Experimental Study of the (n,alpha) Reaction on a Set of Light Nuclei

An experimental setup based on an ionization chamber with Frisch grid and waveform digitizer was used for (n,a) cross section measurements. Use of digital signal processing allowed us to select a gaseous cell inside the sensitive area of the ionisation chamber with high accuracy. This kind of approach provides a powerful method to suppress background from detector components and parasitic reactions on the working gas. The new method is especially interesting for the study of reactions on elements for which solid target preparation is difficult (e.g. noble gases). Additionally it has the advantage of an accurate determination of the number of nonradioactive nuclei in the selected gas cell. In the present experiments a set of working gases was used, which contained admixtures of nitrogen, oxygen, neon, argon and boron. Fission of 238U was used as neutron flux monitor. The cross section of the (n,a) reaction for 16O, 14N, 20Ne, 36Ar, 40Ar and the branching ratio alpha0/alpha1 of the 10B(n,alpha0) to 10B(n,alpha1) reactions were measured for neutron energies between 1.5 and 7 MeV.JRC.D.5-Nuclear physic