AMS @ DREAMS
AMS Machine layout
Ions are extracted from two identical hybrid ion sources, which can handle gaseous and solid samples. Each Cs-sputter source is equipped with a 200-sample wheel. On the low-energy (LE) side the ions are separated by an energy-analyser, a 54° electrostatic deflector, and a mass-analyzer, a 90° magnet, equipped with a fast-bouncing system. The tandetron accelerator [Gottdang et al., 2002] contains a gas stripper and active stripper gas regulation. On the high-energy (HE) side, a 90° analysing magnet is followed by a Faraday-Cup for stable isotope measurements. The rare isotopes are detected by a 4-anode gas ionization chamber, after passing a 35° electrostatic deflector and a 30° vertical analysing magnet for further background reduction. For 10Be and 36Cl measurements a silicon nitride absorber foil (1 µm) can be inserted in the HE-part for post-stripping [Klein et al., 2008].
Chemical sample preparation
AMS measurements of long-lived radionuclides are only possible if samples are chemically treated, as the original samples (water, rocks etc.) that contain reasonable amounts of radionuclides are too big (100 g - 10 kg). Or in other words, the radionuclide concentrations in the range of sub-ppq are too low to allow an analysis of typical 1 mg-targets. Besides, the chemical separation is doing most of the work reducing the troublesome isobars, and eliminating possible contamination from other sources. For instance, the analysis of cosmogenic 10Be in quartz can only be performed if samples are previously cleaned from atmospherically-produced 10Be. The preparation of 10Be-, 26Al-, and 41Ca-AMS-targets needs the use of large quantities of hydrochloric acid (HCl) and, thus, should be preferably performed in a separated place than 36Cl- und 129I-AMS-target preparation keeping the risk of cross-contamination as low as possible. At DREAMS we have installed in autumn 2009 a dedicated lab for 36Cl and 129I sample preparation.
G. Rugel, S. Pavetich, S. Akhmadaliev, S.M. Enamorado Baez, A. Scharf, R. Ziegenrücker, S. Merchel, The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data, Nucl. Instr. and Meth. in Phys. Res. B 370 (2016) 94-100.
S. Merchel, S. Akhmadaliev, S. Pavetich, G. Rugel, Ungeduldige Forscher träumen mit DREAMS - Bestimmung langlebiger Radionuklide mit Beschleunigermassenspektrometrie, GIT Labor-Fachzeitschrift 56 (2012) 88-90.