Study of neutron-induced ionization in helium and argon chamber gases

We present studies of helium- and argon-filled ionization chambers exposed to intense neutron fluxes from PuBe neutron sources (En=1–10 MeV). The sources emit about 108 neutrons per second. The number of ion pairs in the chamber gas volume per incident neutron is derived. While limited in precision because of a large gamma ray background from the PuBe sources, our results are consistent with the expectation that the neutrons interact purely elastically in the chamber gas.