AMS of 90Sr at the sub-fg-level using laser photodetachment at VERA


AMS of 90Sr at the sub-fg-level using laser photodetachment at VERA

Marchhart, O.; Martschini, M.; Honda, M.; Hanstorp, D.; Lachner, J.; Liang, H.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

The fission product 90Sr (T1/2 = 28.9 a) is of interest in environmental sciences for its radiotoxicity as well as a potential tracer. Limits of detection (LoD) of mass spectrometric methods such as ICP-MS, RIMS or conventional AMS are close to the radiometric limit of 3 mBq.
The main problem in AMS of 90Sr is the strong interference of the stable isobar 90Zr. This problem can be overcome with the new Ion Laser InterAction Mass Spectrometry (ILIAMS) setup at the Vienna Environmental Research Accelerator (VERA). It provides near complete suppression of elemental or molecular isobars via selective laser photodetachment inside a gas-filled radiofrequency quadrupole (RFQ). With 10W of laser power from a 532nm cw-laser and a He+O2 mixture as buffer gas, ILIAMS achieves a suppression factor for 90Zr of 10⁷. Extracting SrF₃^− out of the ion source and elemental separation inside an ionization chamber gives an additional Zr suppression of 10⁵.
Measurements with dilution series of reference materials were successfully conducted. The overall Sr detection efficiency is 0.4 %₀ and the
blank level 90Sr/Sr=(4.5 ± 3.2)×10^−15. This corresponds to a more than tenfold improved LoD of 0.1 mBq.

Permalink: https://www.hzdr.de/publications/Publ-30218
Publ.-Id: 30218