Ion chambers used to monitor the secondary hadron and tertiary muon beam in the NuMI neutrino beamline will be exposed to background particles, including low energy neutrons produced in the beam dump. To understand these backgrounds, we have studied 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.
@article{arxiv.physics/0405016,
title = {Study of Neutron-Induced Ionization in Helium and Argon Chamber Gases},
author = {D. Indurthy and A. R. Erwin and D. Harris and S. Kopp and M. Proga and R. M. Zwaska},
journal= {arXiv preprint arXiv:physics/0405016},
year = {2009}
}