Calculation of relative full-energy peak efficiencies of well-type detectors

A mathematical expression to calculate the full-energy peak efficiency of HPGe well-type detectors has been derived in an integral form. The attenuation of photons by the source itself (self-absorption), the source container and the detector end cap materials is also included. The calculated values of the efficiency are found to be in good agreement with the published experimental data.     

Integration of design systems for energy related applications

An EPSRC funded Engineering Design Centre (EDC) has been established at The Queen's University of Belfast to develop integrated design software for energy related applications. Software is being developed for the design of two-stroke engines, power station controllers and wave power stations. These ‘real’ design problems are highly complex with a large number of interrelated variables resulting in a wide range of design permutations. Although at an early state of application, the advantages of using object orientated design/programming methodologies is being demonstrated in the development of ‘structured’ design software. It is concluded that a balance must be struck between the complexity and the accuracy of the analytic models describing the interrelationship between the variables. This depends on the stage of the design optimization process. It is argued that complex optimization routines can only be justified when the process is well-defined and accurately modelled. Modelling of many systems includes approximations which have a more significant effect on the design optimization process than some of the variables.     

A comparison between Monte Carlo-calculated and -measured total efficiencies and energy resolution for large plastic scintillators used in whole-body counting

The measured total efficiency for several source positions has been determined for a large, plastic scintillation detector (NE 102A, 91.5 × 76.0 × 24.5 cm(3)) used for whole-body counting gamma spectrometry. The results have been compared with Monte Carlo-calculated total efficiencies; the code used was MCNPX 2.60. For (137)Cs, there was a good agreement between the measured and calculated total efficiencies. MXNPX was also used to calculate the electron light yield for (137)Cs; for the detector material NE 102A, Birks' constant kB was found to be 9.6 mg cm(-2) MeV(-1). The effect of light losses on spectrum resolution has been investigated for (65)Zn.     

磁轭式磁粉探伤仪提升力检测装置的开发

目前国内外相关标准规定了磁轭式磁粉探伤仪最小提升力,而实际提升力的值一直没有检测设备能够测量得到。该文根据磁轭式磁粉探伤仪提升力的定义,分析交直流磁轭式磁粉探伤仪提升力测试方法,利用单片机的步进电机控制和高速数据采集技术,开发设计出提升力检测装置。该装置使用简便,结果直观,具有实际应用价值和市场前景。     

电能计量检定生产管理系统的研究与设计

本文在分析现有信息系统特征和信息技术发展的基础上 ,详细分析了电业局电能计量检测站的工作业务流程 ,总结了原有工作流程的不足 ,提出了采用现代信息技术、条形码管理技术、计算机网络技术和现代通讯技术的表计检定生产管理系统的解决方案 ,实现了工作流程在计算机上的形式化描述和表计检定数据、流程管理数据及相关数据的集成 ,并在此基础上完成工作流的执行和管理。     

Comparison of total energy systems using gas turbines and diesel engines for combined cooling

A gas turbine engine was used to drive the compressor of a vapour compression cycle so that the usually wasted energy in the exhaust gases was partially recovered and used in the generator of an absorption cycle. The cooling effect was therefore boosted. The degree of energy utilization was further enhanced when the energy released from the absorber and condenser of both cycles was recovered in the form of hot water, which could be used for different applications. The performance parameters for this combined system, such as the cooling effect, total heat recovered and performance effectiveness ratio, were calculated for various evaporator and condenser temperatures. It was found that a system driven by a gas turbine gives a better performance than a diesel engine system under similar operating conditions.     

On the energy shift between near-field and far-field peak intensities in localized plasmon systems

The localized plasmons of metallic nanoparticles and nanostructures are known to display an interesting and apparently universal phenomenon: upon optical excitation, the maximum near-field enhancements occur at lower energies than the maximum of the corresponding far-field spectrum. Here we present an explanation for this behavior, showing that it results directly from the physics of a driven and damped harmonic oscillator. We show that the magnitude of the shift between the near- and far-field peak intensities depends directly on the total damping of the system, whether it is intrinsic damping within the metal of the nanoparticle or radiative damping of the localized plasmon.     

Dual-detector for simultaneous time and energy measurements with superconductive detectors

The development of a superconductive detector for simultaneous measurement of energy and arrival time is reported. The detector consists of two superconducting tunnel junctions coupled through a passive network. The first junction operates in the quasi-particle regime and measures the energy absorbed by counting the total charge that tunnels. The second junction uses the DC Josephson effect to act as a fast discriminator for the onset of surplus current in the first junction. The feasibility of the detector is demonstrated through simultaneous time and energy measurements of 6 keV X-rays. A model of the detector is presented and numerical simulations show good correspondence with experimental data.     

基于成像球光强测量系统的光学设计

提出一种新的快速测量空间光强分布的方法,完成基于该方法测量系统的光学系统设计,并对光学系统的关键器件进行设计.利用Matlab编程和Solidworks三维建模得到自由曲面反射镜面型,Zemax光学软件设计优化得到双高斯物镜.光线追踪仿真软件LightTools对测量系统进行模拟仿真,验证系统的可行性,并对该构架下测量系统最小角分辨率和动态范围的关键性能指标进行分析.结果表明,设计的基于成像球的测量系统可实现空间光强分布测量.     

Procedure for measuring the sensitivity of precision detectors of visible and infrared synchrotron radiation

A procedure is described for measuring the total sensitivity of photodetectors used in precision measurements of the number of low-energy (E<20 MeV) relativistic electrons from the intensity of their synchrotron radiation in the visible and infrared regions of the spectrum. The calibration constants of two types of uncooled photodetectors (a lead selenide photoresistor and a silicon photodiode) are measured, and the measurement errors are analyzed.Translated from Izmeritel'naya Tekhnika, No. 10, pp. 67–69, October, 1995.     

Digital-sampling systems in high-resolution and wide dynamic-range energy measurements: Comparison with peak sensing ADCs

The use of fast digital sampling techniques in Nuclear Physics experiments as a replacement of the standard analog signal processing methods is discussed for applications needing high-resolution signal amplitude measurements. This is for example the case of a solid-state detector with a charge-sensitive preamplifier, processed using fast digital sampling methods. Under very general assumptions, an expression for the achievable resolution and dynamic range of the system is reported, valid for any detector/digitizer/digital-filter combination, taking into account the detector noise and the ADC properties, namely the Effective Number of Bits (ENOB) and the sampling frequency. The system properties are summarized using the parameter PSENOB, i.e. the “Peak-Sensing-Equivalent Number of Bits”. These results can be used to predict the attainable performances in various applications, possibly requiring a resolution/dynamic-range trade-off. Numerical examples for some representative cases in γ-ray spectroscopy and charged particle experiments are reported, demonstrating that the equivalent performances of a 15 bit peak-sensing ADC are feasible with today-available sampling ADCs. For ease of presentation, other non-trivial effects as baseline- and non-linearity-related issues as well as experimental tests of the proposed approach are presented in a companion paper [L. Bardelli, G. Poggi, Digital sampling-systems in high-resolution and wide dynamic-range energy measurements: finite time window, baseline effects, and experimental tests, this issue].     

A design for intrinsic control of anaerobic digestion

The article reports on a novel layout which achieves intrinsic control of anaerobic digestion of a wide range of feeds on a continuous basis. The feed is automatically controlled to match the digestion rate. The design consists of a shallow tank concentric with a gas holder resting on stoppers on the tank bottom. The height of the digesting fluid is maintained using the plug flow principle. The feed material is dropped into the annular space which is thereafter covered with a black plastic sheet to enable anoxic conditions to prevail. The bioliquid hydrolyses the material, with the help of prefermenting bacteria, into volatile acids. A steady migration of these volatile acids into the anaerobic digester is maintained by the concentration gradient, which is constantly replenished by the action of a syntrophic community of bacteria, producing methane. Further, the feasibility of the concept is reported on a system with a 45 m³ concrete tank and a 35 m³ steel gas holder by using a mix of domestic wastes and producing gas with 70% methane content reliably for hundred days continuously. A novel simulator is developed to predict the performance of the design at various parameters of operation. It is shown that the performance data for digesters analogous to the design reported here are interchangeable. Based on this, the average productivity of gas for various loadings is predicted within ±10% of the actual yields for the analogous digesters. Because of the nature of the design, digestion of a wide range of feeds are permitted: without the problems faced in conventional layouts. This tremendous potential is realised by maintaining the integrity of the ecosystem of anaerobic digestion through the medium of the bioliquid which pervades the annular space as well as the confines of the anaerobic digester. By utilising the design in practice at normal loadings, its potential for reliable and economic digestion at a fraction of the cost of deep digesters could be realised if the predictions are confirmed at higher loadings by further work. This work has been carried out in the Tata Electric Companies partly in the program on renewable resources.     

产品基因及其在能量转换功能求解中的应用

 提出了能量转换型原理解的产品基因模型,构造了能量型产品基因知识库,建立了基于产品基因的启发式原理方案求解模型,并给出了求解实例。     

Experimental determination of absolute efficiency and energy resolution for NaI(Tl) and germanium gamma ray detectors at energies from 2.6 to 16.1 MeV

Measurements have been made to characterize the response of NaI(Tl) and Ge(Li) gamma ray detectors to gamma rays in the energy range of 2.6 to 16.1 MeV. Both absolute efficiency and energy resolution are reported. At 16.1 MeV the absolute full energy efficiency of a 10 cm × 10 cm NaI(Tl) detector is about 2% and the energy resolution is also about 2%. For a 65 cm³ Ge(Li) detector, the full energy peak absolute efficiency at 16.1 MeV is 0.2% (the escape peak efficiencies are 5 times larger), and the fwhm energy resolution is about 0.1%.