Speaker
Description
Dynamical fission calculations show that the post-scission configurations resemble two colinear pear-shaped fragments whose juxtaposed surface bulges subside relatively quickly, as the fragments acquire smoother shapes [1]. The associated rapid speed of the healing bulge surface may boost nucleons in the fragment to energies sufficient for emission. The present study explores this "catapult" mechanism proposed by Madler [2] by following the fate of nucleons that are reflected off the inwards moving bulge surface. Our simulations suggest that the mechanism may produce high-energy neutrons at the level of a few per cent with energies far in excess of typical evaporation neutrons. The calculations support the conclusion of Schulc et al. [3,4] that very energetic neutrons are emitted during fission, and their finding that the measured neutron spectrum dominates over the standard evaporation spectrum above ≈10 MeV.
[1] I. Abdurrahman, M. Kafker, A. Bulgac, and I. Stetcu, Neck Rupture and Scission Neutrons in Nuclear Fission, Phys. Rev. Lett. 132,242501 (2024).
[2] P. Madler, Catapult Mechanism for Fast Particle Emission in Fission and Heavy Ion Reactions, Z. Phys. A 321, 343 (1985)
[3] M. Schulc, M. Kostal, R. Capote, J. Simon, T. Czakoj, and E. Novak, Spectral averaged cross sections as a probe to a high energy tail of 235U PFNS, EPJ Web of Conf. 284, 04021 (2023).
[4] M. Schulc, M. Kostal, R. Capote, J. Simon, E. Novak, and T. Czakoj, High-energy neutron emission in thermal neutron-induced fission of 235U, Phys. Rev. C 109, 054616 (2024).
| Session | Nuclear Fission (prompt particle emission, fission yields) |
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