Variations in backscatter observed in PMMA whole-body dosimetry slab phantoms

Polymethyl methacrylate (PMMA) is a useful material for dosimetry phantoms in many ways including approximate tissue equivalence, stability, accessibility and ease of use. However, recent studies indicate that PMMA may have some unanticipated variation in backscatter from one phantom to another. While the reasons behind the variations have not been identified, it has been demonstrated that the backscatter from one phantom to another may vary by as much as 15%, resulting in a dosemeter response variation of as much as 5%. This unexpected contribution to uncertainty in delivered dose to a dosemeter may be quite large compared to the normally estimated uncertainty, potentially causing problems with calibration and performance testing. This paper includes data supporting the differences in backscatter among phantoms, and results from tests on the phantoms performed in an effort to identify possible causes.     

Measurements of environmental background radiation at location of coal-fired power plants

Environmental radiation monitoring in the vicinity of coal-fired power plants which are used primarily to determine the variability in measured background exposures are presented in this article; this is in order to estimate the contribution due to the plants' operation. Measurements have been done using a multi-element, high sensitive dosemeter system composed of three solid, properly filtered, sintered CaSO4:Dy thermoluminescent detectors, and one low-atomic number, MgB4O7:Dy,Na thermoluminiscencent detector produced at the Vinca Institute. The dosemeters were deployed quarterly 1 m above ground level at locations within 20 km of the power plants. Twenty urban and suburban measured stations were established. Measurements were carried out over one year period, from the beginning of the summer of 1995 to the end of the spring of 1996. The registered annual absorbed dose in air, from all of the 20 stations, vary from 0.91 to 1.46 mGy a(-1). One of the highest values of the annual absorbed dose was measured at the station near to the plant, i.e. at the place the most exposed to the lighter fly ash from the plant stack, as it was expected. The annual absorbed dose registered at the measuring stations that were selected as a control because they were situated practically away from possible influence of the plants were from 0.91 to 0.98 mGy a(-1). The above values of absorbed doses become very important, by concurrence of the circumstances, because they represent the zero background radiation level before the incidence of depleted uranium over former Yougoslav territory in the Kosovo region in the spring of 1999. These measured absorbed dose exposures have to be compared with corresponding absorbed dose rates from the natural sources, such as soil having an exposure of 18-93 nGy h(-1) (average 35 nGy h(-1)) according to the UNSCEAR 2000 Report. This investigation has been primarily done in order to check the impact of coal-fired power plants on the background radiation level in its vicinity. According to the experimental results, influence was confirmed both qualitatively and quantitatively.     

Spectrometry using the PTB neutron multisphere spectrometer (NEMUS) at flight altitudes and at ground level

Bonner sphere measurements are presented for flights at altitudes of up to 12 km and geomagnetic latitudes between 26°N and 86°N and compared with results obtained by several survey meters. As an example of the natural neutron background near sea level, results from a recent longterm measurement campaign performed at the PTB site using an extended spectrometer are presented. The dependence of neutron fluence and ambient dose equivalent on the atmospheric pressure is demonstrated.     

Blast characteristics and TNT equivalence values for some commercial explosives detonated at ground level

We report measurement of the pressure-time profiles produced by the initiation at ground level of four common commercial sector explosives with different detonation velocities. The results indicate that there are no significant differences in the blast waveshapes from the explosives when measured at distances of 25 and 50 m from the initiation point. Analysis of both peak overpressure and positive phase impulse data has yielded values for the TNT Equivalence of the materials at two scaled distances. Our work indicates that the TNT Equivalence values of the materials studied vary with scaled distance and on whether they are evaluated from overpressure or impulse.     

平朔东露天煤矿工业场地地下水位变化影响因素分析

在地下水三维流数值模型研究的基础上,采用参数灵敏度分析的方法,对东露天煤矿工业场地地下水位变化影响因素进行定量分析。结果表明,场地内强风化砂泥岩的渗透性能、填土区大气降水补给能力、盲沟排水能力对工业场地因填土引起的地下水位变化有显著影响。针对这些主要影响因素,进行工业场地各地层渗透系数研究,为完善地面排水系统,控制盲沟质量等提供有力依据,控制工业场地的地下水位上升。     

7Be in ground level air in Daejeon, Korea

(7)Be concentrations in the ground level air in Daejeon, Korea were determined during the period of January 1998 to December 2009 by gamma-ray spectrometric analysis of particulate samples collected on filter paper with a high-volume air sampler. The monthly concentrations of (7)Be in the ground level air were in the range of 1.3-7.7 mBq m(-3) with strong seasonal trends of low values in the summer and high values in the spring and autumn. The annual mean values of (7)Be concentrations showed weak reverse correlation with the annual average sunspot number.     

地震前电磁辐射日变异常观测数据的分析

利用苏家屯地震台的电磁辐射数字化分钟值资料研究了地震前电磁辐射前兆异常现象.发现地震前观测到的电磁辐射超低频电场与磁场出现明显的短期日变异常;超低频电场幅度从120mV逐渐上升为700mV,超低频磁场则由100nT逐渐上升为1100nT.在此异常期间,电磁辐射显示出每天一个准周期的近似方波形态,方波上升和下降时间的规律变化符合"晨昏电势"的概念;信息发展过程明显地周期变化,周期为13.5天,表明晨昏电场是地震孕育过程中的重要现象.发现了以往没有注意到的电离层"异常"现象,拓展了数字地磁观测资料异常提取的应用范围.     

Quality assurance of environmental gamma radiation monitoring in Slovenia

Environmental gamma radiation monitoring established in Slovenia consists of a network of multifunctional gamma monitors (MFMs) based on pairs of Geiger-Müller counters and a network of measuring sites with high-sensitive thermoluminiscence dosemeters. The measuring points are evenly spread across Slovenia, located at the meteorological stations and more densely on additional locations around the Krsko NPP. The MFM network has a 2-fold function with one sensor used for the purpose of early warning system in near surroundings of the NPP and the other, more sensitive, for natural radiation monitoring. The paper summarises activities to establish quality assurance of the environmental gamma radiation measurements in Slovenia, with a critical view of the results in comparison with the international standards and recommendations. While the results of linearity and energy dependence tests were satisfying, on-field intercomparison showed that the inherent signal of one of the monitors (MFM) has to be taken into account in the range of environmental background radiation.     

Investigation of radiation damage to microcapsules in environmental SEM

Abstract

The radiation damage to a specimen in the chamber of electron microscopes has been studied extensively in the past few years. However, for the specific case of specimens with a core/shell structure, such as microcapsules and biological cells, there has been little experimentation devoted to understanding how the radiation may affect their mechanical properties. In the present work, single melamine formaldehyde (MF) microcapsules were imaged using an environmental electron microscope (ESEM) under both dry and wet modes under conditions of different accelerating voltages. The changes in the morphology (shape) were monitored as a function of radiation time. In addition, a newly developed ESEM based nanomanipulation technique was used to measure how the force imposed on single MF microcapsules for a given deformation changed with radiation time, in order to identify a time window within which the radiation damage to the microcapsules may be negligible in order to be able to study the mechanical properties of the particles. Based on the findings, the nanomanipulation technique was applied to measure the force versus displacement for compressing single microcapsules to rupture, including determination of their rupture mode.     

Correlations between switching of conductivity and optical radiation observed in thin graphite-like films

The satisfactory explanation of anomalous electromagnetics in thin graphite-like carbon films till now is absent. The most comprehensible explanation may be the high-temperature superconductivity (HTSC). The pulse widths of spasmodic switching of electrical conductivity measured in this work in the graphite-like nanostructured carbon films, produced by methods of the carbon arc (CA) and chemical vapor deposition (CVD), are 1 and 2 ns correspondingly. Such fast switching completely excludes the thermal mechanism of the process. According to HTSC logic, in the time vicinity close to jump of electroresistance, it is necessary to expect the generation of optical radiation in the infrared (IR) range. This work presents the first results on registration of IR radiation caused by the sharp change of conductivity in thin graphite-like carbon films.     

县级环境监测站内审员在质量体系内部审核中应注意的问题

结合《计量认证/审查认可(验收)评审准则》以及相关文件,阐述县级监测站内部审核中应注意的问题。     

Simple model for the observed plasmon conical radiation interference patterns in a kretschmann configuration

In two previous papers we presented experimental results of measurements with a scanning plasmon optical microscope constructed in the Kretschmann configuration. The angular distribution of the conical radiation from the scanning tip was measured, and the multiple-scattering images of simple surface irregularities were detected. We make a simple model of the multiple-scattering images and compare it with our data, deriving excellent results.     

Scattered gamma radiation utilized for level measurements in gravitational separators

In the petroleum industry, there is a great demand for accurate level measurements and improved process control in gas/oil/water separators. This is necessary to optimize vessel performance, to avoid accidental oil discharge in produced water, and to save cost and environmental hazards from excessive use of chemical additives. It is also important to know how much sand has built up inside the separator. Improved process control has become more important lately due to the increasing demand for more compact systems. This paper presents the work done on the development of a level monitoring system utilizing scattered gamma radiation. Measurements and simulations have been used to find which measurement geometries give the required sensitivity and accuracy. It has been proven that both the sensitivity and the count rate depend strongly on the geometry of the setup and that multiple-scattered radiation dominates the detected response.     

Effects of long-term low-level exposure to radiation as observed in acrylic scintillator: Cause and prevention of radiation disease in uranium calorimeters

The acrylic scintillator which was used for several years as the active medium in the Axial Field Spectrometer uranium calorimeter at the CERN Intersecting Storage Rings was found to be severely damaged. The observed light output has decreased on the average by a factor of 2, and the attenuation length by a factor of 3, causing a severe degradation of the energy resolution of the system for the detection of both electromagnetic and hadronic showers. It could be shown that the effects are due to the radiation induced by uranium decay. The fact that the integrated dose obtained from this process (50 Gy) is 2 orders of magnitude smaller than what was currently believed to be a safe level, strongly suggests that the dose rate is a dominating factor in these radiation damage problems. It could be shown that the radiation resistivity is improved by at least an order of magnitude if contact with oxygen is avoided.     

Internationality at university level

Scientometrics - University level indicators of internationality have been compiled and presented. 18 universities from three countries, Hungary, Israel and Sweden were selected as sample....     

Simulation of inferior mirages observed at the halligen sea

Two unusual forms of inferior mirage are observed and photographed at the Halligen Sea. With heuristic analytic functions for the temperature profiles, numerical integration of the refraction differential equation on a flat earth is performed. The simulation shows that a double inferior mirage can appear if a light wind carries hot air from above dry sandbanks in the mud flats. Horizontal stripes can appear in the mirage image if a water channel crosses the line of sight between the observer and the object.     

Low radiation level detection with room temperature InAs detector

Recently, room temperature or near room temperature InAs detectors are widely used in laser warning receivers, process control monitors, temperature sensors, etc. requiring linear operation over many decades of the sensitivity range. The linearity of zero biased Si, InGaAs and Ge detectors is thoroughly discussed in the literature, contrary to InAs detectors. In an earlier work of the authors it has been demonstrated that applying a bootstrap circuit to a Ge detector – depending on the frequency of the operation – will virtually increase the shunt resistance of the detector by 3–6 decades compared to the detector alone. In the present work, a similar circuitry was applied to a room temperature InAs detector, the differences between the bootstrapped Ge and bootstrapped InAs detector are underlined. It is shown, how the bootstrap circuit channels the photogenerated current to the feedback impedance decreasing with many decades the detectable low level limit of the detector – I/V converter unit. The linearity improvement results are discussed as a function of the chopping frequency, calculated and measured values are compared, the noise sources are analyzed and noise measurement results are presented.     

Validation of the Simpson-finite-difference time domain method for evaluating the electromagnetic field in the vicinity of the lightning channel initiated at ground level

The authors propose a hybrid method, which is a combination between the Simpson method and finitedifference time domain (FDTD) method for evaluating the electromagnetic field radiated by lightning. The proposed method is an alternative approach that takes advantage of this combination to calculate, first, the radiated magnetic field with the Simpson method, and, second based partially on the FDTD method, the electric field. The suitability of this approach is checked through different examples.     

Pit formation observed in a multilayer dielectric coating as a result of simulated space environmental exposure

Certain spaceborne telescope designs require that dielectric-coated lenses be exposed to the energetic electrons and protons associated with the space environment. Test coupons that were exposed to a simulated space environment showed extensive pitting as a result of dielectric breakdown. A typical pit was 50-100 microm at the surface and extended to the substrate material, in which a 10-microm-diameter melt region was found. Pitting was not observed on similar samples that had also been overcoated with a transparent conductive thin film. Measurement of the bidirectional reflectance distribution transfer function showed that pitting caused a fivefold to tenfold increase in the scattering of visible light.