Berlin 2005 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 6: Kern- und Teilchen-Astrophysik

HK 6.4: Vortrag

Freitag, 4. März 2005, 15:00–15:15, TU MA144

The European Recoil separator for Nuclear Astrophysics — •Daniel Schürmann — Institut für Experimentalphysik III, Ruhr-Universität Bochum, Universitätsstr. 150, 44780 Bochum

The fusion of Carbon and Helium in the nuclear reaction ¹²C(α,γ)¹⁶O takes place in the helium burning phase of red giant stars. This reaction is commonly refered to as a key reaction in nuclear astrophysics. Still the uncertainties of the astrophysical S(E) factor used in stellar model calculations are too large. To improve this situation we are performing a new measurement of the ¹²C(α,γ)¹⁶O cross section. Previous measurements are mainly based on the detection of the reaction gamma rays.

As a new tool for this research field the European Recoil separator for Nuclear Astrophysics (ERNA) was developed at the Dynamitron Tandem Laboratory of the Ruhr-Universität Bochum. In ERNA a ⁴He gas target is bombarded by a ¹²C ion beam. A combination of two Wien filters and a dipole magnet filters reaction products from beam particles. The oxygen recoils are then identified and detected freely, i.e. without the necessity of γ-ray coincidences. Such coincidences can be performed additionaly, resulting in background-free γ-ray spectra.

The talk will discuss key parameters of the separator, such as suppression and acceptance. The importance of knowledge about charge state distributions and charge exchange effects will be pointed out. First results will be shown on the ¹²C(α,γ)¹⁶O case and upcoming measurements of ³He(α,γ)⁷Be will be introduced. This project is supported by the Deutsche Forschungsgemeinschaft (RO 429/35-3).