Mainz 2026 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 8: Isobar Suppression Techniques

MS 8.6: Talk

Friday, March 6, 2026, 12:30–12:45, N 6

A compact AMS laser photo-detachment system for isobar suppression — •Lauren Bezzina, Christof Vockenhuber, Marcus Christl, Philip Gautschi, Lukas Wacker, Urs Ramsperger, Arnold Müller, and Thorben Wulff — Labor für Ionenstrahlphysik (LIP), Otto-Stern-Weg 5, 8093 Zürich, Switzerland

Compact accelerator mass spectrometry (AMS) systems have advanced significantly in recent years, yet effective isobar suppression for nuclides such as 36Cl at the 200 kV scale remains a major challenge. To address this, we are implementing a laser photo-detachment scheme that selectively neutralises interfering anions while preserving the radionuclide of interest. This approach requires decelerating the ion beam to sub-eV energies to maximise laser-ion interaction, typically achieved using a radiofrequency quadrupole (RFQ) cooler operated with a light buffer gas. The suppression stage will be integrated into a recommissioned 200 kV MICADAS-type accelerator. The upgraded system, named MI-Q, will be the first compact AMS instrument to incorporate a laser-based isobar suppression stage.

We present the design and optimisation of the MI-Q low-energy section, comprising the deceleration optics and RFQ cooler. A multi-electrode deceleration lens is being developed to provide tunable potential gradients, enabling precise control of sub-eV beam transport into the gas cell. The RFQ incorporates guide electrodes that generate the axial DC drag field needed to transport ions through the cooler while maintaining transverse confinement. Fabrication of the key components is underway, with thorough commissioning planned.