In a set of ${\mathrm{B}}^{10}$-loaded C-2 emulsions exposed to eight neutron energies in the range 6-20 Mev, 1541 three-prong stars were found which were caused by either the ${\mathrm{B}}^{10}(n, t2\mathrm{}\alpha )$ or the ${\mathrm{B}}^{10}(n, d{n}^{\prime }2\alpha )$ reaction. The triton cross section at 14 Mev is 102±17 mb and decreases with increasing bombarding energy, while the deuteron cross section is 128±19 mb and increases slightly with energy. The triton reaction proceeds partially through the 4.61-Mev state in ${\mathrm{Li}}^7$ and partially as a three-body breakup. In the deuteron reaction the following intermediate nuclei are formed: ${\mathrm{Be}}^9$, 2.43-Mev state; ${\mathrm{Be}}^8$, ground state and possibly the 2.9-Mev level; ${\mathrm{Li}}^7$, 10.8- and 12.4-Mev levels; and ${\mathrm{Li}}^6$, 2.19-Mev level. Four examples were found of the ${\mathrm{N}}^{14}(n, t3\mathrm{}\alpha )$ reaction. The feasibility of using the ${\mathrm{B}}^{10}(n, t2\mathrm{}\alpha )$ reaction as a neutron monitor is discussed.

• Received 29 March 1956

DOI:https://doi.org/10.1103/PhysRev.103.328