基于小型单极加速器质谱测量~(14)C的样品制备技术研究

为满足新研发的200kV单极静电加速器质谱仪测量14 C的需要,开展了14 C样品制备技术研究。在自主设计的14C制样装置上优化了H2-Fe法、Zn-Fe法、Zn-H-Fe法制备石墨样品的实验条件,制备的样品经离子源引出12C-的束流均可达15~40μA,稳定性好于0.2%。在加速器质谱仪的调试中发现压低制备样品12CH+13C和12C的粒子个数比更有利于实现14 C-SE-AMS小型化及高灵敏测量。~(14)C-SE-AMS的测试样品中碳含量小于1mg时,采用Zn-Fe法有利于压低~(12)CH+~(13)C和~(12)C的粒子个数比;样品碳含量为1~5mg时,采用Zn-Fe法和Zn-H-Fe法效果相当。建立的制样方法对含碳量为100μg~5mg的样品,其产率均能达到95%以上,且空白样品测试结果表明此系统能有效避免样品制备中的交叉污染。

14 C Sample Preparation for Compact Single Stage AMS

In order to satisfy 14 C measurement with the new developed 200 kV single stage electrostatic accelerator mass spectrometer,the sample preparation processes for 14 C were investigated.The graphitization experimental conditions for H 2-Fe,Zn-Fe and Zn-H-Fe methods were optimized on self-designed 14 C sample preparation system.The beam current of 12 C- for all prepared samples can reach 15-40 μA and its stability is bet-ter than 0.2%.The 14 C measurement shows that the lower particle number ratio of 12 CH+13 C and 12 C benefits the high sensitivity and miniaturization of device.The result also shows that the Zn-Fe method can depress the particle number ratio of 12 CH + 13 C and 12 C for the samples with the carbon content less than 1 mg,while,for the carbon content among 1 mg to 5 mg,the Zn-Fe and Zn-H-Fe methods have the equivalent effect.For above preparation methods,the yield of carbon can reach more than 95% for the carbon content of 100 μg-5 mg.Moreover,through blank sample measurement it is proved that the cross contamination during the sample preparation can be avoided.