The resonant detector and its application to epithermal neutron spectroscopy

New perspectives for epithermal neutron spectroscopy are being opened by the development of the resonant detector (RD) and its use on inverse geometry time of flight spectrometers at spallation sources. The RD was first proposed in the 1980s and was recently brought to a performance level exceeding conventional neutron-sensitive Li-glass scintillator detectors. It features a photon counter coupled to a neutron analyzer foil. Resonant neutron adsorption in the foil results in the emission of prompt gamma rays that are detected in the photon counter. The dimensions of the RD set the construction of detector arrays geometry. The main results of the research on this kind of detector are reported leading to the present optimized RD design based on a combination of YAP scintillation photon counter and uranium or gold analyzer foils. This detector has already been selected for application in the upgrade of the VESUVIO spectrometer on ISIS. A special application is the Very Low Angle Detector (VLAD) bank, which will extend the kinematical region for neuron scattering to low momentum transfer (<10 Angstrom(-1)) whilst still keeping energy transfer > 1 eV, thus allowing new experimental studies in condensed matter systems. The first results of the tests made with prototype VLAD detectors are presented, confirming the usefulness of the RD for measurements at the scattering angles as low as 2-5degrees.