Speaker
Ryan Bolen
(University of Ottawa)
Description
Caesium sputtered ion sources when used on solid graphite powdered samples have been thus far - capable of generating a peak negative (_6^12)C-beam current of around 200-400 µA (~〖10〗^15 ions/s). However, when using CO2 gas directly as the carbon source – less of the sample is lost during the graphitization process, which is of vital importance when one has a limited amount of the material they want to analyze. Middleton (1984) tested a Cs sputtering ion source to form C - – ions directly from CO2 gas on titanium targets. At which time he produced a 10 µA beam current by using a very low CO2 flow rate of <4 µL/min. (STP) (<2 µg/min. carbon) that was shown to be the best for high sputtering efficiencies of ~10%. Accordingly, the runtime was longer – but more of the carbon ions were measured. In comparison, when using TiH2 & other solid hydride samples were used to create a negative hydrogen beam (using a similar source as mentioned above), an 80-90 µA peak current was the maximum ever achieved (while 20-30 µA is typical). This report describes the development of novel gas source AMS - to ideally be able to measure tritium ions & other rare isotopes using µg sample sizes.
Author
Ryan Bolen
(University of Ottawa)
