基于ASIC的GEM自触发电子学系统研制

针对同步辐射衍射探测的需求,设计了一套应用于三层GEM的自触发电子学系统。介绍了此电子学系统的整体架构、系统主要插件的电路设计、FPGA内部逻辑及算法的实现,以及与相应探测器配合的自触发读出方案。最后给出电子学系统初步调试结果。     

小型多参数程控记录仪

针对恶劣环境下信号测试的实际需要,设计了一种通用、灵活的小型多参数程控记录仪。以PIC16F877A单片机和复杂可编程逻辑器件(CPLD)组成的双控制器为核心,实现了对采样频率、触发值、存储长度等参数的可编程设置。USB和SPI双通信接口的设计使系统更具有可扩展性。针对单点测试,可灵活地根据被测信号和应用环境的特殊要求来设定参数并有效记录存储数据。在场测试中,可多点分布并在不同参数下协同工作,以获取尽可能多的场信息。经系统试验,该设计方案切实、可行。     

单光电子谱测试中触发方式对比研究

光电倍增管(PMT)单光电子谱测试中触发方式的对比研究对PMT性能刻度具有很强的指导意义。通过搭建自触发、同步触发、异步触发三套测试系统,对比研究不同触发方式对PMT性能刻度的影响。实验结果表明:自触发只可用于初步性能刻度;而异步触发在信号触发频率小于触发门采样频率时,得到多光电子谱,刻度结果远偏离实际值;同步触发方式能更可靠地刻度出更多更精确的PMT参数,是PMT性能刻度的最佳触发方式。     

多通道同步高速数据采集系统研制

介绍了一个最高采样率为100MHz，采样精度为8bit，基于PCI总线和计算机并口的8通道同步高速数据采集系统的设计，整套系统具有同步误差小、触发方式多样、操作灵活等特点。     

超级神冈中微子的强制触发模块设计

使用强制触发的方法,清华大学高能中心的研究人员首次在日本超级神冈实验的纯水探测介质中观察到了中子俘获寿命曲线.本文讨论强制触发的实现原理和强制触发电子学模块的具体设计,并对实验过程和结果进行了讨论.     

4π BaF2装置的触发系统研究

设计了一套γ全吸收型BaF₂探测装置,用于中子辐射俘获反应截面的在线测量,其中信号测量部分采用了基于高速采集卡的数字化脉冲波形采集技术。并设计了一套触发系统,由触发单元产生的信号作为数据获取系统的外触发控制数据采集,以在数据测量过程中剔除绝大多数本底事件。触发系统采用了符合测量技术,通过多通道、多参数之间的符合测量,实现释放瞬发级联γ射线的中子俘获反应事件的判选和本底的剔除。本文对触发系统的电路设计和实验测试进行了阐述。     

α/β放射性气溶胶的小流量采样快速测量技术研究

针对放射性气溶胶监测仪的便携要求,设计了一套小流量采样快速测量系统和测量方法。采用累积采样累积测量的方式,联合利用能量甄别修正法与α/β比值法去除Rn子体的干扰,实现小流量采样条件下的α/β放射性气溶胶的同时监测。通过对探测下限的分析,表明该方法可满足应急监测的需求,为便携式α/β放射性气溶胶监测仪设计提供了参考。     

塑闪单元条测试系统标定触发电路设计

为记录和分析塑闪阵列探测器(PSD)中塑闪单元条的有效输出信号,设计一款针对PSD塑闪单元条的标定触发电路。该触发电路由时间检出单元和逻辑触发单元组成,使用三路模拟电路实现对三路探测器的精确时间检出。通过现场可编程门阵列(FPGA)进行逻辑符合统计结果,并与上位机通信实现对定时电路的控制,可通过上位机配置阈值和设置符合通道。测试结果表明:该标定触发电路工作性能稳定,计数率高,通道一致性好,能够灵活配置逻辑,可满足使用要求。     

福清核电站余热排出泵漩涡探测报警触发分析

文章介绍了福清核电站余热排出系统漩涡探测装置设置的目的以及报警触发后的动作,及当前设计上为避免泵入口出现漩涡已采取的措施;并结合福清核电机组在满足设计所需采取的措施的前提下触发该报警的现象,详细介绍了该报警触发的经过并结合机组当时的工况分析其原因及漩涡探测触发的机理;分析了该报警触发后所需的响应和可能产生的影响,并最终提出余热排出泵在运行时避免出现漩涡的解决办法。     

一种基于FPGA的高精度单周期TDC设计

设计了一种基于FPGA的高精度TDC,通过延迟链插值和多沿采样等方法,达到与全定制专用集成电路相同的时间精度,实测结果好于9 ps.采用多路选择器阵列和加法器构造的编码器将转换死时间降低到1个时钟周期.设计还使用了自校准的机制,增加了可移植性,可广泛应用于粒子飞行时间探测、核医学影像等领域.     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

Web Services interface of SSRF archive data analysis system

Accelerator database stores various static parameters and real-time data of accelerator. SSRF (Shanghai Synchrotron Radiation Facility) adopts relational database to save the data. We developed a data retrieval system based on XML Web Services for accessing the archive data. It includes a bottom layer interface and an interface applicable for accelerator physics. Client samples exemplifying how to consume the interface are given. The users can browse, retrieve and plot data by the client samples. Also, we give a method to test its stability. The test result and performance are described.     

Investigations on landmine detection by BF3 detector

Experiments were carried out to investigate the possible use of neutron backscattering for the detection of polyethylene (PE) sample buried in the soil. In detection of landmine by neutrons, the neutron detector and its shield play an important role. In this paper, the effects of graphite, heavy water, polyethylene and boric acid moderators on the flux of back scattered neutrons were investigated. We have also experimentally verified the effect of BF3 detector shield and obtained good agreement with theory.     

Gamma radiation levels in the ambient environment of the QNPP Base

Monitoring results of gamma dose rate level in 1992～2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84～113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.     

Preparation and properties of 117m Sn(IV)-TTHMP in in-vitro and in small animals

In this work,TTHMP was synthesized and labelled with 117m Sn.The preparation conditions,stability and lipophilicity of 117m Sn(IV)-TTHMP were investigated.Biodistribution of the complex in rabbits and mice was studied.It was found that the quantity of TTHMP and pH value of the prepararion solution had vital effects on the labeling yield of 117m Sn(IV)-TTHMP.It was also found that 117m Sn(IV)-TTHMP was hydrophilic and stable at room temperature and 37℃ in open air 117m Sn(IV)-TTHMP showed unexpectedly high bone uptake and bone-to-blood ratio in the animals.This made it potentially useful as an reagent for skeletal scintigraphy and radiotherapy of bone tumors.     

Assessment of radioactivity levels in some oil samples from the western desert, Egypt

Distributions of natural gamma-emitting radionuclides were determined in 93 oil samples collected from some petroleum fields in the western desert of Egypt. The radioisotope activities in the area under investigation lay in the range of (21 ± 4) to (38 ± 13) Bq?L-1 for 226Ra, (9 ± 2) to (15 ± 5) Bq?L-1 for 232Th, and (154 ± 28) to (303 ± 54) Bq?L-1 for 40K. The mean values were 27, 12, and 201 Bq?L-1, respectively. Among oils, variations in radionuclide ac- tivities could be on account of differences in TDS, HCO3, and Ba, with high or low pH. In this environment, oil prop- erties differently affected the mobilization of natural radionuclides. The range of 226Ra variation had been compared with available data from other countries. The calculated absorbed dose rate ranged from 22.33 to 32.66 nGy?h-1 in lo- cation (B) and (E) respectively, which was less than the accepted value.