Thick Target Fast Neutron Yield from 15-Mev Deuteron and 30-Mev Alpha-Bombardment

The total yield and angular distribution of fast neutrons from bombardment of thick targets of pure Be, Al, Ti, Cr, Mn, Co, Cb, Mo, Ag, Cd, Ta, Au, Pb, and Bi by 15-Mev deuterons and 30-Mev alpha-particles was measured. These studies were made using the reaction ${\mathrm{S}}^{32}\mathrm{}(n,p)\mathrm{}{\mathrm{P}}^{32}$ as a threshold detector and also with fission ionization chambers. The total neutron yield per second per μamp of the cyclotron beam, $N$, was observed to decrease with increase in nuclear charge, $Z$, of the target according to the approximate empirical equations, $logN=10.18-0.0234Z$ for deuteron bombardment and $logN=9.68-0.0234Z$ for alpha. In all cases studied, the angular distribution of fast neutrons from target bombarded by deuterons showed a pronounced peak in the yield in the forward direction.