Applications of a compact ionization chamber in AMS at energies below 1 MeV/amu

✍ Scribed by O. Forstner; L. Michlmayr; M. Auer; R. Golser; W. Kutschera; A. Priller; P. Steier; A. Wallner

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 408 KB
• Volume: 266
• Category: Article
• ISSN: 0168-583X
• DOI: 10.1016/j.nimb.2008.02.060

✦ Synopsis

The increasing demand for measuring long-lived radionuclides with small AMS machines at energies below 1 MeV per nucleon raises the need for compact detectors which still have a decent energy resolution and allow for a clear identification of the incident particles. Based on a design by the AMS group at the ETH Zurich a compact gas ionization chamber was built and installed at the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator). The main challenge in AMS is the detection of rare isotope species in the presence of strong isotopic and isobaric interferences. The task of the ionization chamber is the suppression of the unwanted isobar by separating the ions via their different stopping powers. Measurements of 36 Cl at VERA showed an achieved suppression of the unwanted stable isobar 36 S of 3 Â 10 À4 and measurements of 10 Be showed an achieved suppression of 10 B of at least 3 Â 10 À6 . Additional suppression of the isobaric ions can be achieved by a degrader foil technique applied to 10 Be measurements by G.M. Raisbeck. In combination with the new ionization chamber the achieved suppression of 10 B is at least 10 À10 . Measurements of blank samples at VERA show that the background for AMS with 10 Be is below 2 Â 10 À15 .