title: Light induced suppression of sulfur in a cesium sputter ion source.
abstract: New techniques for suppression of atomic isobars in negative ion beams are of great interest for accelerator mass spectrometry (AMS). Especially small and medium-sized facilities can significantly extend their measurement capabilities to new interesting isotopes with a technique independent of terminal voltage. In a new approach, the effect of continuous wave laser light directed towards the cathode surface in a cesium sputter ion source of the Middleton type was studied. The laser light induced a significant change in oxygen, sulfur and chlorine negative ion production from a AgCl target. Approximately 100 mW of laser light reduced the sulfur to chlorine ratio by one order of magnitude. The effect was found to depend on laser power and ion source parameters but not on the laser wavelength. The time constant of the effect varied from a few seconds up to several minutes. Experiments were first performed at the ion beam facility GUNILLA at University of Gothenburg with macroscopic amounts of sulfur. The results were then reproduced at the VERA AMS facility with chemically cleaned AgCl targets containing ∼1 ppm sulfur. The physical explanation behind the effect is still unclear. Nevertheless, the technique has been successfully applied during a regular AMS measurement of36Cl.
authors.affiliation: University of Vienna, Faculty of Physics - Isotope Research, VERA Laboratory, Währinger Straße 17, A-1090 Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Martschini
authors.forename: Johan
authors.initials: J
authors.lastname: Rohlén
authors.forename: Pontus
authors.initials: P
authors.lastname: Andersson
authors.forename: Robin
authors.initials: R
authors.lastname: Golser
authors.forename: Dag
authors.initials: D
authors.lastname: Hanstorp
authors.forename: Anton O
authors.initials: AO
authors.lastname: Lindahl
authors.forename: Alfred
authors.initials: A
authors.lastname: Priller
authors.forename: Peter
authors.initials: P
authors.lastname: Steier
authors.forename: Oliver
authors.initials: O
authors.lastname: Forstner
keywords: AMS; Cesium sputter negative ion source; Laser induced isobar suppression; Sulfur vs. chlorine production