Super-SIMS (SIMS = Secondary ion mass spectrometry) is an ultrasensitive analytical method for the determination of stable elements at the ultratrace level. The HZDR Ion Beam Center developed the set-up by coupling a conventional SIMS to a 6 MV tandem accelerator.
The Department Accelerator Mass Spectrometry and Isotope Research at the Institute of Ion Beam Physics and Materials Research currently operates the instrument. Measurement tasks and the further development of the equipment are defined in close coordination with the Helmholtz Institute Freiberg for Resource Technology. The device is operated in beam times. The application is done via HZDR-GATE portal.
How does it work? ►
A sputter source is used to focus a Cs+-beam onto a very flat and well polished sample surface. The extracted negative ions (elements or molecules) are electrostatically and magnetically separated. A first isobar suppression is gained right in the ion source, unless they form any negative ions (e.g. no formation of Mg- when analyzing Al).
Ions with the correct energy, mass and charge are injected into the 6 MV accelerator and accelerated to the positively charged high-voltage terminal. Negative ions are passing an area filled with argon gas, thus, losing electrons from the outer shell. Thereby, all existing molecules are destroyed. The henceforth multiple-positively charged ions are accelerated a second time in the direction of the other end of the accelerator.
At the so-called high-energy site all ions are again magnetically and electrostatically separated before they are finally detected by Faraday-Cups (major elements) or gas ionization detectors (trace elements).
Basic Literature ►
- S. Matteson, Issues and opportunities in accelerator mass spectrometry for stable isotopes, Mass Spectrometry Reviews 27 (2008) 470-484
- E. J. von Wartburg, Messung von Isotopenverhältnissen stabiler Spurenelemente mit Beschleuniger-Sekundärionen-Massenspektrometrie, Dissertation, ETH Zürich (2007).
- E.E. Groopman et al. Rapid, molecule-free, in situ rare earth element abundances by SIMS-SSAMS, Journal of Analytical Atomic Spectrometry, 32 (2017) 2153 - 2163