中国原子能科学研究院的PX-AMS系统及其应用(英文)

加速器质谱(AMS)中的入射离子X射线方法是为解决AMS测量中重核同量异位素而发展的一种方法(PX AMS),在中国原子能科学研究院建立了PX AMS方法之后,利用这套系统开展了79Se,75Se,64Cu等核素的PX AMS方法测量,基于此技术实现了79Se,75Se半衰期的测量和64Cu放射性核束强度及库仑激发截面的测量。     

Absolute determination of 79Se/80Se with AMS

Selenium-79 measurement with accelerator mass spectrometry (AMS) is increasingly being used for the determinations of ⁷⁹Se relevant nuclear data. Furthermore, ⁷⁹Se was deemed to be an ideal tracer nuclide for long-period and non-intrusive biological studies on selenium. An ultra-sensitive AMS measurement method of ⁷⁹Se has been established at the CIAE-AMS system. For further applications of ⁷⁹Se-AMS, reference standards were requested. ⁷⁹Se can be derived from the ⁷⁸Se(n, γ)⁷⁹Se reaction but cannot be accurately quantified by theoretical calculation owing to the small and dubious cross section and other relevant parameters. In this paper, an AMS method has been developed for the absolute determination of the ⁷⁹Se/⁸⁰Se ratio in a ⁷⁹Se sample with relatively high ⁷⁹Se content. The relative standard uncertainty of ⁷⁹Se/⁸⁰Se ratio is 4.7% and a reference standard is thus acquired. The results are favourable for further applications of ⁷⁹Se-AMS.     

重核离子束成分的加速器质谱分析

为拓展加速器质量技术测量范围及测量放射性核束成分,建立了利用入射离子发射特征Ｘ射线鉴别同量异位素的方法,开展了利用ＡＭＳ测量重核离子束成分的工作。     

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.     

79Se半衰期计算

介绍了用log ft系统学计算⁷⁹Se半衰期的方法。根据系统学计算和与实验测量数据的比较，推荐了⁷⁹Se的半衰期。给出了⁷⁹Se衰变纲图并计算得到了⁷⁹Se辐射数据。      

从高放废液中分离79 Se的流程研究

建立了离子交换法与沉淀法相结合的、从高放废液中分离79Se的放化流程.该流程具有去污效果好的特点,对137Cs,90Sr,90Y,99Tc,154Eu的去污因子大于104,对125Sb,113Sn的去污因子大于103,对237Np为2×102.整个流程的收率约为53%.由该流程分离出的79Se样品能够很好地满足液闪测量和质谱测量的要求.     

79Se的AMS测量方法研究

测定⁷⁹Se时由于⁷⁹Se尚无标准样品,需要建立⁷⁹Se/Se（⁷⁹Se、Se原子个数比,余同）的AMS测量方法。在⁷⁹Se/Se的绝对测定中,为尽可能避免测量Se的同位素之间的差异,通常利用探测器测量⁷⁹Se离子,本文用法拉第筒对⁷⁸Se和⁸⁰Se进行测量,但这造成两个测量系统之间的系统误差。为避免这种系统误差,利用同一探测器测定⁷⁹Se、⁷⁸Se和⁸⁰Se。考虑到⁷⁸Se和⁸⁰Se的计数率非常高,在CIAE-AMS系统中的静电分析器前和靶室内安装衰减片以降低⁷⁸Se和⁸⁰Se的计数率。实验结果表明：通过两个衰减片的衰减作用,能将⁷⁸Se和⁸⁰Se的束流降低到半导体探测器的检测范围内,实现了样品中⁷⁹Se/Se的绝对测定,得到⁷⁹Se/Se为(2.08±0.10)×10^-7,为准确测定⁷⁹Se半衰期奠定了基础。     

Determination of the detection limit of Ni at the Lund AMS facility by using characteristic projectile X-rays

Accelerator mass spectrometry (AMS) is an ultra-sensitive method for counting atoms, both radionuclides and stable nuclides. When using small tandem accelerators to measure heavy isotopes, interfering isobars are often troublesome. One way to reduce this interference is to combine AMS with the detection of characteristic X-rays of the projectile. After analysis in the AMS system it is possible to identify ions of different atomic number by their characteristic X-rays, by slowing down the ions in a suitable target. In this paper, the detection limit of ⁵⁹Ni at the Lund AMS facility is reported. A method for the chemical extraction of nickel from stainless steel, combined with a purification step to reduce the cobalt content in the sample by several orders of magnitude, is also described.     

The AMS measurement of 236U at CIRCE

Accelerator mass spectrometry(AMS) is an ultrasensitive technique for measuring long-lived actinides,e.g.,~(236)U,~(237)Np and Pu isotopes.In order to improve the detection limit for actinides abundance,and to increase the detection efficiency in actinides AMS measurement,a 16-strip silicon detector was used to identify actinides at the Center for Isotopic Research on Cultural and Environmental heritage in Caserta,Italy.The sensitivity of ~(236)U/~(238)U was 1×10~(-11) by special resolution and 5.0×10~(-12) by time resolution.The pulse height defect of~(236)U in an ion-implanted silicon detector in the low-energy range with 17.26 MeV is presented.     

∑HfF（5,-） current monitoring with off-axis Faraday cup in AMS measurement of ^（182）Hf at CIAE

In order to reduce the systematic uncertainties caused by the sequential injection in AMS measurement of ¹⁸²Hf,a technique for instantaneous monitoring of off-axis∑HfF₅^- current was developed in the AMS laboratory at China Institute of Atomic Energy（CIAE）.The stability and reliability of this method have been experimentally verified.As a result,the accuracy for AMS measurement of¹⁸²Hf was significantly improved.     

放射化学分离裂变产物中^79Se的新流程

因加速器质谱法（ＡＭＳ）测定＾７９Ｓｅ半衰期的需要，建立了一个从裂变产物中放化分离＾７９Ｓｅ的新流程。流程以硝基苯萃取－二氧化硫沉淀为主要步骤，避免了经典的ＳｅＢｒ４蒸馏法带来的＾７９Ｂｒ对＾７９Ｓｅ的同量素污染。流程的化学回收率大于６０％，对所要分离的各种放射性核素的去污能力满足要求。采用液闪方法测量＾７９Ｓｅ的放射性活度，并对影响活度测量的各种因素进行了详细的研究。用本流程获得的＾７９Ｓｅ可成     

Si AMS measurement with ΔE-Q3D method

Accelerator mass spectrometry (AMS) is one of the most promising methods for the measurement of trace amount of ³²Si for its advantages of small sample size, short measurement time and extremely high sensitivity. However, the isobaric interference from ³²S often badly hinders the AMS measurement of ³²Si. The ΔE-Q3D detection technique established in this work brought about an overall suppression factor of larger than 10¹² for ³²S. As a result, a sensitivity of better than 1 × 10⁻¹⁴ (³²Si/Si) has been achieved, based on the measurement of a blank sample.     

90Sr的加速器质谱测量技术研究

为开展90Sr在核环境监测、医学示踪等领域的应用,本文基于中国原子能科学研究院的加速器质谱（AMS）装置开展了90Sr的AMS测量方法研究。从负离子引出方法、AMS系统传输条件、Q3D磁谱仪的同量异位素分离技术和多阳极气体电离室的离子鉴别方法等对90Sr的AMS测量技术进行了系统研究,有效排除了测量时的本底干扰,使得90Sr的测量灵敏度达90Sr/Sr=92×10-13,为开展基于90Sr的应用奠定了基础。     

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。     

Pu同位素的AMS测量方法研究进展

锕系超铀元素Pu主要来自于各类人工核活动,现广泛存在于自然界中.其在多个基础研究及应用领域具有重要研究和使用价值,并已得到广泛应用.本文比较了目前Pu的主要测量方法,对各种方法的优缺点加以分析.在所有Pu的测量方法中,加速器质谱(AMS)方法具有样品用量小、测量时间短、能区分239Pu与240Pu,同时探测限低等优点,...     

AMS-14C样品制备系统的研制及其性能研究

为了开展加速器质谱仪（accelerator mass spectrometry, AMS）在¹⁴C测量方面的研究,研制了可采用锌法、氢法、氢化钛法制备¹⁴C样品的装置,该制样系统以石英玻璃为主要结构材料,分为以下三个单元：系统真空维护单元、CO₂纯化单元和CO₂还原单元。为验证此装置的可靠性,进行了系列 ¹⁴C样品的制备实验,得到的石墨产率基本达到80%,同时对商业碳粉、树木的含碳量与实验过程中测量区域对应的CO₂量进行了线性拟合,结果呈现明显的线性关系。对一批标准样品和本底样品进行AMS测试,结果显示每个样品¹²C^-的引出束流均大于20 μA,系列空白样品的测量结果表明,¹⁴C/¹²C丰度比平均值为1.061×10^-15,样品制备系统稳定且在制样过程中引入的碳污染较小,符合制样要求,现代木头样品的AMS绝对测量值为（9.13±0.05)×10^-13,与预期值~9.0×10^-13相符合。上述结果表明,该系统结构紧凑,能避免相互污染,高效且便于操作,满足AMS对¹⁴C样品的测试要求。     

串列加速器质谱计束流传输系统的设计特点

串列加速器用于测定~(10)Be为例,阐述质谱计(AMS)束流传输系统的设计特点。实现了对高丰度稳定同位素强峰拖尾的有效抑制和束流“平顶传输”,以及确定分析缝宽和解决加速电压的稳定。得到注入系统分析磁铁的质量分辩率R_(10)~(-5)为66,高能分析磁铁的质量分辨率R_(10)~(?11)≥176。     

加速器质谱交替测量方法研究

加速器质谱技术由于其测量精度和灵敏度高等特点使其在多个学科得到广泛的应用。随着加速器质谱技术的改进,加速器质谱系统朝着小型化方向发展。本文在中国原子能科学研究院自主研发设计的端电压为300 kV的小型多核素加速器质谱系统的基础上,根据该设备的特点,研发了一套交替测量系统和交替测量方法,实现了对¹⁴C的准确测量。     

Accelerator Mass Spectrometry (AMS) 1977–1987

The eleventh Accelerator Mass Spectrometry (AMS 11) Conference took place in September 2008, the Thirtieth Anniversary of the first Conference. That occurred in 1978 after discoveries with nuclear physics accelerators in 1977. Since the first Conference there have now been ten further conferences on the development and applications of what has become known as AMS. This is the accepted acronym for the use of accelerators, together with nuclear and atomic physics techniques, to enhance the performance of mass spectrometers for the detection and measurement of rare long-lived radioactive elements such as radiocarbon. This paper gives an outline of the events that led to the first conference together with a brief account of the first four conferences before the introduction of the second generation of accelerator mass spectrometers at AMS 5.     

基于加速器质谱的尿中239Pu测量方法研究

239Pu作为一种长寿命极毒核素可通过吸入、食入和伤口渗入等途径进入人体,给工作人员造成内照射危害。目前一般采用尿样测量的方法评价职业人员内照射,现有尿中钚的测量手段有低本底α谱仪、热电离质谱仪、电感耦合等离子体质谱仪及加速器质谱仪等。加速器质谱对²³⁹Pu的测量可达更低的探测限,这对准确评价工作人员内照射剂量具有重要意义。利用中国原子能科学研究院自行研制的加速器质谱仪开展了尿中²³⁹Pu的前处理流程研究及²³⁹Pu高灵敏测量方法研究,方法检出限为1.1 μBq（0.47 fg）,该方法可为保障工作人员的辐射安全提供技术支持。