AMS measurement of In-situ produced cosmogenic 10Be in Loess Quartz in Luochuan

Loess is the most important and the most typical continental classic sediments of Quaternary. So the measurement of In-situ produced cosmogenic ¹⁰Be is expected to be used for the Loess stratigraphic age. But the production rate of In-situ produced cosmogenic ¹⁰Be in Loess quartz is very low. It requires very high sensitivity and accuracy of measurement. This work has measured the concentrations of ¹⁰Be of two layers in Loess section of Luochuan including L8, L9 and the concentrations of ¹⁰Be in (of) blank sample with the HI-13 AMS system at China Insitute of Atomic Energy(CIAE), then calculated the content of ¹⁰Be in loess quartz for each layer. The ratio of ¹⁰Be/⁹Be was found in the range of 10^－13. The background of ¹⁰Be/⁹Be was about 3×10^－14.     

Measurements of 79Se with AMS based on extracting molecular negative ions

A new method for measuring selenium-79 with AMS, which is based on extracting molecular negative ions, is described in this paper. According to the experimental results, the extraction ion form SeO₂^－ could depress the interference of Bromine-79 as much as 5 order levels, that is to say, the background of ⁷⁹Br can be deducted to ⁷⁹Br/Se≈10^－10. By the way, the chemical form of sample and preparation flow was also developed. Finally, three ⁷⁹Se AMS calibration standard samples with theoretical ⁷⁹Se/Se ratios of 5.06×10^－7, 6.87×10^－8, 5.40×10^－10 were obtained and the method of ⁷⁹Se measurement was set up, which actualized transmission and detection of ⁷⁹Se. By using our Bragg curve detector, the two isobars ⁷⁹Br and ⁷⁹Se could be partly identified to a certain extent and ⁷⁹Se can be identified from ⁷⁹Br about 1 order level. AMS measurements of the three calibration standard samples above were performed and good linearity was obtained. The sensitivity of the measurement is (5.16±1.80)×10^－11.     

Primary result of ^236U measurement with accelerator mass spectrometry at CIAE

The rare isotope ^236U has a half-life of 2.342（3）×107 years, and is produced principally by thermal neutron capture on ^235U. The isotopic atom ratio of ^236U/^238U depends on the integral thermal neutron flux received by the material of interest. ^236U is potentially useful as a ＂fingerprint＂ for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity. By extracting negative molecular ion UO^- from the uranium oxide target, simulating the ^236U^16O^- beam transport with ^238U^16O^- and ^208Pb2^16O^- pilot molecular ion beam, transporting the ^236U-containing ion beam with a high resolution injection magnet analyzer and electrostatic analyzer system, and finally identifying and detecting ^236U with a time-of-flight detector （TOF）, a method for AMS （Accelerator Mass Spectrometry） measurement of ^236U was established on the HI-13 Accelerator AMS system at China Institute of Atomic Energy.     

Primary result of ~(236)U measurement with accelerator mass spectrometry at CIAE

The rare isotope 236U has a half-life of 2.342(3)×107 years,and is produced principally by thermal neutron capture on 235U.The isotopic atom ratio of 236U/238U depends on the integral thermal neutron flux received by the material of interest.236U is potentially useful as a fingerprint for indicating the presence of neutron-irradiated uranium usually originating from nuclear activity.By extracting negative molecular ion UO- from the uranium oxide target,simulating the 236U16O- beam transport with 238U16O- an...     

A Bragg curve detector and its application in AMS measurements for medium-weight nuclides

The schematic layout and principle of a Bragg curve detector were showed in this paper. A Bragg curve detector was systemically modified and its performance was improved. The total energy resolution of the detector is 0.9% for alpha particle at energy of 5.48 MeV from ²⁴¹Am source, and the Bragg Peak resolution is 1.6%. Measurement of medium-weight nuclides by using the Bragg curve detector were carried at CIAE-AMS system. series of ³⁶Cl and ⁴¹Ca standard samples were measured. The results showed that this Bragg curve detector could clearly identify isobars ³⁶Cl-³⁶S and ⁴¹Ca-⁴¹K. The results also showed that the ΔZ/Z of 1/47, corresponding to Bragg Peak resolution is 2.1% at ion atomic number of about 16. The Bragg curve detector can be successfully used for AMS measurement.     

加速器质谱测量53Mn及其在地球科学中的应用

宇宙成因核素 53Mn是一种非常理想的地貌演变研究工具。近年来, 随着加速器质谱（AMS）技术的不断发展, 人们已能够进行53Mn的高灵敏测量。介绍了53Mn在地球科学中的应用前景、 国际研究现状及中国原子能科学研究院目前正在开展的53Mn高灵敏AMS测量方法的研究。The determination of cosmogenic 53Mn concentrations found in terrestrial formations has many interesting applications for Earth Sciences. With Accelerator Mass Spectrometry (AMS) it should be possible to detect minute amounts of 53Mn. The situation of international research of 53Mn AMS measurement and applications are presented. The AMS measurement method of 53Mn at China Institute of Atomic Energy and its applications prospect are to be explored.     

Progress in AMS Measurement of 182Hf at CIAE

Accelerator mass spectrometry （AMS） is one of the most promising methods to detect minute amounts of 182Hf. However, the sensitivity of 5×10^-11 for ^182Hf/180Hf obtained previously by the AMS method at China Institute of Atomic Energy （CIAE） cannot meet the requirement of some applications. We present some new improvements of measurement method for AMS measurement of 182Hf at the CIAE HI？13 tandem accelerator system. As a result, a sensitivity of 1.0×10^-11 for 182Hf/180Hf is achieved.     

Determination of the number of atoms of the long-lived nuclide 126Sn by γ-ray spectrometry

By using HPGe γ-ray spectrometry, the activity of the long-lived fission product 126Sn in a SnOB2 sample was measured. The number of 126Sn atoms and the ratio of 126Sn to Sn were calculated based on the half-life value of 2.35×105a and the chemical stoichiometry. The result of the ratio of 126Sn to Sn, （1.033±0.037）×10-8, is consistent with the results measured by the accelerator mass spectrometry （AMS） within uncertainty limits, which confirms our procedures in the measurement of 126Sn by AMS and lays a foundation for the AMS measurement of 126Sn at much lower levels.     

236U及其加速器质谱（AMS）测量

236U是一种长寿命放射性核素, 其半衰期为T_1/2=2.342(3)×107 a, 在自然界的含量极微, 天然铀中 236U/238U的原子比约为～10-14。 目前, 对于236U及其测量的研究报道较少。首先介绍了236U的产生, 并对地球中 236U的总量进行了估算。 概述了236U测定在亿年级中子注量率积分评估、 核环境和核活动监测, 以及地质学等领域中的重要应用。 最后,对国内外加速器质谱（AMS）测量236U的状况进行了综述,报道了中国原子能科学研究院AMS小组通过对同位素干扰鉴别的多方面研究, 初步建立了236UAMS测量方法。 236U is a longlived radionuclide with half life of 2.342(3)×107 a. The ratio of 236U/238U is about 10-14 in the natural Uranium. The origin and production of 236U in globe are introduced and estimated in this paper,respectively. The major applicationsion of 236U as a 100 million year neutron flux integrator,as a “fingerprint” for monitoring nuclear environment and nuclear activity,and as a tracer in geological studies are briefly summarized. The accelerator mass spectrometry(AMS) measurement of 236U in the world and the research on HI 13 tandem accelerator at China Institute of Atomic Energy(CIAE) is also mentioned in this paper.     

Developing AMS measurement of 59Ni at CIAE

Accelerator mass spectrometry (AMS) measurement of ⁵⁹Ni has been established at CIAE with the HI-13 tandem accelerator and the recently developed ΔE-Q3D detection system. ⁵⁹Ni standard and commercial NiO samples were measured to check the performance of the ΔE-Q3D detection system on ⁵⁹Ni isobar separation and suppression. An overall suppression factor of about 10⁷ for the interfering isobar ⁵⁹Co resulting in detection sensitivity as low as 3.8×10^-13 atomic ratio (⁵⁹Ni/Ni) has been obtained. Based on these techniques, the AMS measurement method of ⁵⁹Ni with high sensitivity is developed.