Bonn 2010 – wissenschaftliches Programm
HK 45.8: Vortrag
Donnerstag, 18. März 2010, 15:45–16:00, HG V
Detector system for hyperfine structure measurements at the Experimental Storage Ring (ESR) at GSI — •Denis Anielski1, Christopher Geppert2,3, Raphael Jöhren1, Volker Hannen1, Matthias Lochmann2,3, Rubén Lopéz Coto1, Wilfried Nörtershäuser2,3, Hans-Werner Ortjohann1, Rodolfo Sánchez3, and Christian Weinheimer1 — 1Institut für Kernphysik, Universität Münster — 2Institut für Kernchemie, Universität Mainz — 3GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt
Knowing the hyperfine transition of H- and Li-like heavy ions of the same isotope allows to test QED in extremely strong electromagnetic fields. While the transition energy of 209Bi82+ has been determined in previous laser spectroscopy experiments at the ESR, the transition in 209Bi80+ is challenging and still under investigation, because of the long transition wavelength (λ≈ 1555 nm) and a very low signal rate due to the long lifetime of the HFS state of 82 ms. At the ESR the wavelength can be Doppler-shifted to ≈ 640 nm in forward direction. To collect these forward emitted photons a detector setup has been developed. It consists of a movable parabolic-off-axis mirror, which will be positioned around the ion beam, and a very sensitive low noise PMT for detection of single photons. This talk will present the development and optimization of the setup with the simulation toolkit GEANT4. With the optimized system a signal rate of ≈ 45 Hz compared to ≈ 200 Hz background rate is expected. The mirror system is currently beeing manufactured and will be installed at the ESR next March. This work is supported by BMBF under contract number 06MS9152I.