Measurements are reported on the yield of neutrons from protons in the energy range from 7 to 17 MeV striking a stopping-length target of deuterium gas. This combination of beam and target is being investigated as an alternative to spallation for accelerator-driven transmutation technology with perhaps equivalent or lower energy cost per neutron. The concept includes neutrons produced from a cascade of reactions starting with the p + d reaction giving rise to subsequent fusion neutrons and neutrons from higher-order breakup reactions. In our application the incident proton energy is expected to be -100 MeV so that most of the neutrons produced in these reactions will be higher-energy neutrons that can undergo multiplication in surrounding beryllium or lead. The results reported here for lower proton energies indicate that the expected fusion and higher-order breakup reactions have been observed, and they provide the basis for a measurement at 100 MeV to confirm the larger proton-induced cascade benefits expected at higher proton energies.