Technical Developments

Apart from research dedicated to different applications of accelerator mass spectrometry, we also work on new developments to improve the capabilities of the technique. Most of our current research on technical developments is related to the new compact AMS facility, HAMSTER, which will be installed at HZDR in 2023. Such developments are performed in collaboration with the departments of Instrumentation (FWFI) and Mechanical Engineering (FWFM) at HZDR, the group of Isotope Physics of the University of Vienna, and National Electrostatic Corp. (NEC). Some of the research lines of the group related to technical developments are:

  • The design of new beamline elements for the optimization of ion beam transport.
  • The programming of software for automated tuning and measurement.
  • The design of the new laser-based isobar suppressor, ILTIS (Ion Linear Trap for Isobar Suppression), which will be installed in the HAMSTER facility.
  • The application of laser-based isobar suppression via the instrument ILTIS (Ion Linear Trap for Isobar Suppression) to the measurement of new AMS radionuclides.
Isobar suppression by selective laser photodetachment
Foto: Principle of laser photodetachment ©Copyright: Dr. Johannes Lachner

Basic principle of laser photodetachment. The isobar will be suppressed if the energy of the photons is higher than the EA of the isobar and lower than the EA of the radionuclide.

While isobar suppression techniques for AMS typically used in the past rely on reaching relatively high energies, of at least 0.1 MeV/u, laser photodetachment is a technique than is applied in the pre-accelerator sector of the system. The main advantage of this technique, therefore, is that it can be applied to any AMS facility, no matter the terminal voltage of the accelerator. The technique is based on the threshold character of the laser photodetachment of electrons: a negative ion will lose its extra electron, and thus become neutral, when a photon with an energy higher or equal to its electron affinity (EA) interacts with it. If a the negative ion of interest (atomic or molecular) has a higher EA for the AMS radionuclide in comparison to its stable isobar, photons with an energy between these two EA’s would neutralize ions of the stable isobar while not affecting the ion of interest.

Such an interaction takes place in an "ion cooler", where molecular and atomic anions are slowed down to kinetic energies of few 10 eVs and are guided through a linear Paul-trap, a buffer gas filled radiofrequency quadrupole. The interaction with the buffer gas further slows down the ions. This way, one reaches interaction times of several milliseconds for the ions with photons of a collinearly injected laser beam. Examples of some ion pairs where the technique has shown optimal results are 26AlO- (EA=2.6 eV) vs. 26MgO- (EA=1.63 eV), and 36Cl- (EA=3.6 eV) vs. 36S- (EA=2.1 eV). Actually, such a technique is already being used for the routine measurements of 26Al and 36Cl at the VERA facility at the University of Vienna.

At HZDR, a second-generation laser-based isobar suppressor, ILTIS, is being designed, and will be tested in our Teststand system. ILTIS will be finally moved to the new compact AMS facility, HAMSTER, when it is installed in 2023. The AMS group at HZDR is also working, in collaboration with the group of Isotope Phyics of the University of Vienna, in the optimization of laser‑based isobar suppression for the AMS measurements of some radionuclides, like 41Ca (using the CaF3- ion), 135,137Cs (using the CsF2- ion), and 59Ni (using the Ni- ion). We are studying also different possibilities of negative ions for the application of this technique to measure other AMS radionuclides, such as 53Mn.

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Further Reading

  • Forstner, O., Andersson, P., Diehl C., Golser, R., Hanstorp, D., Kutschera, W., Lindahl, A., Priller, A., Steier, P. and Wallner, A. (2008). Isobar suppression in AMS using laser photodetachment. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 266, 4565-4568. https://doi.org/10.1016/j.nimb.2008.05.080
  • Martschini, M., Pitters, J., Moreau, T., Andersson, P., Forstnera, P., Hanstorp, D., Lachner, J., Liu, Y., Priller, A., Steier, P. and Golser, R. (2017). Selective laser photodetachment of intense atomic and molecular negative ion beams with the ILIAS RFQ ion beam cooler. International Journal of Mass Spectrometry, 415, 9–17. https://doi.org/10.1016/j.ijms.2016.12.015
  • Martschini, M., Hanstorp, D., Lachner, J., Marek, C., Priller, A., Steier, P., Wasserburger, P. and Golser, R. (2019). The ILIAMS project—An RFQ ion beam cooler for selective laser photodetachment at VERA. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 456, 213-217. https://doi.org/10.1016/j.nimb.2019.04.039
  • Martschini, M., Lachner, J., Hain, K., Kern, M., Marchhart, O., Pitters, J., Priller, A., Steier, P., Wiederin, A., Wieser, A. and Golser, R. (2021). 5 years of ion-laser interaction mass spectrometry-status and prospects of isobar suppression in AMS by lasers. Radiocarbon, FirstView, 1-14. https://doi.org/10.1017/RDC.2021.73
  • Lachner, J., Marek, M., Martschini, M., Priller, A., Steier, P. and Golser, R. (2019). 36Cl in a new light: AMS measurements assisted by ion-laser interaction. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 456, 163-168. https://doi.org/10.1016/j.nimb.2019.05.061
  • Lachner, J., Martschini, M., Kalb, A., Kern, M., Marchhart, O., Plasser, F., Priller, A., Steier, P., Wieser, A. and Golser, R. (2021). Highly sensitive 26Al measurements by Ion-Laser-InterAction Mass Spectrometry. International Journal of Mass Spectrometry, 465, 116576. https://doi.org/10.1016/j.ijms.2021.116576