITER氦冷固态增殖剂试验包层(CHHCSBTBM)3×3模块化结构设计,借助一维中子输运计算程序ONEDANT和二维中子输运计算程序TWODANT,对ITER实验包层模块(TBM)设计的中子学问题进行计算。计算出产氚增殖比以及不同材料区的功率密度、中子通量分布和产氚增殖率,并对计算结果进行分析比较。     

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根据HCSB-DEMO堆的设计要求,对不同尺寸的聚变堆能产生的聚变功率、中子壁负载和等离子体燃烧时间等进行计算与分析,给出了符合设计要求的堆芯参数。在所选定的堆芯参数条件下进行了零维功率平衡计算分析,给出了3组HCSB-DEMO堆的等离子体初步设计参数。     

聚变裂变混合堆设计中的中子学问题

本文简要叙述了聚变裂变混合堆包层设计所涉及的中子γ光子耦合输运方程、核子数密度方程及有关计算机程序系统；介绍用于聚变堆设计的核数据工作现状及未来工作重点。     

ITER试验包层模块的中子学分析与设计

ITER试验包层模块(TBM)的中子学的设计和计算结果为TBM的其它大多数系统设计提供重要的数据依据。本文首先应用TRANSX程序完成基于FENDL2.0新库制作,以及中子输运程序和数据库的基准检验;然后应用二维中子输运程序TWODANT,计算和分析了中国氦冷Li₄SiO₄固体氚增殖剂的试验包层模块的功率密度分布、增殖区产氚特性、结构材料的中子辐照特性、结构材料和增殖材料的产氢和产氦等特性,并给出一个经合理优化的 TBM中子学初步设计结果。     

聚变裂变混合堆处理高放超铀废物的研究

提出一个燃烧高放超铀废物的思路,即在外部聚变中子源驱动下,把燃烧超铀锕系元素和钍铀燃料循环相结合.并且设计相应的一维模型,使用开发的燃耗计算程序ONESN_BURN和新制作的数据库对模型进行计算和分析.通过计算,得到锕系元素的放射性,生物潜在危害因子,高放超铀锕系废物的密度和非常深的燃耗深度等.比较聚变裂变混合堆与传统的热堆,发现中子能谱越硬,对燃烧超铀锕系元素越有效.     

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用蒙特卡洛中子输运程序(MCNPX)对中国聚变工程实验CFETR超导磁体进行中子学输运计算,利用欧洲活化计算程序FISPACT对其进行活化计算分析,针对计算结果重点分析了磁体系统的中子学剂量分布以及活化情况.计算结果表明,中子能量通量最大处出现在聚变堆内侧线圈处,为3.97×1014 MeV·m–2,在该条件下超导线圈可以满足设计要求.停机后磁体组件的活度为3.33×1010Bq·kg–1,停机10年后下降2个数量级达到6.14×108Bq·kg–1.研究结果验证了所使用的CFETR 3维模型满足初步设计条件.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.