Study of .sup.99Tc and .sup.129I measurement using 3MV Xi'an-AMS

• Published in: Journal of radioanalytical and nuclear chemistry Vol. 332; no. 4; p. 1253
• Main Authors: Fu, Yun-Chong, Zhang, Lu-Yuan, Bi, Yan-Ting, Liu, Qi, Cheng, Peng
• Format: Journal Article
• Language: English
• Published: Springer 01.04.2023
• Subjects: Comparative analysis; Ionization of gases; Measurement
• ISSN: 0236-5731; 1588-2780
• DOI: 10.1007/s10967-022-08757-5

The 3 MV AMS is completely unable to distinguish isobars within a gas ionization chamber for medium-heavy mass nuclides such as .sup.99Tc and .sup.129I. However, isobar suppression and elimination can be performed during the extraction stage in the ion source. Due to the limited energy in 3 MV AMS, .sup.99Tc and .sup.99Ru can't be separated, so it does not show sufficient advantages compared to ICP-MS. Therefore, .sup.99Tc analysis was rarely carried out using 3 MV or below AMS. In addition, .sup.99Tc as an artificial nuclide is confronted with no stable isotope for normalization. The .sup.129I was successfully analyzed by AMS due to the non-exitance of .sup.129Xe.sup.-. Xi'an-AMS is limited by hardware capabilities to only use a relatively inefficient + 5 charge state for measurement. In this work, the feasibility of .sup.99Tc analysis by 3 MV Xi'an-AMS was studied, and it was determined that .sup.93Nb molecules were used as the stable isotope for the normalization beam, carbides were used as the injected negative ions, and .sup.93Nb was used as the pilot beam. The transmission efficiency of the whole machine was tuned and optimized. .sup.99Tc correction with .sup.99Ru was discussed, and the detection limit of .sup.99Tc was estimated to be about ~ 10.sup.11 atoms in this preliminary work. Furthermore, the measurement of .sup.129I.sup.3+ was established at Xi'an-AMS, the interferences in the measurement of + 3 charge state were analyzed, and the measurement of .sup.129I.sup.3+ and .sup.129I.sup.5+ was compared using real samples and process blank samples. Both of them were consistent within 1[sigma], but the total efficiency of the + 3 charge state is about 1.75 times higher than that of the + 5 charge state.