一种用于高能物理实验的时钟相位精确同步方法

现代高能物理实验中,对时钟系统有着精度和稳定性的要求。高速串行通信技术,因其能够在进行数据传输的同时进行时钟数据恢复而得到广泛应用。针对因此带来的恢复时钟相位不确定性,设计了一种基于串并转换技术和FPGA的时钟同步方法,能够为高能物理实验多节点时钟系统提供精确相位同步的时钟。该方法利用FPGA内部硬件资源对恢复时钟进行处理,串并转换芯片自带的状态位和优秀的串并转换能力极大地简化了系统设计,并增强了系统性能。     

基于时钟消抖电路的高精度全局时钟同步设计

基于串行/解串器技术的核电子学时钟同步系统的抖动会逐级累积,为此设计了基于锁相环的时钟抖动消除电路。通过选择合适的环路滤波器带宽,可以将时钟抖动降低到9 ps左右。建立了附加抖动模型以估计时钟分发的最大级数。测试表明,时钟抖动消除电路能够保证全局时钟顺利分发下去,可以在实际工程设计中借鉴使用。     

穆斯堡尔谱仪中的时钟产生器

本文阐述了用于穆斯堡尔谱仪中的时钟产生器的特点和工作原理。对新研制生产的FH1085A型时钟产生器的主要技术性能作了介绍。     

基于FPGA的数字时钟设计

本文介绍一种基于FPGA的数字时钟设计方法：DCM（数字时钟管理器）。DCM使用完全数字反馈系统确保多个时钟同步,使用完全数字延迟线技术可以精确控制时钟的频率和相位。用户可以编程控制时钟任意倍频和分频及任意相位移动,使用非常方便可靠。文章还给出应用设计原理图及逻辑仿真波形图。     

陆上地震勘探数据同步采集与实时传输的设计与实现

针对陆上地震勘探的特点,设计并实现了节点数据同步采集和实时传输系统。一般传感器网络中,传感器节点往往采用本地时钟,并通过软件方法来进行补偿校准,但是由于本地时钟的初始相位不确定性,以及软件校准的局限,往往满足不了高分辨率的地震数据采集要求,故提出了基于时钟恢复和锁相环技术在硬件上实现系统时钟同步的方法,从而实现了节点间数据的同步采集。经过测试,相邻节点的采样时刻最多相差1ns,达到了同步采样的要求。同时系统基于串行/解串技术实现了远距离高速数据的实时传输。     

LHAASO水切伦科夫探测器阵列时钟原型系统

介绍了LHAASO WCDA读出电子学时钟原型系统的设计,分析了该时钟系统的设计原理,介绍了测试方法和测试结果.该原型系统基于精简的White Rabbit Project原理设计,主要包括时钟源插件、时钟发送插件和时钟接收模块3部分.对该原型系统的测试结果表明,时钟接收模块上两时钟通道之间的时钟偏差可以调整到＜80ps,时钟抖动＜40 ps,可满足LHAASO WCDA读出电子学设计需求.     

4πβ(LSC)-γ放射性活度数字符合平台同步系统设计

介绍了为4πβ(LSC)-γ放射性活度国家基准测量数字符合平台(Digital Coincidence Platform,DCP)数据采集提供高精度时钟与同步测试信号源的实现方法。采用了基于PLL+DDS技术的电路设计方案,提供了系统需要的时钟及正弦波测试信号源。设计基于PXI机箱,通过ALTERA公司的IP软核PCI_CORE进行各板卡间的通信。     

两种远距离时钟传输方式的性能比较

主要比较了在KM2A电子探测器原型样机读出电子学前期预研阶段中的两种远距离时钟传输方式的性能,介绍了基于Rocket IO高速串行数据收发模块和DS92LV16芯片的串并转换原理。分别测试了两种时钟传输方式的发送时钟和恢复时钟的相位关系,并对测试结果进行了比较。     

TOF测量系统读出电子学时钟插件设计

介绍了中国科学院近代物理研究所反应显微成像谱仪和重离子加速器冷却储存环内靶实验中,测量粒子飞行时间读出电子学的时钟插件。两个时钟插件分别集成于3UPXI插件和6UPXI插件上,利用高精度的时钟源和时钟扇出芯片为飞行时间读出电子学系统提供高精度的系统时钟,其抖动分别小于11ps(RMS)和12ps(RMS),满足设计要求。     

玻璃固化过程中硫酸盐分相和分解行为研究

为解决含高浓度硫酸盐的高放废液在玻璃固化过程中出现的黄相问题,首先需了解硫在玻璃固化过程中的行为,尤其是硫酸盐如何从玻璃熔体中分相以及硫酸盐的主要分解温度等。本文针对模拟高放废液玻璃熔制过程中硫酸盐的分相及分解行为进行了研究,在此基础上提出了消除黄相的方法,并进行了实验验证。结果表明,硫酸盐的分相发生在玻璃熔制的早期阶段,约900℃,且一旦发生分相,很难再溶入玻璃体。黄相中的硫酸盐从800℃便开始分解,随着温度的升高,分解速度加快。在1 150℃熔制2h后,熔体表面的黄相完全消失,同时熔体中的硫含量不再发生变化。     

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。     

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.     

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.     

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.     

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.     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

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.