Stuttgart 2012 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 9: Accelerator Mass Spectrometry and Applications II
MS 9.5: Vortrag
Freitag, 16. März 2012, 11:30–11:45, V57.06
Investigations of the sputtering process in Middleton type ion sources — •Martin Martschini1, Pontus Andersson1, Oliver Forstner1, Robin Golser1, Dag Hanstorp2, Anton O. Lindahl2, and Johan Rohlén2 — 1University of Vienna, Faculty of Physics - Isotope Research, VERA Laboratory, Vienna, Austria — 2University of Gothenburg, Gothenburg, Sweden
Since 1977, sputter ion sources of the Middleton type have been the main tool used to create stable, intense negative ion beams for injection into AMS machines. Nevertheless, the theory behind negative ion formation is not fully agreed upon. As part of the work in trying to unravel the mechanisms of hard sputtering in a cesium rich environment, we have resolved the spectrum of blue light emitted from the cathode region during high current output. A fiber coupled spectrometer was used to detect light in the wavelength region 200 to 1100 nm. The spectrum showed that the emitted light consists almost entirely of persistent lines from neutral cesium and no persistent lines from other species or charge states such as Cs+ were observed.
In another experiment, the surprising effect of continuous wave laser light directed onto the cathode surface was studied. The laser light induced a significant change in oxygen, sulfur and chlorine negative ion production from a AgCl target. Independent from laser wavelength, ∼100 mW of laser light changed the elemental composition of the ion beam by up to one order of magnitude. This technique was successfully applied during a regular AMS measurement of 36Cl at VERA. However, the physics behind the effect requires further investigations.