  The use of argon as a detection and shielding medium for neutrino and dark
matter experiments has made the precise knowledge of the cross section for
neutron capture on argon an important design and operational parameter. Since
previous measurements were averaged over thermal spectra and have significant
disagreements, a differential measurement has been performed using a
Time-Of-Flight neutron beam and a $\sim$4$\pi$ gamma spectrometer. A fit to the
differential cross section from $0.015-0.15$\,eV, assuming a $1/v$ energy
dependence, yields $\sigma^{2200} = 673 \pm 26 \text{ (stat.)} \pm 59 \text{
(sys.)}$\,mb.
