Right-left asymmetry of radiation from fission induced by polarised neutrons

Abstract

The effect of the right-left asymmetry is considered in the angular distribution of gamma quanta from fission of U-235 by polarised thermal neutrons, which depends on the polarisation of the neutrons with respect to the gamma-fission plane. Electric dipole radiation from fission fragments arising due to the Strutinsky-Denisov induced polarisation mechanism may give rise to such an effect. Earlier, this mechanism was shown to fit the non-statistical part observed in the gamma spectrum from spontaneous fission of Cf-252. The calculated value of the magnitude of the asymmetry parameter is on the level of 10${}^{-4}$. That is in agreement with the current experimental data. A crucial experiment to give a more definite picture of the concrete mechanism would be determination of the energy of the quanta responsible for the asymmetry. Detection of the quanta with the energy of ~5 MeV approaching the giant dipole resonance is needed in order to identify prompt gamma rays emitted at the stage of fissioning.

Comments: 12 pages, 1 figure. Delivered as an invited talk at the XLI PNPI Winter School on the Nuclear and Particle Physics, St. Petersburg, Repino, 19-24 February 2007; ISINN-2008, June 11-14, 2008, Dubna, Russia