Berlin 2005 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 17: Kernphysik/Spektroskopie
HK 17.6: Vortrag
Montag, 7. März 2005, 15:30–15:45, TU MA004
Measurement of beam contamination at the REX-ISOLDE radioactive beam accelerator — •Vinzenz Bildstein — Max-Planck-Institut für Kernphysik, Heidelberg, Germany
Due to the production and acceleration method for radioactive ions at REX-ISOLDE[1] there are three sources for beam contaminations: The first source is a direct isobaric contamination as the general purpose mass separator of ISOLDE is not able to separate different isobars (e.g. 30Mg and 30Al). Second when the ions are captured in the REX-trap and charge bred in the EBIS part of them may β-decay also resulting in an isobaric contamination of the beam (e.g. during 30 ms of trapping and breeding of 30Mg 6.0 % of it will decay to 30Al). Finally, the beam may contain stable contaminants from the residual gas in the REXEBIS if their mass to charge ratio allows them to pass the mass separator of REX, wich has a resolution of Δ (A/q)/(A/q) < 1/100 [1] (e.g. 30Mg8+ and 15N4+ or 32Mg9+ and 32S9+).
Besides trying to reduce these contaminants it is important to identify the contaminants qualitatively and quantitatively. One possibility for ions with Z below about 20 is to measure their specific energy loss using a thin silicon detector. In September 2004 two 10 µm thick silicon pin-diodes were installed at the MINIBALL setup in order to determine the beam contaminations of neutron rich Mg beams continuously. Sources of contamination and the results of these measurements will be discussed.
[1] Accelerated radioactive beams from REX-ISOLDE, O. Kester et. al, Nucl. Instr. and Meth. in Phys. Res. B 204 (2003) 20-30