UW, Warsaw

How many fusion barriers?

L.Swiderski, P.Czosnyka, M.Kowalczyk, E.Piasecki, K.Piasecki, M.Witecki
Institute of Experimental Physics, Warsaw University, Poland

K.Hagino
Kyoto University, Japan

J.Jastrzebski, A.Kordyasz, M.Kisielinski
Heavy Ion Laboratory, Warsaw University, Poland

T.Krogulski
Institute of Experimental Physics, University of Bialystok, Poland

M.Mutterer
Institut fur Kernphysik, Technische Universitat, Darmstadt, Germany

N.Rowley
Institut de Recherches Subatomique, Strasbourg, France

W.Trzaska
University of Jyvaskila, Finland

The height of barrier for fusion of two colliding nuclei is roughly proportional to the product of their atomic numbers Z1Z2. However, it is known that fusion depends also on the structure of colliding nuclei. This fact leads to distribution of fusion barrier heights, which is sometimes clearly structured. As it has already been shown by Timmers et al. [1], one can extract fusion barrier distribution by measuring quasi-elastic scattering cross-sections at backward angles using the following formulae:

D_qel=d/dE qel/Rut

Such experiments are demanding in relation to beam energy resolution and energy steps control. Therefore measurements of these kinds are usually performed using tandem accelerators, which unfortunately do not allow accelerate ions of noble gases. To solve this problem we have developed a method to measure fusion barrier distributions by means of cyclotron. Using the Warsaw Cyclotron beam and experimental set-up described inr our previous work [2], we have extracted barrier distributions for 20Ne + 112,116,118Sn systems. Results were compared to coupled-channels calculations performed using the CCFULL code. Puzzling disagreement between experiment and theory is observed.

References:

[1] H.Timmers et al., A584 (1995) 190
[2] E.Piasecki et al., Phys. Rev. C 65 (2002) 054611

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