自由电子激光相干强太赫兹源装置鬼脉冲初步研究

研究中国工程物理研究院自由电子激光相干强太赫兹源(FEL-THz)装置上鬼脉冲产生的原因及其对装置调试测量的影响,通过束流动力学模拟、热分析、蒙特卡罗模拟以及初步实验结果分析,证明了鬼脉冲将会明显破坏阻拦型测量,并会在束线管道上造成温度升高和辐射强度增大。研究表明:鬼脉冲成为限制FEL-THz装置正常工作的重要原因,为保证FEL-THz顺利出光,鬼脉冲必须予以消除,并简要讨论了鬼脉冲的消除方法。     

强流质子加速器PXIe控制器的子控制系统

针对一台用于加速器驱动次临界系统(ADS)的强流质子加速器,即ADS注入器Ⅱ,开展其定时系统和快保护系统的研究工作,设计了一款可在这两个系统中应用的PXIe控制器。该控制器基于现场可编程门阵列设计,可实现光纤通信、PXIe总线通信、延时触发信号输出等功能。其中,光纤通信功能用于实现各PXIe控制器之间的数据传输;PXIe总线通信功能主要是为了实现控制器与工控机之间的数据交互;延时触发信号输出功能可以给出精确的低电压晶体管-晶体管逻辑电平标准的时序触发信号,从而保证加速器的各子系统和设备能够按照一定的时序协调一致地工作。     

Identification of striking distance considering the velocity ratio and competition among the leaders

The striking distance is an important parameter to design a reliable lightning protection system. To protect an object against direct strikes, an improved leader progression model combined fractal geometry and the leader initiation criteria proposed by M. Becerra is introduced to determine the striking distance on a given structure. Both the deterministic and stochastic features of the lightning leader are considered and more detailed three-dimensional numerical simulation of the leader discharge is achieved due to the application of extended grid. Some of the basic methods and strategies are outlined and the influence on protection zone caused by leader velocity ratio is analyzed. Moreover, a comparative analysis of the results obtained through the improved model, the rolling sphere method and the Cooray model is performed. The results indicate that the presented method is closer to the natural lightning and the selection of the breakdown point is actually a complex competitive process among numerous upward leaders.     

192Ir-Applikator zur endolaryngealen Strahlenbehandlung Umschlossene radioaktive Strahlungsquellen X.

Es wird ein ¹⁹²Ir-Applikator zur endolaryngealen Strahlenbehandlung beschrieben. Er dient der perendoskopischen, epitumoralen Applikation wählbarer Strahlendosen für Gewebevolumina von etwa 2 ml. Die Probleme des Strahlenschutzes und der Enkoskopie sind lösbar, wie erste klinische Anwendungen bestätigen.     

15N natural abundance of non-fixing woody species in the Brazilian dry forest (caatinga)

Foliar δ¹⁵N values are useful to calculate N₂ fixation and N losses from ecosystems. However, a definite pattern among vegetation types is not recognised and few data are available for semi-arid areas. We sampled four sites in the Brazilian caatinga, along a water availability gradient. Sites with lower annual rainfall (700 mm) but more uniform distribution (six months) had δ¹⁵N values of 9.4 and 10.1 ‰, among the highest already reported, and significantly greater than those (6.5 and 6.3 ‰) of sites with higher rainfall (800 mm) but less uniform distribution (three months). There were no significant differences at each site among species or between non-fixing legume and non-legume species, in spite of the higher N content of the first group. Therefore, they constitute ideal reference plants in estimations of legume N₂ fixation. The higher values could result from higher losses of ¹⁵N depleted gases or lower losses of enriched ¹⁵N material.     

Probleme,Methoden, Analysen- und Meßverfahren im nuklearen Umweltschutz

Es werden die wesentlichsten Probleme und Aufgaben des Umweltschutzes hinsichtlich der verschiedenen Komponenten der natürlichen und zivilisatorischen Strahlenbelastung, die Überwachung auf Radioaktivität als Folge der Kernwaffenversuche und die Umgebungsüberwachung von Kernanlagen beschrieben.

Es wird ein Überblick über die verschiedenen Bestimmungsmethoden der Radionuklide, die Schritte der Probenaufbereitung, die zur Alpha-, Beta- und Gammamessung verwendeten Verfahren sowie die Meßwertverarbeitung gegeben.     

Vereinheitlichte gynäkologische 60Co- und 137Cs-Applikatoren

Am 8. und 9. November des vergangenen Jahres fand in Magdeburg das I. Strahlenschutzkolloquium für Kontakttherapie in der Medizin statt. Veranstalter war die Staatliche Zentrale für Strahlenschutz. Als ein wichtiges Ergebnis dieser Tagung kann die seit langem angestrebte Einigung über die vom Hersteller (Institut für angewandte Isotopenforschung, Berlin-Buch) vorgeschlagenen Konstruktionsparameter gynäkologischer ⁶⁰Cound ¹³⁷Cs-Applikatoren angesehen werden, die in einer vom Vorsitzenden der Problemkommission ?Radiologie” (Prof. Reicliel) einberufenen Sondersitzung unter Teilnahme von 30 Klinikern, Strahlenphysikern und Vertretern des Instituts für angewandte Isotopenforschung erzielt wurde.     

Prospects and Limitations of an Isotope Tracer Technique for Understanding Sulfur Cycling in Forested and Agro-Ecosystems

Abstract

Applications of isotopically distinct sulfur compounds have recently been used for tracing the fate of added sulfur in whole catchments or sub-compartments therein. Basic principles, the analytical methodology, and data evaluation for this isotope tracer technique are briefly described. We recommend that δ³⁴S-values of applied and natural sulfur compounds in the investigated ecosystem should differ by more than 20‰ in order to successfully ascertain sulfur fluxes. Where possible, a high ratio of applied sulfur loads versus sulfur pool sizes in the ecosystem should also be realized in order to allow the assessment of sulfur transformations in the study area. Prospects and limitations of this isotope tracer technique are critically discussed by reviewing results from recently or currently conducted lysimeter and field experiments.     

Use of optical properties of LiF in radiation protection dosimetry

Optical absorption spectra of LiF:Mg, Ti thermoluminescence (TL) materials have been determined and used in radiation absorbed dose measurements. Samples were irradiated with different gamma doses (0???1.022 Gy) with dose rate of 12.78 mGy/min and also for different X-ray beam qualities. It was found that there is no significant absorption edge, and the optical absorption increases with increasing gamma doses. Peak intensities of trapping levels showed a linear increase with increasing X-ray or gamma doses. The variation of the optical density with X-ray or gamma doses is energy independent. The TL readings were not affected when the samples were first measured optically. The linearity of the optical density–dose relationship is found to be useful in radiation protection dosimetry.     

A constraint satisfaction method applied to the problem of controlling the CO2 emission in the Legal Brazilian Amazon

Socioeconomic-driven processes such as deforestation, forest degradation, forest fires, overgrazing, overharvesting of fuelwood and slash-and-burn practices constitute the primary sources of Greenhouse Gases (GHG) emissions in developing countries. Climate policies can induce the development of clean technology and offer incentives to accelerate reforestation. The Brazilian government has already acknowledged the urgency to invest in policies to reduce anthropogenic CO₂ emissions in the Legal Brazilian Amazon (BA). In this work, we propose a scheme to estimate the required investments in clean technology and reforestation to achieve a prescribed short term target value for the atmospheric CO₂ emission. Initially, a mathematical model is fitted to the available data to allow forecasting the values of the short term emissions of CO₂ under a combination of investments in clean technology and reforestation. The investments to reduce the emissions of CO₂ below a target value (400 million tons/year, starting at the initial value of 450) in 3 years’ time are proportional to the regional GDP. Using computer simulation it is possible to generate a range of possible investment values in clean technology and reforestation, so that the prescribed emission reduction is achieved without hindering economic growth. This strategy provides the necessary investment flexibility for the implementation of realistic climate policies.