M. Mutterer

Experimental Studies of Nuclear Fission Dynamics Near the Scission Point

Conditions for formation of angular and energy distributions of light particles emitted in ternary fission of 233, 235U, 239Pu, and 245Cm nuclei induced by cold polarized neutrons have been studied in the course of investigating T-odd asymmetry in emission of these particles with respect to the plane formed by the fission axis and the polarization axis of the fissioning nucleus. The results obtained lead to the conclusion that in ternary fission charged particles are emitted by the fissioning nuclear system rotating around the polarization direction.

Searching for Rare Decay Modes in the Reaction 238U+4He (40 MeV)

In the present paper we describe an experiment performed on the reaction 238U + 4He (40 MeV) using a two‐arm TOF‐E (time‐of‐flight vs. energy) spectrometer with micro‐ channel plate detectors and mosaics of PIN diodes. This experiment has aimed at searching for fine structures in the total kinetic energy vs. fragment mass (TKE ‐ M) distributions of binary events, and disclosing rare ternary decay modes others than already known from ternary fission. Details of the procedures of data handling are briefly described as well.

Rotation of scissioning nuclei observed in ternary fission induced by polarized neutrons

Angular distributions of light charged particles relative to the momentum of the light fission fragment were studied in ternary fission induced by cold polarized neutrons. It was discovered that the angular distribution is asymmetric with respect to a plane determined by the direction of incident neutron spin and the light fragment momentum. The violation of the mirrorlike symmetry was established at the level of ∼10−2–10−4 for three reactions studied: 233U(n,f), 235U(n,f) and 239Pu(n,f). In spite of the smallness of the effects the neutron spin flip method allowed to make reliable measurements. The current status of the experimental studies of the effect and its interpretation are presented. Perspectives for further studies of the new phenomenon are discussed.

Fine structure in fragment mass-energy distribution from 238U+40Ar (275 MeV)

Existence of a new feature in fragment mass-energy distribution is reported. Careful analysis of the data obtained in the reaction 238U + 40Ar (275 MeV) shows that small but statistically significant ripples visible already in the gross mass spectrum come from extended and regular 2D patterns in the TKE vs. mass matrix. Intensity distributions of these patterns coincide with the location of heavy clusters such as 78Ni, 108Mo, or 132Sn. Presumably, the observed patterns show the dominant trajectories in the elongation vs. mass-asymmetry space of the decaying system. This information, unknown in the past, can shed a new light even on the previously well-studied reactions.