Measurement of the ROT effect in the neutron induced fission of ²³⁵U in the 0.3 eV resonance at a hot source of polarized neutrons

¹ Joint Institute for Nuclear Research, 141980 Dubna, Russia
² Institute for Theoretical and Experimental Physics of National Research Centre “Kurchatov Institute”, 117218 Moscow, Russia
³ Petersburg Nuclear Physics Institute of National Research Centre “Kurchatov Institute”, 188300 Gatchina, Russia
⁴ Institut für Kristallographie, RWTH Aachen and Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum (MLZ), Lichtenbergstr. 1, 85748 Garching, Germany
⁵ Forschungs-Neutronenquelle Heinz Maier-Leibnitz, 85747 Garching, Germany
⁶ National Nuclear Research Centre, Baku, Azerbaijan
⁷ Institute of Nuclear Physics of the National Nuclear Center of Kazakhstan, 050032 Almaty, Kazakhstan

^* e-mail: kopatch@nf.jinr.ru

Published online: 6 March 2018

Abstract

The TRI and ROT asymmetries in fission of heavy nuclei have been extensively studied during more than a decade. The effects were first discovered in the ternary fission in a series of experiments performed at the ILL reactor (Grenoble) by a collaboration of Russian and European institutes, and were carefully measured for a number of fissioning nuclei. Later on, the ROT effect has been observed in the emission of prompt gamma rays and neutrons in fission of ²³⁵U and ²³³U, although its value was an order of magnitude smaller than in the α-particle emission from ternary fission. All experiments performed so far are done with cold polarized neutrons, what assumes a mixture of several spin states, the weights of these states being not well known. The present paper describes the first attempt to get “clean” data by performing the measurement of gamma and neutron asymmetries in an isolated resonance of ²³⁵U at the POLI instrument of the FRM2 reactor in Garching.