制备高分辨率Si(Li)X射线探测器的进展

Si(Li)半导体探测器对低能X射线具有能量分辨率好、探测效率高、输出脉冲正比于入射光子能量等特点,故已日益引起人们的兴趣。为使Si(Li)探测器有更高的能量分辨率,制造者正努力研究工作在低温的探测器和前置放大器。一般的Si探测器都有一个耗尽层范围,这个耗尽层是对射线灵敏的部分,它的厚度ω可表示为ω=0.3(ρν)~(1/2),这里ρ是使用的P型材料的电阻率,ν,是加到探测器上的反向偏压,由前式可知,用10000Ω/cm的材料,加200V偏压,也只能得到0.4mm厚的耗尽层,这种厚度对测量X射线显然是太薄了,即使是     

Development of a Cherenkov light imaging system for studying the dynamics of radiocesium in plants

High-resolution images of radiocesium (¹³⁷Cs) distribution are required to study cesium kinetics in plants. A Cherenkov light imaging system can visualize fine distributions of radionuclides emitting beta particles using an optical camera. To evaluate the linearity of the system, an imaging test was performed with point sources of ¹³⁷Cs, with a radioactivity of 10–2000 kBq. The results indicated that the system has a good linearity between the image intensity and the radioactivity of ¹³⁷Cs. We developed an imaging system for plants using this system to study radiocesium movement in intact plants. To demonstrate the ability to image radiocesium in a plant, an experiment was performed with an intact soybean plant for four days. The root of an 11-day-old soybean plant was dipped in 20 mL of a culture solution containing ¹³⁷Cs with a radioactivity of 10 MBq without potassium. After one day, the solution was replaced with one with potassium but no ¹³⁷Cs. The soybean plant was in healthy condition in the system, and the high-resolution serial images indicated that ¹³⁷Cs was transported to the shoot and accumulated in the node. Therefore, Cherenkov light imaging is promising for imaging radiocesium in intact plants.     

基于LaBr3(Ce)晶体耦合SiPM阵列的可变角分辨率伽玛相机的设计与研制

编码孔径成像技术由于探测效率高、信噪比高、角分辨率好、成像质量稳定可靠等优点而广泛应用于核安全、核设施的去污及退役的测量、核医学等领域。建立通过改变编码准直器和探测器之间距离进而实现可变角分辨的伽玛成像系统。整个成像系统主要由编码准直器、位置灵敏探测(position sensitive detector, PSD)、数据采集卡以及图像重建系统组成。该成像系统的编码准直器采用修正均匀冗余阵列(modified uniformly redundant array, MURA)编码方式,为了保障对较高能量射线的探测能力,编码准直器的材料采用含钨量90%的钨铜合金,PSD通过LaBr₃(Ce)晶体耦合SiPM阵列组成,重建算法采用的是直接互卷积算法,快速高效。测试结果显示,整个位置灵敏探测器的平均能量分辨率为4.96%(662 keV);该辐射成像系统可以准确地对Am-241、Cs-137、Co-60进行清晰成像,并通过改变编码准直器和探测器之间的距离成功分辨出两个Cs-137点源的位置。     

新型金刚石膜微条气体室X射线探测器

以金刚石膜／硅复合材料作为基板．运用微加工技术在金刚石膜／硅衬底上光刻铬／金微条电极．制成了流气式微条气体室探测器。在室温及101．0kPa下,使用微机多道能谱仪及辅助电子学设备在5．9keV^55FeX射线辐照下测量了微条气体室探测器在不同电压下的能谱响应和脉冲信号。结果表明微条气体室探测器具有较高的信噪比,计数率≥10^3Hz,当混合工作气体Ar：CH4=90：10、漂移电压-1000V、阴极电压-650V、阳极0V时,能量分辨率达12．3％。     

Development of a compact high resolution gamma-ray detector for E-CT applications

A compact gamma-ray detector with good spatial resolution for emission computed tomography (E-CT) applications has been developed. The detector is composed of NaI(Tl) scintillation pixels array and Hamamastu R2486-05 PSPMT. Having a pixel size of 2 mm × 2 mm and an overall dimension of 48.2 mm × 48.2mm × 5 mm, it has 484 pixels in a 22×22 matrix. An average spatial resolution of 2.5mm (FWHM) was achieved. The slope of position linearity is constant within 10% in a range of 40mm. After corrections, the average value of differential non-linearity and absolute non-linearity were 0.16mm and 0.535mm respectively, and a 17% at FWHM of total energy resolution for 241Am was obtained.     

~(238)Pu低能光子源衰变γ能谱识别

利用同轴P型高纯锗探测器,对X荧光分析的~(238)Pu低能光子源进行γ能谱分析,并对~(233)Pa、~(224)Ra、~(212)Pb、~(212)Bi及~(208)Tl的特征γ射线进行分析,确定上述核素的来源。其中,~(233)Pa是生产~(238)Pu的原料237 Np的衰变产物,~(224)Ra、~(212)Pb、~(212)Bi及~(208)Tl均为生产~(238)Pu的副产物~(236)Pu的衰变子核。能量为350、440、844、1 014、1 130、1 266、1 368、1 454keV的γ射线是α粒子轰击源封装材料引起原子核库伦激发或γ射线照射周边环境引起核激发产生。进行效率刻度后,使用γ能谱法计算各放射性核素的活度,并根据放射性平衡计算各放射性核素的质量。通过对~(238)Pu源γ能谱的分析,建立计算放射性同位素活度与质量的方法。     

核电厂运行现场高能γ射线的剂量调查

在核电厂正常运行期间,反应堆冷却剂系统内存在能够发射高能γ射线的¹⁶N等放射性核素。为了初步掌握核电厂运行期间不同区域内高能γ射线的辐射水平,利用NaI(Tl)谱仪在国内某核电站测量了反应堆厂房内的γ能谱,并根据γ测量谱和测量系统的响应函数计算了能量大于3 MeV的γ射线的场所剂量率。结果显示:在15个测量位置中,6个位置的γ测量谱中存在明显的高能成分,其对应的剂量率在1.02～30.14 μSv/h范围内。     

高能X射线CT技术在辐照后核燃料组件检测中的发展及应用

定期检测辐照后核燃料组件对保障反应堆安全运行和开展高燃耗下核燃料组件的性能研究具有重要意义。为了能在不拆卸、不破坏燃料组件的情况下更好地观察燃料组件及其内部燃料棒的缺陷及结构变化等信息,高能X射线计算机断层扫描(X射线CT)技术作为一种有效手段可用于辐照后核燃料组件的检测。日本多年来一直致力于该技术的研究工作,成为世界上唯一一个研制出用于辐照后燃料组件检测的高能、高分辨率X射线CT检测装置且应用于快中子反应堆现场检测的国家。为此,本文梳理日本近几十年来相关研究成果,介绍日本原子能研究开发机构(JAEA)研发的燃料组件高能X射线CT装置结构、工作原理、研究现状及部分应用实例,以期对我国核燃料组件无损检测技术的发展提供参考、借鉴。     

一台便携式伽玛相机的数据采集系统设计

介绍了一套用于便携式小型伽玛相机成像的高性能数据采集系统.为满足其便携式移动方便的要求,该数据采集系统的设计基于通用的USB接口,采用模块化的设计与系统集成.选用多通道数据同时采集的高速USB-ADC卡(DT9836)与LabVIEW软件开发平台,实现了高分辨小型伽玛相机多通道数据的同时采集、处理、图像显示与存储等功能...     

5×1024×10高速核辐射能谱获取系统研制

在磁约束聚变实验装置的物理实验中，为了测量高温等离子体箱射的某特定能量区域的X射线或其他核箱射能谱的时、空分布，需要在托卡马克的板向和环向方向布置多台X射线探测器，每次放电可同时获得数十个能谱，为了不牺牲能谱中的重要信息(如线辐射)．以及能量分辨的需要，要求每个能谱有1024道，每个谱采集的时间分为：40、80、160、240ms，可自由设定，每道容量16位，每次放电可同时获得50个能谱，可扩展到80个能谱。     

Monte-Carlo simulation of pinhole collimator of a small field of view gamma camera for small animal imaging

Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022% and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the wade-off between sensitivity and resolution.     

低纹波微型X射线管高压电源的研制

国内研发的X射线高压电源体积普遍较大,不适合微型X射线管的要求。针对微型X射线管的特点,本文设计了一种低纹波、小体积高压电源,其输出电压在0~-40kV范围内可调。电源的逆变电路采用罗耶谐振电路,并引入UCC2973控制芯片以提高其效率。在电源的升压部分设计了高频变压器、双向倍压整流电路,以进行两级升压。通过电阻分压后取样反馈的方式进行稳压。电路工作在线性状态,无开关噪声。测试结果表明,电源的输出电压纹波低于0.3%、稳定度优于0.12%/10h,可满足微型X射线管的需求。     

Development of precise energy spectrum measurement technique for high-power pulsed X-ray sources for industrial use

It is difficult to obtain an accurate energy spectrum by measurement for X-rays which are produced by linear accelerators because so many photons are emitted within a very short period and the photons have energies in a wide range. In order to solve the problem, we developed a new technique utilizing the Bayesian estimation method combined with attenuation curve measurement using a step-shaped attenuation material. We experimentally confirmed the validity of the presented technique for an X-ray computed tomography (CT) system. By using the accurate energy information of emitted X-rays obtained by the developed technique, the quality of non-destructive inspection images can be expected to be improved for industrial X-ray radiography, X-ray CT and so on, using high-power X-ray sources.     

高氡环境下放射性气溶胶在线监测仪的研制

通过粒度分离采样、真空测量模式、能量甄别法和α/β比值法的氡扣除技术的联合应用,扣除了绝大部分氡、钍及其子体对放射性气溶胶监测的干扰,研制出了高氡环境下放射性气溶胶在线监测仪,并将其在不同氡活度浓度的环境下进行了运行验证,效果良好。该监测仪适用于相关核设施等氡活度浓度较高的场所,为燃料泄漏检查等职业人员的辐射安全提供了重要保障。     

Development of radiation-resistant optical fiber for application to observation and laser spectroscopy under high radiation dose

In the Fukushima Daiichi Nuclear Power Station, it is necessary to survey the locations and conditions of fuel debris inside reactor pressure vessels or primary containment vessels under water and radiation environment in preparation for removing fuel debris. An optical fiber is well known for features such as signal transmission, light weight, superior insulation performance, water resistance and electromagnetic noise resistance. These features allow the optical fiber to simplify the instrumentation systems for in-vessel inspection, as long as provide that the optical fiber can be used under high radiation dose environment. The radiation resistance of an optical fiber was improved by increasing the amount of hydroxyl up to 1000 ppm in pure silica fiber. The improved optical fibers were irradiated with γ-ray up to 1 × 10⁶ Gy using a ⁶⁰Co source. They indicated a large peak around 600 nm and a peak tail from ultraviolet region, but no large absorption in infrared region except a hydroxyl absorption peak of 945 nm. We have confirmed that the optical fiber containing 1000 ppm hydroxyl has enough radiation resistance for radiation-induced transmission losses, and the infrared imaging is effective for observation under high radiation doses.     

Development of a helicon-wave excited plasma facility with high magnetic field for plasma-wall interactions studies

The high magnetic field helicon experiment system is a helicon wave plasma(HWP)source device in a high axial magnetic field(B_0)developed for plasma–wall interactions studies for fusion reactors.This HWP was realized at low pressure(5?×?10~(-3)?-?10 Pa)and a RF(radio frequency,13.56 MHz)power(maximum power of 2 k W)using an internal right helical antenna(5 cm in diameter by 18 cm long)with a maximum B_0of 6300 G.Ar HWP with electron density~10~(18)–10~(20)m~(-3)and electron temperature~4–7 e V was produced at high B_0 of 5100 G,with an RF power of 1500 W.Maximum Ar~+ion flux of 7.8?×?10~(23)m~(-2)s~(-1)with a bright blue core plasma was obtained at a high B_0 of 2700 G and an RF power of 1500 W without bias.Plasma energy and mass spectrometer studies indicate that Ar~+ion-beams of 40.1 eV are formed,which are supersonic(~3.1c_s).The effect of Ar HWP discharge cleaning on the wall conditioning are investigated by using the mass spectrometry.And the consequent plasma parameters will result in favorable wall conditioning with a removal rate of 1.1?×?10~(24)N_2/m~2 h.     

Development of a dimensionless parameter for characterization of dielectric barrier discharge devices with respect to geometrical features

Non-thermal plasma (NTP) devices produce excited and radical species that have higher energy levels than their ground state and are utilized for various applications.There are various types of NTP devices,with dielectric barrier discharge (DBD) reactors being widely used.These DBD devices vary in geometrical configuration and operating parameters,making a comparison of their performance in terms of discharge power characteristics difficult.Therefore,this study proposes a dimensionless parameter that is related to the geometrical features,and is a function of the discharge power with respect to the frequency,voltage,and capacitance of a DBD.The dimensionless parameter,in the form of a ratio of the discharge energy per cycle to the gap capacitive energy,will be useful for engineers and designers to compare the energy characteristics of devices systematically,and could also be used for scaling up DBD devices.From the results in this experiment and from the literature,different DBD devices are categorized into three separate groups according to different levels of the energy ratio.The larger DBD devices have lower energy ratios due to their lower estimated surface discharge areas and capacitive reactance.Therefore,the devices can be categorized according to the energy ratio due to the effects of the geometrical features of the DBD devices,since it affects the surface discharge area and capacitance of the DBD.The DBD devices are also categorized into three separate groups using the Kriegseis factor,but the categorization is different from that of the energy ratio.