线缆X射线瞬态响应的电路模型计算

建立了同轴电缆和腔体内带保护层导线、裸导线X射线瞬态辐照响应的电路计算模型,该模型考虑了X射线辐照线缆时电子的运动规律及瞬态响应的产生机理,适用于瞬态响应的规律研究和工程预估。结合实例,介绍了计算模型中电流源、电容参数的物理意义及其计算方法,采用该模型计算了同轴屏蔽电缆的X射线瞬态响应,并与数值计算结果进行了比较。结果表明,电容的计算是采用电路模型计算响应的关键,采用衰减法计算的电子射程更适合计算电容。     

直流X射线模拟电缆X射线响应的可行性

本文对电缆X射线辐照响应的机理和模拟方法进行了研究,分析了电缆直流和脉冲X射线辐照响应的异同。建立了带状电缆X射线辐照响应一维计算模型,该模型包含电缆屏蔽层和介质层间隙、介质层瞬态辐射感应电导率等计算模型,模拟了带状电缆直流和脉冲X射线辐照电流响应。模拟结果表明,在X射线注量相同的条件下,电缆直流和方波脉冲X射线响应具有类似的波形特征及相同的间隙电压。因此,在该计算模型描述的电缆X射线辐照响应机制下,可利用直流X射线开展相应的脉冲X射线辐照响应机制模拟。     

屏蔽电缆X射线辐照非线性效应模拟

本文分析了X射线辐照电缆的物理过程,建立了电缆介质层辐射感应电导率(RIC)和间隙效应计算模型,采用有限元方法模拟了电缆X射线辐照非线性效应,给出了诺顿等效电流源(NCD)的非线性响应规律。模拟结果表明,仅考虑RIC效应时,随着X射线注量的增加,NCD幅度存在明显的饱和现象,波形宽度逐渐变窄;仅考虑间隙效应时,NCD幅度近似正比于间隙宽度;当同时考虑两种效应时,间隙效应将会大幅抵消RIC对NCD的影响。因此,在预估核爆环境下屏蔽电缆的X射线辐照响应时,需综合考虑RIC和间隙非线性效应的影响。     

SIP外壳内受X射线激发的电磁干扰环境

本文估算了系统级封装（SIP）外壳内，受脉冲X射线辐照产生的电磁干扰（EMI）环境。首先通过蒙特卡罗数值方法计算了可伐合金及印制电路板（PCB）表面受X射线辐照激发电子的产额和能谱，并基于该计算结果开展了电子自洽运动的数值模拟。利用时域有限差分法（FDTD）和粒子模拟技术（PIC）对电子产生电磁场的过程进行了仿真。计算结果表明，电子的运动使得电子发射面附近的EMI环境最强。此外，从频谱可看出，电磁干扰主要集中在低频部分，且频率取决于X射线的时间参数。通过减小SIP外壳的受辐照面积及高度可降低外壳内的EMI环境强度。     

封闭壳体X射线屏蔽效能测量方法

针对X射线辐照环境中抗辐射加固技术研究的需求,建立了一种适用于电子系统封闭外壳的X射线屏蔽效能测量方法。以X射线机的轫致辐射输出为基础,通过滤波和多个连续谱的组合,实现了接近考核能谱的辐照X射线输出;利用Li F热释光探测器的优势,研究了X射线能量响应标定和屏蔽效能测量的应用方法。重点开展了20–100 ke V硬X射线辐照下封闭腔体屏蔽效能测量的实验研究,测量结果显示,除照射方向上的穿透X射线外,散射X射线对腔体内部剂量场具有显著的贡献。通过实验方法的建立和测量结果的分析,能为X射线抗辐射加固的结构设计和有效性评估提供实验参考。     

N80C196KC20芯片的X射线剂量增强效应

介绍大规模集成电路N80C196KC20单片机芯片在X射线辐射环境下性能的退化及剂量增强效应.用Intel公司的N80C196KC20单片机芯片进行X射线、钴源总剂量辐照试验,测量了电源工作电流ICC,芯片的功能失效表征了它的总剂量响应.芯片在较低的总剂量水平发生功能失效,γ失效总剂量～165 Gy(Si).芯片失效时工作电流发生快速增长.实验测量了N80C196KC20单片机芯片的X射线剂量增强系数,研究了剂量增强效应机理.     

非均匀土壤中埋地电缆HEMP响应研究

为进一步研究埋地电缆在高空核爆电磁脉冲(HEMP)辐照下的电磁瞬态响应,采用了电特性更接近实际情况的双层大地土壤模型,基于传输线方程计算了在HEMP平面波垂直入射下,分层大地土壤中埋地电缆的端接负载响应。分析了电导率分层结构、上层土壤厚度及埋地深度等因素对电缆端接负载感应电流的影响。该研究结果可供EMC设计时参考。     

圆柱形电离室的能响补偿

电离室由于其具有结构简单、使用方便的特点,目前仍被广泛应用于辐射监测领域。用于X、γ射线测量时,必须研究电离室的能量响应,并通过能响补偿使其灵敏度在一定的误差范围内是与入射X、γ射线的能量无关的常数。利用蒙特卡罗方法,模拟计算了圆柱形电离室对X、γ射线的灵敏度和能量响应;并根据计算结果的规律,对圆柱形电离室的能量响应进行了补偿,给出了补偿参数的最优范围。     

pMOS场效应管的X射线和低能强电子束的瞬态电离辐照效应

对电离辐照敏感的厚氧化层ｐＭＯＳ场效应管进行了Ｘ射线和低能强流电子束的瞬态辐照实验；通过对阈电压漂移的跟踪监测，研究了ｐＭＯＳ场效应管的瞬态电离辐照效应。运用辐射感生氧化物、界面缺陷模型并结合ＭＯＳ器件寄生二极管等效电路模型解释了实验结果。     

软X射线辐照LY12铝靶的汽化冲量计算研究

采用数值模拟方法对软X射线辐照LY12铝引起的汽化冲量进行了研究,提出了两种汽化冲量的计算方法,得到了汽化冲量随X射线初始能注量的变化规律.计算结果表明:对于1 keV软X射线,LY12铝的汽化冲量随着能注量的增大而线性增大.计算结果与一些经验公式的计算结果以及实验结果较为吻合.通过对∑miui和∑Pg(t)△t两种方法计算原理的分析和对各计算量的监控表明:两种方法均能较好地计算软X射线辐照材料产生的汽化冲量,但∑Pg(t)△t方法得到的汽化冲量结果更为准确和符合实际.     

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.     

有效探测面积大于1000 cm2的正比计数器测量系统性能测试

为对自制的活性面积高达1 000 cm²的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的²⁴¹Am点源及活性区面积为10 cm×15 cm的大面积²⁴¹Am和⁹⁰Sr-⁹⁰Y源对其进行计量学性能测试。结果表明：计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm²;所得²⁴¹Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;⁹⁰Sr-⁹⁰Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。     

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.     

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.