Determination of relevant parameters for the use of electronic dosemeters in pulsed fields of ionising radiation

Active electronic dosemeters using counting techniques are used for radioprotection purposes in pulsed radiation fields in X-ray diagnostics or therapy. The disadvantage of the limited maximum measurable dose rate becomes significant in these radiation fields and leads to some negative effects. In this study, a set of relevant parameters for a dosemeter is described, which can be used to decide whether it is applicable in a given radiation field or not. The determination of these relevant parameters-maximum measurable dose rate in the radiation pulse, dead time of the dosemeter, indication per counting event and measurement cycle time-is specified. The results of the first measurements on the determination of these parameters for an electronic personal dosemeter of the type Thermo Fisher Scientific EPD Mk2 are shown.     

Microdosimetry and radiation quality determinations in radiation protection and radiation therapy

Beams of different radiation qualities may, for equal absorbed dose, lead to important differences in the degree of harm for a specific biological endpoint. In many practical situations absorbed dose is then not a sufficient measure when for instance the same treatment result or risk level is the focus of attention. In radiation protection, the absorbed dose may be different by a factor of 20 between the most and least effective radiation qualities. In radiation therapy the corresponding factor is approximately 3. Two physical quantities related to the charged particle track structure, LET, and lineal energy, y, are used to characterise radiation quality. Their values are dependent on whether focus is on targets in the micrometer range (chromosomes, cell nucleus, etc.) or in the nanometre range (DNA structures). The two quantities, LET, and y, have important differences, which emphasise different characteristics of a track. Applications will be discussed.     

使用辐射力天平的超声治疗换能器的电声特性测量方法研究

论述和规范了工作于200 kHz~10 MHz频率范围内的超声治疗换能器的基本电声特性和参数定义,诠释了它们的物理意义和相互关系,研究并提出了一套基于辐射力和有效面积测量的发射换能器的电声参数的测量方法。对平面活塞型、球面聚焦型和圆柱面聚焦型换能器实施了测量,给出了实测结果。     

宽能平面型HPGe探测器能量刻度及MC模拟

为更好服务于环境辐射监测,通过标准放射点源241Am、133Ba、60Co、137Cs、152Eu对平面型HPGe探测器进行标定,分别获得不同特征能量下的探测效率、半高宽、道址等数据。数据处理后得到能量-道址函数、FWHM能量刻度函数、能量与探测效率关系,同时求得能量分辨率为1.58keV(60Co,1.33MeV)。通过对比发现,利用CT技术建立的MC模型更加可靠、高效。通过修正上、下死层厚度依次分段对模型探测效率进行校正,得到整体探测效率相对误差在5%以内,与实验结果符合较好。     

Circadian clocks optimally adapt to sunlight for reliable synchronization

Circadian oscillation provides selection advantages through synchronization to the daylight cycle. However, a reliable clock must be designed through two conflicting properties: entrainability to synchronize internal time with periodic stimuli such as sunlight, and regularity to oscillate with a precise period. These two aspects do not easily coexist, because better entrainability favours higher sensitivity which may sacrifice regularity. To investigate conditions for satisfying the two properties, we analytically calculated the optimal phase–response curve with a variational method. Our results indicate an existence of a dead zone, i.e. a time period during which input stimuli neither advance nor delay the clock. A dead zone appears only when input stimuli obey the time course of actual solar radiation, but a simple sine curve cannot yield a dead zone. Our calculation demonstrates that every circadian clock with a dead zone is optimally adapted to the daylight cycle.     

Local lifetime control in silicon power diode by ion irradiation: introduction and stability of shallow donors

Enhanced formation of shallow donors (SDs) in hydrogen or helium-irradiated and subsequently annealed float-zone n-type silicon is investigated. Ion energies, irradiation fluences and annealing temperatures were chosen in ranges typically used for local lifetime control in silicon power devices. Introduced radiation defects and SDs were investigated by deep-level transient spectroscopy and C-V profiling. Results show that radiation damage produced by helium ions remarkably enhances formation of thermal donors (TDs) when the annealing temperature exceeds 375degC, i.e. when the majority of vacancy-related recombination centres anneal out. Proton irradiation introduces hydrogen donors (HDs) which form a Gaussian peak at the proton end-of-range. Their concentration linearly increases with proton fluence and changes dramatically during post-irradiation annealing between 100 and 200degC since HD constituents are reacting with radiation damage. Their annealing in this temperature range is influenced by the electric field. If annealing temperature exceeds 400degC, HDs disappear and the excessive shallow doping is caused, as in the case of helium irradiation, by TDs enhanced by radiation damage. Shallow doping introduced by both hydrogen and helium can have a detrimental influence on blocking voltage of power diodes if high irradiation fluences or wrong annealing conditions are chosen.     

Large-area silicon detection in hadronic sampling calorimetry

The usage of a maximum size silicon wafer area was optimized by using a geometry with two trapezoidal detectors, each of 28 cm². In order to enable the use of silicon detectors for hadron calorimeters a mosaic module consisting of 18 trapezoidal detectors was developed and assembled. Laser cutting technique was employed to minimize the dead area of the mosaic. In the performed investigations no physical deterioration was observed.     

双钢板-混凝土组合结构在沉管隧道中的发展与应用

深中通道沉管管节采用钢壳-混凝土组合结构形式,通过向空钢壳浇筑混凝土预制而成。为评估沉管管节施工后的整体变形,建立了热-结构顺序耦合的分析框架,基于ANSYS APDL及UFPs二次开发模块,分别建立了考虑水化度、日照辐射、大气温度变化的精细温度场模型和考虑混凝土硬化及收缩特性的结构分析模型。通过对足尺管节的温度及应变模拟结果与监测数据的对比,验证了有限元模型的可靠性。在此基础上,分析了日照辐射、大气温度变化等对于管节温度场的影响,同时分析了管节的整体变形模式,以及温度效应、混凝土收缩及自重三种因素对管节整体横向、纵向及竖向变形的影响。结果表明：管节施工过程的温度场表现为时变和空间分布的特征,格仓边部温度受外界气温变化和日照辐射的影响存在周期性波动,而格仓中部温度峰值主要受混凝土自身水化放热特性的控制;管节最终表现为顶板横向及纵向内收,竖向下挠,底板横向及竖向变形不显著;太阳辐射对于结构温度场影响较日气温变化更显著,建议在混凝土温度峰值预测中予以考虑,而日气温变化可采用日平均气温值予以简化;温度效应及材料收缩对管节横向及纵向整体变形影响显著,自重因素导致的变形在横向及纵向的比例为44.3%、11.7%,而在竖向所占比例达92.5%,因而温度效应及材料收缩在管节横向及纵向变形分析中不可忽视;该分析方法可适用于大体积混凝土等结构的温度效应的预测和评估。

     

太赫兹阵列探测器响应度校准溯源研究

提出了一种太赫兹阵列探测器响应度校准溯源方法。首先,使用阵列探测器的每一像元对太赫兹辐照场中心进行逐一扫描,识别有效像元、死像元和过热像元,并对有效像元响应值进行归一化处理,获得阵列探测器的相对辐照度响应值。其次,使用中心像元对太赫兹辐照场进行扫描测量,扫描总面积大于太赫兹光斑尺寸,保证太赫兹功率被完整测量,获得中心像元与其他有效像元的太赫兹功率响应值。最后,用标准太赫兹功率计标定高莱功率计,扩展太赫兹功率校准量限,实现微瓦级太赫兹辐射功率测量溯源,用高莱功率计测得的太赫兹辐射源总功率对阵列探测器测得的积分响应值进行校准,得到阵列探测器辐照度响应绝对值。对探测器进行测量校准和不确定度分析,测得辐照度响应度的相对扩展不确定度为Urel=20%(k=2),测量结果可溯源至国家太赫兹辐射功率标准。     

Structural Design and Static Stress Analysis of Dead Pig Vehicle

Nowadays,in our pig field there has no special device to transport those dead pigs. In normal condition,we need some person to carry out those dead pigs from the pig field.But considering the narrow aisle,manual handling is not convenient,on one hand,these measures will increase the labor costs,on the other hand,these measures will increase the labor intensity of workers. In order to carry out those dead pigs from the pig field fast and efficient,to achieve the purpose of health cultivation,in this paper,we designed a dead pig vehicle to handle those dead pigs. The dead pig vehicle consists of chassis,lifting device,driving device,rotating device,power system and control system. The vehicle adopts self-propelled structure,which is equipped with two lead-acid batteries as power. Loading,transportation,unloading and other dead pig handling full operations can finished by only one person. The result of simulation shows that the dead pig vehicle has a good performance and a good stability,it also can satisfy the requirements of the narrow aisle. The results of this research can provide reference for the similar transportation vehicles.     

CNMAN: a Chinese adult male voxel phantom constructed from color photographs of a visible anatomical data set

A voxel phantom of Chinese adult male called CNMAN was constructed from color photographs of the first Chinese visible human data set, for radiation protection purpose. This data set was obtained from a 35-y-old Chinese male cadaver by a medical university in China. The man, 170 cm in height and 65 kg in weight, was dead without any pathological changes. The image size for transversal anatomical photographs of the whole body was 3072 x 2048. After the photographs were semi-automatically segmented, the voxel phantom (CNMAN) with a voxel size of 0.16 mm x 0.16 mm x 1 mm, consisting of 29 tissues or organs was constructed. Combined with the MCNP Monte Carlo transport code, preliminary results for radiation protection dosimetry were obtained based on this Chinese voxel phantom.     

High survival of frozen cells irradiated with gamma radiation

Cell storage in liquid nitrogen (LN) offers the most secure method of cell preservation even if cryopreserved cells are exposed to natural background of ionising radiation (IR). A lot of experiments have demonstrated that IR can induce damages in living cells, but only a little information regarding the response of cryopreserved cells is available. To investigate the effect of IR on frozen and unfrozen cells, peripheral blood mononuclear cells were directly irradiated at room temperature, then immediately frozen, or frozen and then irradiated in LN with different doses of gamma rays. After thawing, cells were incubated and death fraction was evaluated at different time points. Interestingly, the percentages of dead cells induced by IR gradually increased with both dose radiation and incubation time and were significantly lower for cells irradiated at -196°C than those irradiated at room temperature.     

次声发生机理与装置的研究

本文从平面活塞运动的发声机理出发,研究了次声发生机理,建立了次声场的数学模型,并在此基础上,研制了一种频率,幅度均可调的次声发生装置。通过实验验证了理论模型的正确性,并分析了次声的频率,活塞的振幅,活塞的面积及空间点到声源距离与次声的声压级之间的关系。     

储罐探伤爬壁机器人全遍历路径规划方法

储罐探伤爬壁机器人全遍历路径规划要求机器人高效遍历储罐外壁全部无障碍物区域。结合邻接矩阵、路径选择函数,提出一种单元分解算法并应用于爬壁机器人路径规划中。首先,将爬壁机器人的工作环境简化为二维平面,并通过分析漏检面积确定机器人遍历基本路径;接着,建立栅格环境,对每个栅格赋予x_i值以表示其栅格状态;其次,采用矩形分解法将工作环境划分为若干子区域,通过图的深度优先搜索算法和邻接矩阵确定各子区域的衔接顺序;最后,在子区域的遍历和切换过程中,引入方向函数y_i来判断爬壁机器人是否陷入死区,结合x_i值提出路径选择函数f_i以引导爬壁机器人快速逃离死区。在虚拟环境中进行了仿真实验,仿真结果表明,该方法不仅能引导爬壁机器人以高覆盖率和低重复率遍历工作区域,而且能快速地逃离死区。全遍历路径规划的实现拓展了爬壁机器人在检测储罐罐壁中的应用。     

Using a CCD camera for the determination of the target size in radiation thermometry

The objective of this paper is to present the new objective method for the determination of the target size in radiation thermometry using a charge-coupled device (CCD) camera and the custom-made software. The target size is one of the essential components needed for the proper calibration of a radiation thermometer, as well as for everyday measurements. In practice, most of the radiation thermometers have a small black ring engraved on the ocular, and the interior of the ring defines the target area. Usually, manufacturers state how much radiation is gathered from the target area. Typical values stated are from 90% to 99%. The existing method was very subjective. A person determining the target size looked through the radiation thermometer and tried to read the target size of the thermometer from the millimeter grid paper. In our case, three different people in our laboratory, using this existing method, determined different target sizes. The new method uses a predefined mask of known dimensions, printed on millimeter grid paper and positioned in front of the radiation thermometer. Instead of a person looking through the ocular, a CCD camera and the custom-made image processing software are used. This target size can be used as an indication of target size in cases when other information is unavailable or to check manufacturer's data.     

辐射测温区域的界定分析

文章讨论了谱色测温系统研究中,基于测温坐标系的辐射测温区域的界定问题。以线性发射率模型以及改进的单调发射率模型为基础,通过测温坐标系标尺的考察,分析了不同光谱发射率模型下的辐射测温坐标系所限定的辐射测温有效区域的规律特征;以实际应用中特定的谱色测温仪器为例,给出该仪器适用的辐射测温的理论区域,并用黑体实验进行了验证。     

The definition analyses of radiation temperature measurement area

In the research of primary spectrum pyrometry, this paper discusses the definition problem of radiation temperature measurement area based on the measurement coordinates. For the linear spectrum emissivity model and improved monotonic spectrum emissivity model, the characteristics of radiation temperature measurement area restricted by the measurement coordinates is theoretically analyzed, through the investigations of the temperature and emissivity coordinate axes. Choosing the specific primary spectrum pyrometer as an example in applications, the theoretical area of radiation temperature measurement of this pyrometer is given. And it is verified through blackbody experiments. The discussions of this paper will provide the necessary foundation for the theory research development of primary spectrum pyrometry and the realization of technical applications.     

Superheated drop neutron detectors used at the ESRF

The ESRF operates a 6 GeV electron storage ring to produce X-rays. The experimental hall is classified as a free access area in terms of radiation protection. Interlocked radiation monitors guarantee the corresponding dose constraint. Measurements have shown that the radiation field outside the storage ring is dominated by neutrons. Apfel REMbrandt superheated drop detectors have been chosen. In total, 64 monitors are installed around the storage ring, interlocked to the accelerator personnel safety system. Since the radiation fields are highly pulsed, the response of the REMbrandt monitors to pulsed radiation was measured and compared with theoretical predictions. Dose recordings from the bubble detectors are shown, illustrating the good correlation between beam losses and dose rates, as well as showing the correspondence between neutron and photon dose values. Finally, around the beamline hutches, REMbrandt neutron monitors have been used to evaluate the ratio between neutron and photon dose rates.     

一例空分设备主冷爆炸的原因分析

合钢 15 0 0m3 /h空分设备主冷换热器发生爆炸 ,经分析认为是板翅式换热器“死区”有碳氢化合物集聚造成的 ,提出了预防措施     

聚合物辐射裂解分维与其分子链的运动

从分维理论出发，讨论了聚合物在辐射交联反应中裂解度（Ｐ）与辐照剂量（Ｒ）间的关系。发现分维参数与聚合物内聚能密度密度（Ｅｃ）的表征分子链运动的参数分子链横截面积（Ａｐ）之间有一一对应的关系。建议用方程Ａｐ＝（１／Ｄ－０．４４）／０．００９Ｅｃ计算聚合物的Ａｐ值。用本方法计算出的Ａｐ值与文献值较一致。