Preprint / Nuclear Physics D15-2006-23 JINR-D15-2006-23

Experimental Research of the Radiative Capture of Thermal Neutrons in $^{3}$He

Abstract: A project of an experiment on measurement of the cross sections of radiative thermal neutron capture by $^{3}$He nuclei with production of one and two $\gamma$-quanta ($n_{\rm th}+^{3}$He $\to \alpha + \gamma$(2$\gamma$)) is presented. The interest in studying the processes is dictated by the following factors: a possibility of obtaining information on parameters of the nucleon $N$-$N$ potential and structure of exchange meson currents; a possibility of verifying the model of the mechanism for nucleon capture by the nucleus $^{3}$He in the low-energy region; necessity to solve some questions existing in astrophysics. The experiment is planned to be carried out on the PF1B beam of ILL reactor (Grenoble). The target is a hollow cylinder of pure aluminium ($\varnothing$140$\times$80~mm) filled with $^{3}$He and $^{4}$He (background experiment) at the pressure 2~atm. Registration of the $\gamma$-quanta is carried out by four BGO crystal ($\varnothing$100$\times$70~mm) detectors. According to the calculations the experiment, with 400-500 h of the PF1B beam running time, will allow cross sections for the above reactions to be measured for the first time with an accuracy of 2-4 {\%} (one-quantum process) and 7-10 {\%} (two-quantum process), which quite meets the purposes of the project.

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