Bochum 1998 – scientific programme

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HK: Hadronen und Kerne

HK 51: Spectroscopy VIII, Fission

HK 51.6: Talk

Wednesday, March 18, 1998, 15:15–15:30, E

Parity-Nonconservation in nuclear fission — •A. K"otzle¹, F. G"onnenwein¹, P. Jesinger¹, G. Petrov², V. Petrova², A. Gagarski², O. Zimmer³, and V. Nesvizhevsky³ — ¹Physikalisches Institut, Universit"at T"ubingen , Auf der Morgenstelle 14, D-72076 T"ubingen — ²PNPI, Gatchina 188350, Russia — ³Institut Laue-Langevin, F-38042 Grenoble

Parity-nonconservation (PNC) in nuclear fission induced by polarized neutrons can be observed as an asymmetry of the fragment angular distribution relative to the direction of the neutron spin: W(θ) ∼ 1 + α_n^→f (n· p) . The aim of this work is to determine the mass- and energy dependence of the PNC-effect. One possible reason for such a dependence may be found in the different "‘valleys"’ of the potential surface, through which the fissioning nucleus descents from the saddle to the scission point (Brosa-modes). The results of this work should be a test of theoretical predictions connecting the size of the PNC-effect with the quantum-number K, the projection of the nuclear spin on the symmetry axis of the fissioning nucleus at scission.

In a new fourfold back-to-back ionization chamber about 5· 10⁹ fissions events have been observed in a first run on the cold beam of polarized neutrons at the high flux reactor of the ILL Grenoble. The experimental setup and first results are presented.