Study of mixing ratios of isotopes ⁵⁶Fe and ⁵⁷Fe by nuclear orientation techniques with PolarEx

This study focuses on the Low Temperature Nuclear Orientation method (LTNO). This method relies on the interactions of nuclear magnetic moments with electromagnetic fields. These interactions may induce a spontaneous orientation of nuclear spins if the temperatures are very low -much lower than 1 K- and if the magnetic fields are intense enough -several tens of Tesla. As a result of this orientation, the emission of the nucleus is anisotropic and in general this anisotropy is the observable of LTNO experiments. As one can guess, LTNO physics is a challenging field from the experimental point of view, but that is why it is also so attractive. The goal of this study is to extract from LTNO measurements the mixing ratios δ of ⁵⁶Fe and ⁵⁷Fe transitions, which are the relative mixing of electromagnetic multipolarities. The study of these mixing ratios is a key to constrain nuclear models. In addition, a study of summing processes in nuclear orientation experiment has been made through simulation. The apparatus used in this work is PolarEx (Polarization of Exotic nuclei) which is an experimental installation for on-line nuclear orientation experiment which is being installed at ALTO. It was tested off-line in 2014, first to test the cryogenic apparatus, and then to make a commissioning experiment. This experiment was performed with a source of ^56,57,58Co and ⁵⁴Mn, and shows good results which confirmed that PolarEx is ready to be installed on-line. (author)