基于蒙特卡罗模拟方法,对比分析了圆柱型闪烁体探测器NaI(Tl)、LaBr3(Ce)及锗酸铋(BGO)对γ射线的探测效率,研究了晶体尺寸、入射 γ 射线能量、放射源与探测器间距离、包壳材料厚度对探测效率的影响.在相同条件下,BGO的绝对探测效率、全能峰探测效率及本征探测效率均大于LaBr3(Ce)及NaI(Tl).对于BGO探测器,探测效率与晶体尺寸呈正相关关系;绝对探测效率及全能峰探测效率随γ射线能量的增加呈现先上升后下降趋势,本征探测效率与γ射线能量呈负相关关系;绝对探测效率及全能峰探测效率与放射源与探测器间距离呈负相关关系;包壳材料厚度对本征探测效率几乎无影响,越薄的铝制外壳可达到越好的绝对探测效率及全能峰探测效率.该研究结果能够为闪烁体探测器几何设计、产品研发和无源效率刻度提供一定参考.

三维编织复合材料因其优异的力学性能而得到广泛应用,对其力学性能的研究也取得一些成果.综述了近些年国内外对三维编织复合材料力学性能的研究进展,主要包含试验研究、理论研究,总结了目前研究存在的问题,并对未来的研究趋势做出了展望.

毫米波电子系统在雷达与卫星通信、电子对抗、遥测遥感、航天测控等通信接收系统领域有着广泛的应用.其中,低噪声放大器(Low Noise Amplifier,LNA)作为毫米波通信系统前端接收机的第一级关键电路,在工作带宽内将前端接收到的微弱信号进行放大,并在抑制信号噪声干扰、降低噪声系数,提高接收灵敏度起着至关重要的作用.文章研究设计了一款工作频率范围为32～38 GHz的低噪声放大器,该放大器采用赝同晶型高电子迁移率晶体管(Pseudomorphic High Electron Mobility Transistor,PHEMT)三级级联的电路结构,并采用自偏压供电.在级联的输入端通过匹配网络实现最佳噪声反射系数,在级联的输出端通过匹配电路保证高增益和最大功率传输.末级利用高通滤波器实现增益平坦性,利用电阻网络调节输出驻波比.通过仿真分析表明,该低噪声放大器在32～38 GHz工作频率范围内的噪声系数NF≤2 dB,带内增益G≥20.5 dB,输入与输出回波损耗RL≤9.5 dB.

BackgroundWith the increasing complexity, integration level and data volume of nuclear instrumentation and control system, conventional data buses, such as peripheral component interconnect (PCI) or controller area network (CAN), are difficult to meet the needs of rapid data transmission.PurposeThis study aims to design and implement a Gigabit Ethernet transmission system based on the Xilinx's Zynq-7000 system on chip (SoC) and user datagram protocol (UDP).MethodsFirst of all, the system architecture of UDP Gigabit Ethernet transmission system for nuclear instrumentation and control system was introduced in detail. Then the ModelSim toolkit was employed to verify designed system functions by simulation. Finally, the Gigabit Ethernet transmission system was implemented using ZC706 development board, and tested by experiment.ResultsExperimental results show that the data transmission speed can reach 870 Mbps.ConclusionsThe Gigabit Ethernet transmission system can meet the actual transmission requirements of most nuclear instruments and control system.

文章对NaI(Tl)闪烁体探测器的探测效率使用蒙特卡罗(Monte Carlo)方法进行了模拟计算,在此过程中采用NaI(Tl)闪烁体探测器在实际使用中的封装结构.通过改变反射层的材料以及反射层的厚度(从0.1 cm到0.3 cm),得到不同反射层厚度下的仿真结果,计算出了NaI(Tl)闪烁体探测器的绝对探测效率(Absolute Detection Efficiency,ADE)以及全能峰效率(Full Energy Peak Efficiency,FEPE);根据计算得出的结果,绝对探测效率会随着反射层厚度的增加而增加,同时全能峰效率的变化趋势与绝对探测效率的变化相反.为了平衡绝对探测效率以及全能峰效率,建议选择0.1 cm厚度的反射层.

反应堆控制对象具有非线性和多变量耦合的特点,为了优化控制效果,首要任务是建立较为精确的对象模型.神经网络作为近几年较为前沿的智能算法,对非线性系统的辨识展现了明显的优越性.BP神经网络是一种多层前馈神经网络,文章基于高功率区小范围变负荷的反应堆运行数据,采用BP神经网络进行数据的训练,对训练好的网络进行测试,仿真结果验证了辨识的有效性.

In order to realize the effective acquisition of data required for deep subcritical rod worth calculation, the overall architecture and key modules of deep subcritical rod worth measurement electronics have been researched and designed. The characteristics of the key modules have been tested through reactor test. The results show that the designed deep subcritical rod worth measurement electronics can effectively measure the detector signal transmitted through about 200 m cable. The pulse signal has a stable waveform width and a proper signal-to-noise ratio. The measured high voltage plateau characteristic curve can provide an effective reference for the high voltage selection of the detector. The measured discrimination characteristic curve is stable, from which the neutron component in the detector signal can be effectively obtained.