加速器质谱学中鉴别重离子的Bragg曲线谱学法的建立

超灵敏AMS技术中遇到的最大测量技术难题是消除来自样品中的同量异位素干扰成分。在AMS测量中,需使用多种高分辨的探测系统。为此,我们设计制造了一台Bragg探测器。Bragg探测器在一个大的能量和原子序数范围内有较好的能量和电荷分辨。该探测器是一全阻止型气体电离室,主要包括     

Bragg探测器在AMS测量中的应用

为提高Bragg探测器的总能量和Bragg峰的分辨等性能,对1台Bragg探测器进行改进,并利用其测量³⁶Cl、⁴¹Ca、⁷⁹Se系列标准样品,有效排除了相应同量异位素的干扰,为进一步提高AMS测量这些中重核的灵敏度提供有效试验手段。     

加速器质谱(AMS)测量中的粒子鉴别探测器

描述了中国原子能科学研究院AMS测量中使用的飞行时间探测器、多阳极电离室、Bragg探测器、入射离子X射线探测器以及充气飞行时间探测器。通过它们可以获得粒子的飞行时间、部分能量和总能量,从而达到粒子鉴别的目的。介绍了采用这些探测器在HI—13串列AMS系统上做的相关工作以及取得成果。     

一种新型气体探测器的研制

加速器质谱(accelerator mass spectrometry,AMS)技术因探测对象不同,探测器也应根据需要进行选择。为建立低能量重离子加速器质谱测量技术,本文设计制作一台新型气体探测器并调试应用。该探测器采用厚度50 nm,膜面积8 mm×8 mm的氮化硅膜作为入射窗。采用5.48 MeV的241Am源的α粒子对探测器进行调试,调试后将该探测器安装于中国原子能科学研究院的300 kV小型AMS系统上进行129I粒子测量。经模拟计算以及对探测器的调试、应用,证明该探测器具有较高的能量分辨率,可以很好的实现不同粒子的鉴别,同时测量灵敏度可达到10^-13国际水平,满足低能量重离子的测量要求。     

Design of Cooling-Water System for Bi-Energy Linactron

有效地鉴别同量异位素是实现AMS技术的高灵敏、高精度测量的关键。Bragg曲线探测器具有相对较高的能量分辨本领，因此，利用Bragg线探测器在AMS测量中进行同量异位素的鉴别将提高AMS测量中对中重核素同量异位素的鉴别能力，为开展AMS长寿命中重核测量提供重要技术手段。本工作对电子信号的获取方式，工作气压，阴极网和流气速度等重新进行了系统测试与改进。     

一台用于重离子鉴别的Bragg曲线谱仪

本文介绍制作的一台用于重离子鉴别的Bragg曲线谱仪。它是一种电场平行于入射粒子方向的全阻止型电离室。其性能用ThC-C’α源和~(252)Cf源进行了测试。对8.785MeV α粒子(ThC’源)能量分辨好于1％,电荷分辨Z/ΔZ=50。     

一台用于重核素测量的能量-飞行时间探测系统

研制了一台用于重核素测量的能量-飞行时间探测系统.探测系统由飞行时间探测器和金硅面垒型能量探测器组成,金硅面垒型探测器兼做飞行时间探测器的停止探测器.用该探测系统在中国原子能科学研究院串列加速器质谱装置上对182Hf9+离子的能量-飞行时间双维谱进行了测量.该探测系统对77.4 MeV182Hf9+离子的能量分辨率为3.8％,飞行时间分辨为0.8ns.     

基于能量-速度关联技术的裂变产物质量分布测量方法研究

采用能量E-速度v关联技术测量裂变产物碎片的动能和飞行速度能精确测定裂变产物核的质量。本工作主要研究能量-速度关联技术的可行性并解决相关关键技术。实验测量系统由飞行时间测量单元、能量探测器和真空靶室系统组成。实验中用1对微通道板探测器测量粒子飞行时间来确定粒子速度,金硅面垒探测器测量粒子能量。对于~(241) Am放射源5.48 MeVα粒子,飞行时间测量系统时间分辨(FWHM)为186ps,金硅面垒探测器能量分辨(FWHM)为44keV。实验完成了~(252) Cf自发裂变源产物质量分布试测量。初步实验结果显示,裂变产物质量分布在110amu(amu为原子质量单位)的位置时,其质量分辨为1.6amu。     

BaF2探测器测量α粒子的时间分辨随温度变化研究

本工作对用于测量α粒子的BaF2探测器的时间分辨随温度变化情况进行了实验研究.实验选用退激Y射线能量较高的237Npα源,利用α粒子与退激Y射线的时间关联性得到时间谱,在不改变任何条件的情况下对BaF:晶体加热,加热到设定温度后保持恒温,在BaF:晶体达到热平衡后开始测量时间谱,由该时间谱上读出的半高宽与标准偏差的线性关系得出α粒子的时间分辨随温度变化的情况.测量结果显示,时间分辨随温度变化在目前实验条件下较为明显,这为未来快时间分辨α粒子探测器的选择和优化使用提供了依据.     

轻重离子焦面探测器系统

经改进后的轻重离子焦面探测器系统（长５００ｍｍ）已通过束流检验并用于核物理实验中。在串列加速器上，以６６ＭｅＶ＾１２Ｃ束流，测得该系统的位置分辨为１．３ｍｍ；△３探测器的能量分辨约为６％；剩余能量Ｅ探测器的能量分辨约为７％；总能量分辨约为３．４％。另外还进行了粒子鉴别试验。     

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.     

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.