基于加速器质谱的新型双用注入系统设计

提高14C的测试精度和10Be、26Al等长寿命放射性核素的丰度灵敏度是加速器质谱(AMS)领域的热点问题之一.西安加速器质谱中心设计了一套基于HVEE公司4130型加速器质谱计的双用注入系统.通过速度分析器的作用,在一套系统上实现交替注入和同时注入两种工作模式,较大程度上简化了以往两套系统共存的布局.计算结果表明,此系统既可以进行10Be、26Al的超高灵敏度测量,又继承了4130型AMS高精度的14C测试能力,拓展了其测量核素的范围.     

西安加速器质谱仪的运行和工作状况

西安加速器质谱仪(Xi'an-AMS)于2006年8月正式投入运行.在近两年的分析测试中,仪器运行正常,成功测试了14C、10Be、26Al和129I等共2 741个待测样品,对外测试服务占总测样品数比例达50%.为进一步优化仪器的测试性能,提高测样效率,西安加速器质谱中心与荷兰高压静电公司(HVEE)合作,对原有离子源部分进行升级改造,并对计算机控制部分做了优化.改造后的离子源头可以长时间稳定运行,且在14C测量中未发现记忆效应.     

AMS 10Be测量本底研究和改进

10Be是加速器质谱(AMS)测量中重要性仅次于14C的核素,在第四纪地质研究等方面发挥着重要作用.为开展岩石暴露年龄测定和黄土中10Be含量测量等应用研究,北京大学加速器质谱(PKUAMS)在设备改进的基础上对10Be测量本底进行了较为系统的研究,使测量本底达到了6×10-15.本工作主要介绍AMS 10Be测量本底的主要来源,从提高10Be离子计数率与抑制7Be干扰本底两个方面对10Be测量本底进行了较为系统的研究与改进.     

黄土样品的BeO制备及AMS测量

采用常规方法提取黄土-古土壤样品中的10Be,制备BeO样品时,无法有效降低样品中B含量,导致在10Be AMS测量中本底值偏高.本文对BeO制备方法进行了优化.新的制备流程改进了阳离子树脂交换、Be(OH)2转化为BeO的灼烧方式以及实验所采用的仪器设备.在西安加速器质谱仪(Xi'an-AMS)上测试结果表明,采用该化学流程制备的BeO样品化学本底可以达到2.04×10-14.本文还介绍了Xi'an-AMS测量10Be的方法与测量结果.     

加速器质谱研究超重核进展

超重核的研究具有重要的科学与实际意义。目前,在自然界直接寻找超重核的方法主要包括普通质谱（ICP-SF-MS）,加速器质谱（AMS）及多重中子探测的方法等。相比其他方法,AMS具有灵敏度高、样品用量少、测量时间短等优势。本文综述了近年来国内外利用AMS寻找超重核的方法及现状。迄今为止,利用AMS寻找了40余种超重核素,但没有明显的证据表明超重核的存在,这些核素与其矿物主体元素的丰度比约在10^-12到10^-16之间。     

上海原子核研究所的6MV串列静电加速器质谱计及其应用

加速器质谱计(AMS)是70年代末发展起来的超微量分析技术,它与常规质谱计比较,可以利用某些元素不能形成负离子的性质和将待测同位素加速至较高能量(～MeV/A)用粒子鉴别器排除同质异位素的干扰,并在剥离器将分子离子破裂成原子离子,然后被电磁元件排除。它与测量放射性方法比较,具有探测效率较高、不需要对样品作放化提纯、对非放射性同位素也同样有效等优点。因此它具有灵敏度高(10~(-12)     

~(10)Be/~9Be标准样品的制备和加速器质谱测量

按重量法用高纯度的天然Be的化合物BeSO4·4H2O稀释10Be/9Be标准参考物质SRM4325,制备系列同位素比标准样品。在北京HI-13串列加速器的AMS系统上对该系列标准(10Be/9Be比值为2.68×10-11～2.38×10-12)进行测量。结果表明,10Be/9Be比值测量值与标称值有很好的线性关系,并且经SRM4325归一化后的测量值与标称值吻合,其比值在0.96～1.06之间。这表明该系列标准样品能够用于北京HI-13串列加速器AMS系统对地质环境样品中10Be/9Be绝对比值的测定中。~(10)Be/~9Be标准样品的制备和加速器质谱测量@李世红 @何明 @姜山 @管永精…     

中重核加速器质谱测量实验谱的预先研究

加速器质谱(AMS)测量需排除同位素和同量异位素及其它本底的干扰。在中重核素的AMS测量中，干扰本底尤为严重，这给在束确认实验谱中所对应的各核素和实验谱的核素分析带来一定困难。为解决这一问题，我们设计编写了中重核加速器质谱测量实验谱的模拟程序，它可在实验前预先设定最佳实验条件和给出待测核素及可能进入超灵敏加速器质谱探测器中的各干扰核素的计算值。利用该程序的计算结果对照实验测量数据，可在束确认实验谱中的待测核素。     

加速器质谱计在地球科学中的应用

本文介绍加速器质谱计用于测定天然物质中超微量同位素~(10)Be及其在地球科学中的应用。环绕样品~(10)Be的测定可用于研究大气和海洋中发生的各种传输作用过程;大陆沉积物~(10)Be分布及迁移直接与黄土(或土壤)的堆积和侵蚀有关。~(10)Be是一种反映各种地球化学作用过程的理想的示踪剂。     

3 MV加速器质谱测量36Cl

在端电压为3 MV的AMS装置上实现³⁶Cl及其他中重核素的高灵敏测量是AMS技术发展的重要方向之一。为进一步提高充气飞行时间探测方法中³⁶S的压低能力,本文研究了³⁶S和³⁶Cl在P10、异丁烷和丙烷气体中的能量歧离和角度歧离。在32 MeV的入射能量下测量了几个地下水样品中³⁶Cl的[JP2]含量,测量结果与72 MeV能量下的测量结果相符。测量结果表明,采用充气飞行时间探测方法在3 MV的串列加速器上测量³⁶Cl时,探测限为³⁶Cl/Cl≈10^-14,当样品中³⁶Cl/Cl≈10^-13时测量不确定度为30%。     

AMS实验

全面概述AMS实验的物理目标、组成1998年飞行的阿尔法磁谱仪（AMS－01）各子探测器的性能以及AMS－01的初步实验结果。     

Developments in micro-sample 14C AMS at the ANTARES AMS facility

We continue development of micro-sample radiocarbon sample preparation and AMS measurement at the ANTARES AMS facility. We routinely prepare samples containing 10–200 μg of carbon using an iron catalyst with an excess of hydrogen in ～2.5 mL graphitisation reactors. These use a tube furnace to heat the catalyst to 600 °C and a Peltier-cooled water trap. Samples containing just a few micrograms of carbon can be prepared. We describe progress with a 0.5 mL laser-heated ‘microfurnace’ we are developing for the rapid and efficient graphitisation of ～5 μg samples. Following operating experience with a prototype unit, work has commenced on the development of a second-generation device with the goal of fully automated operation with minimal introduction of extraneous carbon.Key to development of micro-sample ¹⁴C AMS is the ability to reliably handle the graphite/iron sample and to mount it in the ion source target holder. We have developed a target holder that permits the sample to be loaded in a 1 mm diameter recess and rear pressed, ensuring a high quality surface finish, at a reproducible depth. Additionally we have developed a method for systematically aligning the sample stage with the cesium beam following ion source servicing.     

Superconducting minicyclotrons in AMS

The limitations of conventional mass spectrometry are studied. Cyclotron-based accelerator mass spectrometry techniques are discussed. The design and applications of superconducting minicyclotrons dedicated to the radioisotope dating, cosmochronology and complex-fragment radioactivity researches are discussed.     

SUERC AMS ion detection

In a short time Be, C, Al, Cl, Ca and I accelerator mass spectrometry (AMS) have been established on the National Electrostatics Corporation (NEC) 5 MV pelletron system at the Scottish Universities Environmental Research Centre (SUERC). While summarising the present performance of the system, this report will focus on the details of ion detection, which sample materials are used and the analytical procedures employed for each individual species during routine analysis.All rare isotope detection is with a single flexible detector and ion event analysis system, but switching of analysed species typically requires a detector reconfiguration. Configurations for routine ¹⁰Be, ¹⁴C, ²⁶Al, ³⁶Cl, ⁴¹Ca and ¹²⁹I detection have been established and will be presented here. Notably, there has proven to be sufficient suppression of the isobaric interferences of ³⁶Cl and ⁴¹Ca in the 5+ charge state using an argon gas stripper at a terminal voltage of 5.0 MV to allow for routine analysis of these isotopes.     

一台AMS的静电偏转器

文章描述一台静电偏转器的设计、结构和调试。静电偏转器的角度为15°,曲率半径360cm,两板面距离3cm。两板正负电压已达到 92.4 kV和-80kV,电场梯度为57.5kV/cm。该静电偏转器用作加速器质谱计(AMS)的能量分析。     

Attempted positive ion radiocarbon AMS

The SUERC single-stage accelerator mass spectrometer is capable of generating and accelerating-from-ground positive ions. Having previously shown suppression of molecular interferences we have proceeded to study positive ion radiocarbon AMS. Potential benefits are convenient and efficient ion production. This depends on overcoming the large ¹⁴N atomic isobar which we have suppressed by seven orders of magnitude in the accelerator terminal. A remaining interference is more problematic, however.     

Software development for continuous-gas-flow AMS

The National Ocean Sciences Accelerator Mass Spectrometry (NOSAMS) Facility at Woods Hole Oceanographic Institution is presently completing installation of a novel continuous-flow AMS system. A multi-year development of an AMS microwave gas ion source in collaboration with Atomic Energy Canada Limited (AECL), Chalk River, has preceded this final step of an implementation that is expected to add a new dimension to ¹⁴C AMS. National Instruments, NIM, and CAMAC modules have been programmed with LabVIEW on a Windows XP platform to form the basis for data acquisition. In this paper we discuss possible applications and include simulations of expected data acquisition scenarios like real-time AMS analysis of chromatograms. Particular attention will have to be given to issues of synchronization between rapidly changing input amplitudes and signal processing cycles in hardware and software.     

Study of Super-heavy Nuclei with AMS

There are significantly scientific and practical significance for the study of super-heavy nuclei. Currently, the methods for the study of searching for super-heavy nuclei in nature mainly include ordinary mass spectrometry methods such as ICP-SFMS, accelerator mass spectrometry (AMS) and the method of multiple neutron detection. Compared to the other methods, AMS have some advantages, such as high sensitivity, small sample size and short measuring time. The methods and the status of searching for super-heavy nuclei with AMS at home and abroad in recent years were reviewed. Until now, more than 40 species of super-heavy nuclides have been searched with AMS. There was no clear evidence of the existence of super-heavy nuclei. The abundances of these nuclides with respect to host elements of mineral were about 10^-12 to 10^-16.