The AMS Measurement Of ¹⁰Be And ²⁶Al With High Sensitivity And High Precision

The study for in-situ produced cosmogenic nuclides,especially ¹⁰Be and ²⁶Al,which are the long-lived radionuclides produced by secondary cosmic ray has been developed rapidly with the development of AMS.However,it's hard for the further studies because of the measurement sensitivity.The measurement method with high sensitivity and high accuracy for ¹⁰Be has been developed in the CIAE-AMS system in this work.(1)After choosing suitable conducting medium and suitable ratio of sample to conducting material,the beam current of BeO^-is 3 times increased,now,the typical current is about 1.5μA.(2)In order to improve the measurement precision,simultaneous measurement system and method were established,and the simultaneous measurement method was successfully used in the AMS measurement to reduce the error due to the fluctuation of the beam current.(3)To improve the measurement sensitivity,the entrance window of ionization chamber has been improved,and a data processing software was used to remove the interference of ¹⁰B and ⁷Be by gating on 4 signals.After that,the background of n_(10Be)/n_(9Be)has reduced from 9.6×10^-14to 1.7×10^-14.(4)A series of standard samples are prepared and measured,these standard sample are useful for the measurement of the samples with low concentrations of ¹⁰Be.(5)Chemical processes which used to extract Be and Al from the loess quartz in Luochuan have also been developed successfully.(6)The concentrations of ¹⁰Be extracted from four stratums of Luochuan including L1,L2,L4,L8 were measured.The content of ¹⁰Be in these loess were about 10⁶ at·g^-1.The measurement of in-situ produced cosmogenic ¹⁰Be and ²⁶Al in loess quartz would confirm the value of ¹⁰Be/²⁶Al which can be used to determine the loess stratum age.It is the first time to determine the buried age of the Chinese Loess using in-situ produced cosmogenic nuclides.Another work of the ²⁶Al measurement has also been explored in this paper.The measurement method for extracting Al^-and AlO^-were tested.A method for measurement of ²⁶Al by using gas filled magnet combined with TOF was also introduced.This method will be used for 26Al in near future.