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。     

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)     

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.     

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.     

Carbon carbon detection: Diamond detectors and AMS

¹⁴C ions (290 keV) have been detected with chemically vapour deposited diamond. Potential benefits of diamond detectors are radiation hardness, high charge collection and very fast response time/high bandwidth.     

Improving AMS uncertainties and detection of instrumental error

We emphasize the estimation of uncertainties of AMS results and the detection of instrumental error in the framework of commonly used methods of AMS data-analysis.The conventional methods are fast but raise the following four issues: (1) observed sampling variance has scatter that may lead to some true values being over five standard errors away from the mean. (2) Use of the Gaussian distribution for the end-result is unwarranted in several cases. (3) The standard error of the mean is slightly biased due to sampling and correlations. (4) Detection of instrumental errors could be improved. The Bayesian CAR model that we have introduced carries the calculations out with full probability distributions and uses an overall probabilistic process to describe the instrumental error. The scatter in the uncertainties given by CAR is an order of magnitude smaller than that of the sampling-based uncertainties, resulting in more reliable uncertainties. Compared to previous methods, better detection and estimation of instrumental error is also achieved.     

High precision C AMS at CIRCE

The CIRCE AMS system started operation in March 2005. The measurement of isotopic ratios ¹⁴C/¹²C in samples of archaeological and environmental interest has rapidly attained high precision and accuracy levels in routine operation. The results of the intercomparison campaign in the framework of the VIRI program, as well as the outcome of a statistical analysis of the about 200 control measurements performed with standard samples, have shown the capability of the whole system for high precision measurements (δR/R < 0.3%), allowing systematic investigations in both archaeological and environmental sciences. ²⁶Al AMS has been implemented for the measurement of the astrophysically relevant ²⁵Mg(p,γ)²⁶Al reaction cross section, while a beam line is under construction for the measurement of actinides isotopic ratios.     

核电在我国应对气候变化中的作用和意义

通过分析国际气候谈判形势和国内减排压力,按照到2020年中国核电总装机容量要达到4000万千瓦或有可能达到7000万千瓦的核电建设目标,从发电环节和核电链分别测算核电相对火电的减排作用,说明核电在应对气候变化中的重要意义,并提出相应政策建议。     

AMS Measurement of ^93Zr

The zirconium isotope ^93Zr is a long-lived pure beta-particle-emitting radionuclide, which is produced by nuclear fission and neutron activation of the stable isotope ^92Zr. This element is a constituent of the structural components of nuclear reactor vessels. With AMS it should be possible to detect minute amounts of ^93Zr. A Silica gel adsorption chromatography method for radiochemical separation of Zr has been developed to reduce the stable isobar ^93Nb, which is the main interference for the detection.     

Improvements of the Jena AMS system

A new slit stabilization circuit and a modified generator drive were installed on an AMS system based on a 3 MV Tandetron?, produced by High Voltage Engineering Europa (HVEE). Furthermore our test procedure used at the Jena AMS system for the rectifiers of the Cockroft–Walton generator is presented.     

Highly sensitive AMS measurements of 53Mn

Our AMS system, with the gas-filled detector system GAMS, has been optimized for measurements with ⁵³Mn. A high sensitivity has been achieved. A newly installed cesium sputter ion source yields an improved emittance, and thus a higher mass resolution. By the extraction of the manganese molecule MnF^? instead of MnO^? we can suppress the isobaric chromium background in the ion source by more than a factor of three. The GAMS system achieves an isobaric suppression factor of about 3 × 10⁸. Measurements on blank samples yielded upper limits for the ⁵³Mn/⁵⁵Mn ratios of 7 × 10^?15.     

Isobaric identification techniques of AMS at CIAE

Some long-lived nuclides, such as ³⁶Cl, ⁴¹Ca, ⁵³Mn, ⁷⁹Se, etc., are very interested in life science, environment science, geo- and cosmo-sciences, nuclear wastes management, and other fields. Taking the advantages in high sensitivity and the strong ability to reduce the interferences from molecular ions and isobars, AMS has been one of the most promising methods for the measurement of these nuclides. However, the sensitivity of AMS is often unsatisfactory due to the interferences of stable isobars especially for medium and heavy radioisotopes. Gas-filled time of flight (GF-TOF), Gas-filled Magnet with a time of flight (GFM-TOF), Bragg Curve detector and energy loss (ΔE) combined with a Q3D magnetic spectrometer (ΔE-Q3D) are among the techniques used or being developed in AMS lab of China Institute of Atomic Energy, in an attempt to further reduce the interferences from isobars. These techniques will be tested in our AMS measurement of ⁵³Mn, ⁷⁹Se, ⁹³Zr, ⁹⁹Tc, etc., for identifying isobaric interferences.     

北京大学加速器质谱计注入系统

北京大学加速器质谱计的注入系统采用快交替注入技术，注入磁铁分辨率高、强峰拖尾抑制能力强。为提高传输效率、减小分馏效应，在束线设计中采取一系列措施，充分考虑ＡＭＳ的特殊要求。文章给出该注入系统的物理设计与调试测量结果。     

AMS专用高分辨注入器系统研制

研制了北京HI-13串列加速器AMS专用高分辨注入器系统.静电分析器和磁分析器构成能量消色散系统,质量分辨率可达600以上,传输效率好于80%.     

Future of the NOSAMS Tandetron AMS system

The NOSAMS 3 MV Tandetron AMS system will soon reach its 20th anniversary of operation. A critical review of all aspects of the system is necessary to assess the analytical, economical and operational factors that enter into the consideration of either an upgrade or a replacement of the instrument. Recent in-house experience with the design and construction of a large-acceptance ¹⁴C AMS system gives us a benchmark with which to compare the expected outcome of an upgrade. The present ion analysis efficiency of our Tandetron system is roughly 1%, well below the 4% value of our new system. This affects the lower limit of analyzable sample size, speed of analysis, exposure to systematic errors, and the upper limit of achievable single-sample counting statistics. At first glance it may seem obvious that a replacement (even at higher cost) would be preferable to an upgrade. However, it will be shown that there are good reasons to consider the latter. One of the most compelling is the fact that the Tandetron is a state-of-the-art and superior high-current accelerator design with minimal signs of aging and very low-maintenance. Ion beam modeling calculations show that the main transmission limitation of the instrument is caused by the design of our injector, a four-magnet “Recombinator”, making it difficult to perform reliable AMS with negative currents exceeding 80 μA. To be acceptable, an upgrade should bring the Tandetron to at least 3% ion efficiency by replacing the injector with a properly matched high-transmission device.     

加速器质谱测量用HfF4样品的制备研究

研究了用于加速器质谱(AMS)测量的HfF4样品的制备方法.通过分离纯化流程和HfF4的制备流程,将HfO2样品制成符合加速器质谱测量用的HfF4.流程去杂质能力很强,特别是对钨的去污,样品基本满足测量要求.全流程产额约为70%,对钨的去污系数约为106.