核径迹孔有关的介观现象

 20世纪前期形成了以量子力学为代表的研究微观世界的科学体系.人们认识到,原子(～(?))或更小尺度范围的物质运动规律与我们日常观察到的宏观范围的物质运动规律有根本的差别.     

3W1永磁多极Wiggler的辐射特性

给出了北京正负电子对撞机(BEPC)同步辐射新组装的3W1 Wiggler束斑强度分布及光子束流的测量结果,并与理论计算作了比较,两者得出了一致的结果.     

多碱光电阴极层状——铯处理多碱光电阴极的附加厚度

根据多碱光电阴极制备过程中的光谱响应在0．4－0．5μm之间光电流减少这一事实，分析了Cs处理多碱光电极的厚度。结果表明，经第一次Cs处理，4μm处的光电流由6mA／W下降到3．8mA／W，第二次处理又进一步降低到1．6mA／W。其主要原因是Cs处理形成的K2CsSb具有一定厚度，光电子在输运过程中由于厚度增加导致散射几率增加，逸出几率下降，从而使光电发射下降。     

扫描SQUID显微镜及其在物理研究和微电子工程中的应用

扫描ＳＱＵＩＤ显微镜，是９０年代出现的一种新型微结构磁成像仪器，是迄今为止探测微米尺度结构中微弱磁场或微小电充的最灵敏的仪器。它可检测小于１０＾－１０Ｔ的磁场，几个纳安（１０＾－９Ａ）的电流或几百个玻尔磁子的永久磁矩。虽然诞生时间不长，但它无论在基础研究（例如，关于高温超导体波函数对称性的著名三晶超导环实验）还是在应用研究（例如，微电子器件中的捕获磁通问题）都已发挥了重要作用，显示了它在未来科学与     

THOMSON SCATTERING MEASUREMENT OF LASER-HEATED PLASMAS

Experiment on characterizing the laser-heated plasmas using Thomson scattering measurement has been carried out. An incoherent Thomson scattering system with a 90° scattering angle has been established. The influence of the gas density and the pumping laser energy on the temperature of the laser-heated plasma has been examined. The results show that the temperature of the laser-heated plasma increases with the increase of pumping laser energy and the plasma density, which agrees well with the explanation of inverse Bremsstrahlung absorption.     

激光二极管泵浦的Cr:LiSAF二次谐波产生获得可调谐蓝色激光连续输出

以６７９ｎｍ的激光二极管泵浦１ｍｍ厚掺杂摩尔分数为０．０２２Ｃｒ：ＬｉＳＡＦ,用α－切割的１类非临界位相匹配的ＫＮ晶体进行内腔倍频,在吸收功率在２５６ｍＷ时,得到了峰值３．１５ｍＷ,波长为４３１．７ｎｍ的ＴＥＭ００模蓝色激光输出,激光阈值为９６ｍＷ,斜效率为１．９７％,通过改变ＫＮ晶体的温度,实现了波长范围为４２３．４～４４５．５ｎｍ之间的连续可调谐蓝色激光输出。     

高压剪切作用下三水铝石的结构稳定性

利用旋转式金刚石对顶砧压机(RDAC)结合显微激光拉曼光谱和微区X射线衍射,研究了三水铝石(γ-Al(OH)₃)在高压剪切作用下的结构稳定性。常温加压至1.5 GPa,旋转180°后,γ-Al(OH)₃的结构开始转变。初始样品在高波数段的4个羟基伸缩振动峰(3363、3434、3524和3618 cm^-1)相继消失,出现3303和3560 cm^-12个新峰。低波数段拉曼谱强度明显减弱,无非晶态宽峰;Al-O-Al变形振动双峰(568、539 cm^-1)和Al-O伸缩振动肩峰(321和307cm^-1)分别融合为一个振动峰;4个羟基变形振动峰(1052、1018、981和922 cm^-1)仍然可见。继续加压至3.5 GPa,旋转360°后卸至常压,高波数段新出现的两个羟基伸缩振动峰、原Al-O-Al变形振动峰和Al-O伸缩振动峰仍然可见。对比准静水压条件下γ-Al(OH)₃高压相的拉曼谱和相转变压力(约2.7 GPa),认为常温高压剪切作用下γ-Al(OH)₃脱羟基生成了H₂O和H₃O^-₂。卸压样品微区的X射线衍射谱进一步揭示,在高压剪切作用下,γ-Al(OH)₃的(OH)-Al-(OH)配位八面体骨架被破坏,沿c轴方向原子叠加的层间距缩小,对称性增强。这种不同于准静水压实验的结构改变来自腔体内压力的不均匀分布(0.5~4.5 GPa)。高压剪切作用下,三水铝石的结构稳定性研究对查明板块冷俯冲带中含水矿物的稳定性,推演俯冲板片的物理化学性质以及板块俯冲的速率具有重要意义。     

Research progress of Pt and Pt-based cathode electrocatalysts for proton-exchange membrane fuel cells

Proton-exchange membrane fuel cells (PEMFCs) have been widely used commercially to solve the energy crisis and environmental pollution. The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in PEMFCs. Platinum (Pt) catalysts are used to accelerate the ORR kinetics. Pt's scarcity, high cost, and instability in an acidic environment at high potentials seriously hinder the commercialization of PEMFCs. Therefore, studies should explore electrocatalysts with high catalytic activity, enhanced stability, and low-Pt loading. This review briefly introduces the research progress on Pt and Pt-based ORR electrocatalysts for PEMFCs, including anticorrosion catalyst supports, Pt, and Pt-based alloy electrocatalysts. Advanced preparation technology and material characterization of Pt-based ORR electrocatalysts are necessary to improve the performance and corresponding reaction mechanisms.     

Temporal response of laminated graded-bandgap GaAs-based photocathode with distributed Bragg reflection structure: Model and simulation

To describe the dynamic response characteristics of the laminated graded-bandgap GaAs-based photocathode with distributed Bragg reflection structure, a general theoretical temporal response model is deduced by combining the unsteady continuity equation and numerical calculation method. Through the model, the contribution of the distribution Bragg reflection structure and graded-bandgap emission layer to the temporal response are investigated. Meanwhile, the relationships between the temporal response characteristics of the laminated GaAs-based photocathode and different structural parameters are also analyzed, including average electron decay time, emission layer thickness, and incident light wavelength. It is found that the introduction of distribution Bragg reflection (DBR) layer solves the discrepancy between the absorption capability of the emission layer and the temporal response. Moreover, the distributed Bragg reflection layer can improve the time response by optimizing the initial photoelectron distribution. The improvement effect of the DBR layer on the temporal response is enhanced with the emission layer thickness decreasing or the incident light wavelength increasing. These results explain the effect of the DBR layer of the photocathode on the dynamic characteristics, which can offer a new insight into the dynamic research of GaAs-based photocathode.     

用于神光Ⅲ原型装置20 kJ能源系统的研制

在神光Ⅲ原型棒状放大器能源系统中,采用LC串联谐振变换器构成的软开关式恒流充电单元设计了高精度充电机.同时,基于RLC串联谐振电路的临界阻尼特性,设计了脉冲成形单元.分析了氙灯非线性解决办法及内触发点灯方式的可靠性,得出了脉冲氙灯线形等价和触发脉宽影响点灯可靠性的结论.采取计算机远程集中控制的控制策略,使得该系统控制安全高效.设计的20套能源模块完全符合用户要求,说明该方案具有可行性.