基于STM32F407的高压输电线电磁检测系统设计

针对输电线的结构特点,采用涡流检测与漏磁检测相结合的电磁检测方法,设计了一套以高速ARM微控制器STM32F407VG为控制核心器件的高压输电线电磁检测系统。介绍了系统采用直接数字频率合成DDS技术的涡流激励信号产生模块、采用锁相放大技术的涡流信号提取模块、采用差动测量技术的漏磁检测模块、A/D模数转换模块等。上位机程序采用LabVIEW虚拟仪器设计,并通过USB总线与系统进行实时通信。整个系统具有实时性强、易于集成和重构的特点。     

非稀土掺杂协同核壳包裹对氟化物纳米晶上转换发光性能的增强

为提高上转换纳米晶的发光效率,提出协同增强的策略,将核壳包裹和非稀土离子掺杂两种方式进行有效的结合,使上转换纳米晶的发光效率实现"1+12"的增强效果。以Na Gd F_4作为基质材料,Yb~(3+)和Er~(3+)分别作为敏化离子和发光离子,以Li~+离子和Na Gd F_4作为非稀土掺杂离子和包裹壳层来构建核/壳纳米结构,研究两种增强方式的协同作用对Na Gd F4∶Yb~(3+)/Er~(3+)纳米晶的上转换发光性能的影响。结果表明,Li+离子掺杂与包裹Na Gd F4壳层共同作用使得β-Na Gd F4∶Yb~(3+)/Er~(3+)纳米晶的上转换发光增强了39倍,明显优于单一方式的增强效果。通过一系列的优化实验结果发现,Li+离子的最佳掺杂摩尔分数为4%。基于以上实验结果,给出了非稀土离子掺杂核壳纳米晶协同增强上转换发光效率的机理。     

基于成像板-X射线条纹相机的精密耦合技术

为实现惯性约束聚变(ICF)实验中同时获取靶点的X射线1维动态和2维静态积分图像,提出了一种全新的X射线图像采集方法。结合成像板与X射线条纹相机的工作特性,通过在阴极狭缝前精密耦合成像板,实现X射线图像到达狭缝的同时采集其外围区域的静态积分图像。该方法具有对靶点X射线图像的1维动态与2维静态图像对比分析、成像系统像面位置精密空间定位的功能。利用该方法在神光Ⅱ装置上实现搭载Kirkpatrick-Baez(KB)显微镜获得内爆靶球压缩流线图,并应用于流体不稳定性实验中。     

Experimental study of a THGEM detector with mini-rims

The gas gain and energy resolution of single and double THGEM detectors (5 cm×5 cm effective area) with mini-rims (rim less than 10 μm) were studied. The maximum gain was found to reach 5×10³ and 2×10⁵ for single and double THGEMs respectively, while the energy resolution for 5.9 keV X-rays varied from 18% to 28% for both single and double THGEM detectors of different hole sizes and thicknesses. Different combinations were also investigated of noble gases (argon, neon) mixed with a quantity of other gases (isobutane, methane) at atmospheric pressure.     

干灰化法前处理测定茶叶中铅的影响因素

研究了用干灰化法处理茶叶样品时测定铅含量的各种因素的影响,对测定介质、灰化温度、灰化时间、溶剂的选择进行了优化,对基体影响的消除进行了探讨.     

热丝化学气相沉积金刚石薄膜空间场的数值分析

由于热丝化学气相沉积(HFCVD)金刚石薄膜的反应气体利用率较低，生长速率慢，生长不均匀，从而限制了金刚石薄膜的大规模应用。因此，人们从实验和理论方面研究其生长工艺。实验能反映热丝化学气相沉积金刚石薄膜的真实情况，但实验受到许多因素的影响和制约而不能获得较全面信息，数值计算能弥补实验的不足。     

Performance of MPPC at low temperature

The performance of a MultiPixel Photon Counter (MPPC) from room to liquid nitrogen temperatures were studied. The gain, the noise rate and bias voltage of the MPPC as a function of temperature were obtained. The experimental results show that the MPPC can work at low temperatures. At nearly liquid nitrogen temperatures, the gain of the MPPC drops obviously to 35% and the bias voltage drops about 9 V compared with that at room temperature. The thermal noise rate from 10⁶ Hz/mm at room temperature drops abruptly to 0 Hz/mm at -100 ℃. The optimized operation point can be acquired by the experiment.     

Tl-2212本征约瑟夫森结型负阻器件及负阻放大器

我们利用Tl—2212超导薄膜制作出了的本征约瑟夫森结型负阻器件．对于4μm长3μm宽的微桥型负阻器件，峰值电压为0．09V，峰值电流为1．44mA．谷值电压为0．75V，谷值电流为1．05mA，线性区间内负阻阻值约为-1400Ω利用这种器件．制作了简单的负阻并联式电流放大器．实验证明它确实对信号具有电流放大作用，放大倍数可以通过改变负载电阻的大小来改变．     

Luminosity monitoring and calibration of BLM

The BEPCⅡ Luminosity Monitor (BLM) monitors relative luminosity per bunch. The counting rates of gamma photons, which are proportional to the luminosities from the BLM at the center of mass system energy of the ψ(3770) resonance, are obtained with a statistical error of 0.01% and a systematic error of 4.1%. Absolute luminosities are also determined by the BESⅢ End-cap Electro-Magnetic Calorimeter (EEMC) using Bhabha events with a statistical error of 2.3% and a systematic error of 3.5%. The calibration constant between the luminosities obtained with the EEMC and the counting rates of the BLM are found to be 0.84±0.03 (×10²⁶ cm^-2·count^-1). With the calibration constant, the counting rates of the BLM can be scaled up to absolute luminosities.     

神光Ⅲ主机通用诊断搭载平台的研制北大核心CSCD

神光Ⅲ主机通用诊断搭载平台提供各种诊断系统送进和收回的搭载功能,便于诊断系统的拆装和维护保养,同时提供精确的径向、指向瞄准能力,能将诊断系统送至靶室内指定位置,并且能在不破坏靶室真空的状态下安装、调试和维护诊断系统。将通用诊断搭载平台安装在神光Ⅲ原型装置上进行精度检测,得到其真空状态下的径向、X和Y方向指向定位精度分别为36,13,8μm,全行程的径向复位精度、X和Y方向指向复位精度分别达到20,30,12μm。搭载分幅相机诊断包进行激光打靶考核,实验结果表明:其指向瞄准精度、真空性能、接口等均满足使用要求,并具备了对抗强电磁干扰与辐射的能力。