| At the Quasielastic Neutron Spectrometer (QENS) instrument at the Intense Pulsed Neutron Source (IPNS) of Argonne National Laboratory neutrons are scattered from a sample and energy analyzed by Bragg diffraction. To filter out the higher order diffraction patterns, beryllium is placed before the detector bank. Beryllium has a energy cutoff at 3.96 Å, preventing the higher order reflections from being detected. Multiple scattering within the beryllium allows some of these higher order neutrons through the filter, which are a source of noise.; The purpose of this project was to develop methods for limiting this leakage. A Monte Carlo simulation of the QENS analyzer arms was developed to meet this goal. Through careful analysis of the simulations and construction of the filters according to the results, this goal was reached. A significant fraction of the leakage was eliminated with a minimum of loss in the desired neutrons. |
