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HK: Hadronen und Kerne

HK 51: Spectroscopy VIII, Fission

HK 51.8: Vortrag

Mittwoch, 18. März 1998, 15:45–16:00, E

The ²³⁸U(n,f) reaction — •F.-J. Hambsch¹, F. Vivès¹, S. Oberstedt², H. Bax¹, and G. Barreau³ — ¹JRC-IRMM, Retieseweg, B-2440 Geel, Belgium — ²ILL, F-38042 Grenoble, France — ³CENBG, F-2440 Bordeaux, France

The ²³⁸U(n,f) fission reaction has been studied at the 7 MV Van de Graaff accelerator of IRMM. Fission fragment detection was performed with a double Frisch-gridded ionization chamber at incident neutron energies ranging from 1.2 to 5.5 MeV. The experimental mass and TKE distribution have been compared to theoretical predictions [1] in the frame of the multi-modal random neck-rupture model of Brosa et al. [2]. A discontinuity in the mean TKE as a function of the incident neutron energy has been observed at about E_n = 3.5 MeV. This is about the energy above the barrier (E_n-E_B ∼ 2 MeV) needed to additionally break a proton pair. It is in line with observed changes in the number of prompt neutrons as a function of E_n [3]. The experimental results and the comparison with theoretical predictions will be presented and discussed.

[1] S. Oberstedt, F.-J. Hambsch and F. Vivès; Proc. Int. Symp. Large-Scale Collective Motion of Atomic Nuclei, Brolo, Italy, 15-19.10.1996.

[2] U. Brosa, S. Großmann and A. Müller; Physics Reports 197 (1990) 167

[3] J. Frehaut; NEANDC(E) 238/L (1986)