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

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

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

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

in-situ 3 He SEOP polarizer for Thermal neutrons

In this article, we describe a neutron polarizer for a new time-of-flight neutron spectrometer with the polarization analysis TOPAS. This instrument will use the convergent focused incoming beam of thermal neutrons with energies up to 150 meV (wavelength down to 0.74Å). The polarizer employs a high opacity 3He neutron spin filter with continuous 3He polarization provided by two laser array bars frequency narrowed by an ultra-compact volume Bragg grating. The system was successfully prototyped, and tested. In the course of first experimental test at the polarized hot neutron diffractometer POLI at MLZ, neutron polarization of 97.6% was achieved for 0.895Å neutrons and kept constant during 30 days