入射离子特征X射线分析研究

为了开展重核同量异位素鉴别方法研究,建立了入射离子特征Ｘ射线测量方法,开展了利用入射离子Ｘ射线法的应用工作。     

一台用于加速器质谱测量的充气飞行时间探测器

研制了一种新型的气体探测器－充气飞行时间探测器。介绍了充气飞行时间谱仪的原理、结构和初步的在线调试结果。     

用于加速器质谱测量的长寿命核素182Hf标准样品的制备

介绍了用于加速器质谱(AMS)测量的182Hf标准样品的研制过程.主要包括四个步骤:1、放射性核素的人工合成;2、同位素比值的准确测定;3、标准样品的稀释;4、AMS测量样品HfF4的制备.目前,合成标样的起始同位素比182Hf/180Hf的TIMS测定结果为(2.33±.07)×10-6,并研制出了一系列标准样品,182Hf/180f的比值从10-6到10-13,并且给出了不同比值标准样品的不确定度.     

A new HVE 6 MV AMS system at the University of Cologne

CologneAMS is the new Centre for Accelerator Mass Spectrometry (AMS) at the University of Cologne. It will operate a dedicated AMS system designed to measure all standard cosmogenic nuclides (¹⁰Be,¹⁴C,²⁶Al,³⁶Cl, ⁴¹Ca,¹²⁹I) and which uses a 6 MV Tandetron™ accelerator equipped with an all solid-state power supply, foil and gas stripper. The system also enables a sensitive detection of heavy ions up to ²³⁹U and ²⁴⁴Pu. The high-energy mass-spectrometer consists of a 90 degree magnet with a radius of 2 m and a mass-energy product of 351 AMU MeV to allow the detection of ²⁴⁴Pu⁵⁺ up to the maximum terminal voltage of 6 MV. This magnet is followed by an electrostatic energy analyzer and a switching magnet that can transport the rare isotope beam into various beamlines. The switching magnet forms a third analyzing element which is needed especially for the sensitive detection of heavy elements. So far two beamlines are equipped with their own detection system. One of these lines is used for suppression of isobaric background in the case of the analysis of e.g. ³⁶Cl. This is accomplished by an absorber foil which generates a Z-dependent energy loss in combination with a momentum/charge-state selection via a 120 degree magnet that features up to 30 mrad acceptance for efficient beam transport.In this contribution we will introduce the new Centre, the layout and specific characteristics of the AMS system as well as the main topics of the future scientific work to be performed at CologneAMS.     

带交叉流浓相换热器预分解窑的气体力学分析

与传统NSP窑系统相比,交叉流浓相换热器窑有着较好的热交换效果,出C1筒温度可低于250℃,可以合去增湿塔,简化工艺,是一种较好的预分解系统。从气体力学分析,交叉流浓相换热器窑气体量分配、阻力平衡较传统NSP窑复杂,但是只要把握了关键的几个气体动力源、等压点、零压点,是完全可以正常运行的。无论交叉流浓相换热器,还是传统NSP窑,必须注重低限风速的意义,防止或减少积料、塌料现象的发生;分解炉与回转窑的风量分配是提高该类窑型综合效能的关键。     

Recent advances in AMS of Cl with a 3-MV-tandem

Accelerator mass spectrometry (AMS) of ³⁶Cl (t_1/2 = 0.30 Ma) at natural isotopic concentrations requires high particle energies for the separation from the stable isobar ³⁶S and was so far the exclusive domain of tandem accelerators with at least 5 MV terminal voltage. Using terminal foil stripping and a detection setup consisting of a split-anode ionization chamber and an additional energy signal from a silicon strip detector, a ³⁶S suppression of >10⁴ at 3 MV terminal voltage was achieved. To further increase the ³⁶S suppression energy loss straggling in various counter gases (C₄H₁₀, Ar-CH₄ and C₄H₁₀-Ar) and the effect of “energy focusing” below the maximum of the Bragg curve was investigated. The comparison of experimental data with simulations and published data yielded interesting insights into the physics underlying the detectors. Energy loss, energy straggling and angular scattering determine the ³⁶S suppression. In addition, we improved ion source conditions, target backing materials and the cathode design with respect to sulfur output and cross contamination. These changes allow higher currents during measurement (³⁵Cl⁻ current ≈ 5 μA) and also increased the reproducibility. An injector to detector efficiency for ³⁶Cl ions of 8% (16% stripping yield for the 7+ charge state in the accelerator, 50% ³⁶Cl detection efficiency) was achieved, which can favorably be compared to other facilities. The memory effect in our ion source was also thoroughly investigated. Currently our measured blank value is ³⁶Cl/Cl ≈ 3 × 10⁻¹⁵ when samples with a ratio of 10⁻¹¹ are used in the same sample wheel and ³⁶Cl/Cl ≈ 5 × 10⁻¹⁶ if measured together with samples with a ratio of 10⁻¹² or below. This is in good agreement with the lowest so far published isotope ratios around 5 × 10⁻¹⁶ and demonstrates that 3 MV tandems can achieve the same sensitivity for ³⁶Cl as larger machines.     

Knowledge-based picture understanding of weather charts

This paper describes a knowledge-based weather chart understanding system named WERP, which is working as a picture processing part of our Information understanding System Of BAsic weather Report (ISOBAR). WERP is designed to extract necessary information from a weather chart for generating weather report sentences explaining the chart. This system is based on a structural model of the weather charts.Here, we study what problems are involved in weather chart understanding, how they are solved and how an actual system is organized. Also, picture-processing techniques for weather chart processing and some experimental studies are considered.     

三角网格法绘制等水压线若干问题的研究

三角网格法是自动生成管网等水压线最常用的方法,而在实际管网中,由于管线较为复杂,只将节点作为离散数据点绘制的等水压线往往误差较大.通过分析三角网格法的特点,对于管段提出了三角形边覆盖全部管段的离散数据点的收集原则,并针对曲线管段、存在折点的管段、较长管段和跨接管段四种情况给出了具体的处理方法;对于阀门和水泵提出了等效管段法以正确反映水压的突变.同时结合工程实际,讨论了适当取舍要素和选取离散数据点范围的问题.实践证明,依据此方法绘制的等水压线能够更为准确地反应管网中水压的变化情况.     

An experimental apparatus proposed for efficient removal of isobaric contaminants in negative ion beams

Isobaric contaminants are often problematical in accelerated negative ion beams for research at certain radioactive ion beam (RIB) and accelerator mass spectrometry (AMS) facilities since their presence in low-intensity rare isotopic beams seriously compromise experimental results. This article describes a non-resonant, laser-based photo-detachment apparatus for use at these facilities, which, according to calculations efficiently removes isobaric contaminants from these beams. The advantage of the system for isobaric contaminant removal over other systems proposed to date lies in its ability to efficiently capture easily transportable energetic negative ion beams with low, intermediate or high energy spreads by a superconducting solenoid magnetic field. The ability to change the diameter of captured beams by adjusting the magnetic field strength permits optimum control of the radial overlap of the laser/negative ion beam profiles over an extended interaction region under high vacuum conditions without retarding optical affect, collision-cooling or capture losses.