Characterization of the isobar separator for anions integrated into the A. E. Lalonde laboratory's 3 MV AMS system

Accelerator Mass Spectrometry (AMS) of isotopes with abundant negative ion-forming isobars often requires the use of large accelerators to achieve high sensitivity measurements. The Isobar Separator for Anions (ISA) is a radio frequency quadrupole (RFQ) reaction cell system that can provide selective isobar suppression in the low energy system, prior to injection into an accelerator. A commercial version from Isobarex Corp. has been installed in a second injection line of the 3 MV tandem accelerator system at the A. E. Lalonde AMS Laboratory, University of Ottawa. Here, we present the characterization of the ISA for its optimization of S- suppression and Cl- transmission. He gas was selected as a cooling buffer gas, as it provided the best Cl- transmission of similar to 50 % through the ISA column. These tests use NO2 as a reaction gas due to its well-known exothermic reaction with S- but endothermic reaction with Cl-. More than six orders of magnitude reduction of S to Cl has been observed.

Automated summary

The Isobar Separator for Anions (ISA) is a system that allows for selective isobar suppression and transmission in low energy systems. By using helium gas as a cooling buffer and NO2 as a reaction gas, significant suppression of S- and transmission of Cl- can be achieved.