【摘要】 为满足41Ca生物示踪样品测量的需要,在北京HI-13串列加速器质谱(Accelerator Mass Spec- trometry,AMS)系统上建立了以CaF2为靶样的41Ca AMS分析方法.生物样品和41Ca标准样品经过化学分离和纯化,制备成CaF2作为靶物质,AMS测量41Ca时,离子源引出CaF3-负离子,膜剥离后的电荷态选择为7+态,加速器端电压选定为8.5MV,用充有140mbarP10气体的多阳极电离室探测41Ca.结果显示探测器可实现对41Ca与同量异位素干扰41K的分辨,粒子谱中41K的计数率很低,对41Ca不形成干扰.对制备的4个标准样品(41Ca/40Ca在1.785×10-8-1.750×10-10范围)的测量结果显示41Ca/40Ca绝对测量值与标称值之间的线性关系良好(r2=0.997),经41Ca/40Ca为1.785×10-8的标准样品归一化后,S2,S4两个标样的测量值与标称值吻合较好,但标样S3的测量值与标称值有较大偏离.估计生物样品的41Ca/40Ca本底值低于8.2×10-13.更多还原

【Abstract】 For determining numbers of 41Ca labeled biological samples, the analytical method of 41Ca/40Ca by Accelerator Mass Spectrometry (AMS) using CaF2 target was developed at the Beijing HI-13 AMS system. 41Ca in the biological samples and 41Ca standard samples were prepared to CaF2 with a more effective chemical separation and purification procedure. In the 41Ca AMS measurement, CaF3- negative ion was extracted from ion resource, 7+ charge state of particles was chosen after carbon foil stripping and accelerated at 8.5MV terminal voltage. 41Ca ions were finally recorded by an 140mbar P10 gas filled multi-anode ionization chamber detector. The results showed that 41 Ca and the main isobar, 41K could be clearly identified in the two-dimensional density spectra, and the interference of 41K to 41Ca was eliminated with the very low 41K counting rate. The absolute measured values of 4 standard samples with 41Ca/40Ca in the range of 1.785 × 10-8-1.750×10-10 were in good linear relationship with the standard values (r2 = 0.997). After normalized with the 1.785×10-841Ca/40Ca standard, the measured values of S2 and S4 standard samples were in good agreement with the nominal values, however, the measured value of S3 deviated the nominal value largely. The 41Ca/40Ca of the biological blanks were estimated below 8.2×10-13.更多还原