NaI探测器搜寻γ源定位准直器模拟设计

为尽快搜寻丢失的γ放射源,模拟设计了用NaI探测器确定γ源方位的铅准直定位装置。设计针对铅准直NaI探测器,运用MCNP软件模拟定位γ源。模拟结果表明,设计的铅准直NaI探测器能够识别γ射线的方向,且角度分辨率高,放射源模拟定位的偏差小,在多个放射源形成的辐射场中能对各个放射源进行定位。     

基于反符合测量技术的HPGe γ谱仪系统峰康比影响因素研究

介绍了反康普顿HPGeγ谱仪系统的结构组成和井型反符合工作原理,对系统在有无反符合测量条件、源与环探测器相对距离以及源强对峰康比的影响进行了实验研究.实验结果表明,系统在反符合测量条件下,标尺相对位置为46.5cm,源强较弱的情况时,反符合测量技术对系统具有很好的抑制康普顿坪的作用,系统峰康比可达最佳值.     

ZEMAX模拟中子相衬成像研究

相衬成像是中子成像领域内的前沿技术,它的成像机理基于中子束的波动性.进行中子相衬成像研究,有必要对这一过程进行仿真计算,但目前尚无模拟中子波动行为的程序出现,本文探讨了利用光学仿真软件ZEMAX对热中子相衬成像过程进行模拟的可行性,介绍了具体的模拟过程和结果,研究了不同的物源距离、物屏距离、点中子源尺寸以及样品尺寸对最终成像结果的影响.仿真结果和理论较为接近,这表明使用该软件模拟中子相衬成像是具有一定的可行性的.     

MURA编码板γ相机探测器模拟研究

用Geant4软件对γ相机探测器的成像原理进行模拟,γ相机探测器主要由准直器和探测单元构成,模拟得到放射源的响应矩阵,通过精细采样算法和δ解码算法进行图像重建。分别模拟了不同形态放射源在不同位置、不同距离、不同角度的成像情况,研究了编码板的偏移和尺寸变化对成像的影响。     

一个用于多重示踪技术的康普顿成像装置

提出了一个由位置灵敏高纯锗探测器组成、用于多重示踪技术的康普顿成像装置.简要介绍了康普顿成像系统的工作原理以及影响其空间分辨率的各种因素.用蒙特卡洛方法模拟了所提出的康普顿成像装置对处于不同位置、发射不同能量γ射线的点源可达到的效率和空间分辨率.用现有的2个多单元高纯锗探测器进行了三个点源成像实验,证明所提出的康普顿成像装置适用于多重示踪技术.     

强γ射线辐射场束流特性诊断

针对校准实验室内强γ射线辐射场束流应用及特性诊断需要,本文建立了辐射场束流特性模拟方法,设计了大面积快响应闪烁体与高速CCD相机组成的束流诊断系统。通过理论模拟及实验测量,在亚毫米位置分辨指标下,实现了对该辐射场内不同距离的束流均匀性、发散角、束流中轴线及快门渡越时间测量。     

基于三NaI(Tl)晶体探测器的放射源定位研究

设计了一种三NaI(Tl)晶体组成的γ射线源定位探测器系统,并通过模拟仿真及实验研究了三NaI(Tl)晶体探测器在137Cs辐射场中全能峰占比计数随距离及入射粒子方向变化的关系。结果表明:在远距离探测情况下,采用全能峰占比法可以有效消除源与探测器间距对角度分辨的影响。对于探测距离约为2.58 m的1.36×106Bq的137Cs源,测量的最大角度偏差≤1.72°,定位位置相对偏差为3.71%。     

NaI(Tl)闪烁探测器对铯源响应的蒙特卡罗模拟

对NaI(Tl)探测器的γ能谱进行了MC模拟,模拟研究了不同源-探距、不同能量分辨率、不同模拟时间和平面源分布等条件下的137Cs γ能谱.137Cs点源的模拟谱与实测谱的对比表明两者基本相符.     

一个用于多重示踪技术的康普顿成像装置

提出了一个由位置灵敏度高纯锗探测器组成、用于多重示踪技术的康普顿成像装置。简要介绍了康普顿成像系统的工作原理以及影响其空间分辨率的各种因素。用蒙特卡洛方法模拟了所提出的康普顿成像装置对处于不同位置、发射不同能量γ射线的点源可达到的效率和空间分辨率。用现有的2个多单元高纯锗探测器进行了三个点源成像实验,证明所提出的康普顿成像装置适用于多重示踪技术。     

快中子成像空间分辨率部分影响因素的模拟研究

采用蒙特卡罗方法对中子成像系统空间分辨率产生重要影响的三个参数(入射中子能量、样品靶与源的距离和探测器与样品靶的距离)进行了模拟研究。利用Geant4模拟计算得到了快中子照射下,调制传递函数随上述参数的变化曲线,这三个参数的选择对成像性能的优化有着很大的指导意义。同时,通过模拟还分析了利用铅隔离层抑制串扰在中子成像中的可行性。研究结果表明,选择合适的铅层厚度在一定程度上提高图像质量,这些结果可为实际工作中的参数选择提供参考。     

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.