Electron-volt spectroscopy at a pulsed neutron source using a resonance detector technique

We present measurements on the energy resolution of a
neutron Resonance Detector Spectrometer (RDS) using
Pb and 4He/H2 mixture scattering samples.
The final neutron energy is selectively measured by
means of an absorbing 238U foil which emits a prompt
gamma ray cascade generated by (n,?) reactions,
revealed employing a conventional NaI(Tl) scintillator,
properly shielded.
Despite a low signal to background ratio, it is possible to
identify four recoil peaks corresponding, in energy, to the
four resonances of the 238U in the epithermal region and
compare their position with the prediction. Moreover, the
double difference technique, which imply the use of two
foils of different thickness, shows to enhance the energy
resolution, as indicated by the reduction of the intrinsic
width of the recoil peak at 6.6 eV.