**4. Summary**

A mixed beam of atomic and molecular deuterons and protons, accelerated to 5 MeV, impinges on a thick beryllium target, and the resultant neutron spectrum is the sum of the spectra from the 9Be(d,n)10B reaction (higher-energy neutrons) and the 9Be(p,n)9B reaction (lower-energy neutrons). The neutron energy spectrum is manipulated by adjusting the ratio of protons and deuterons to mimic the neutron spectra from an IND exposure for medical triage and bio‐ dosimetry studies. Specifically, it mimics the Hiroshima gun-type bomb spectrum at a relevant distance from the epicenter (1–1.5 km) and is significantly different from a standard reactor fission spectrum because the bomb spectrum changes as the neutrons are transported through air. The neutron spectrum of this irradiator was measured and is verified comparable with the Hiroshima bomb spectrum at 1.5 km. About 79% of the radiation dose is delivered by neutrons and He rest by γ-rays. A comparison of the biological effect of neutron and X-ray exposure on micronuclei yields in peripheral lymphocytes demonstrated that the IND-spectrum irradiator described above gives RBE values within the expected range.
