Design of the neutron slit package for Femi chopper prototype of CSNS

BackgroundFermi chopper is the key equipment for monochromating the neutron beam in an inelastic neutron scattering spectrometer, and its performance will affect the resolution and counting rate of the spectrometer. The core component of Fermi chopper is neutron slit package, which is composed of neutron absorbing material and transparent material, and selects multiple single wavelength pulsed neutrons by high-speed rotation.PurposeThe study aims to design suitable slit packages for Fermi chopper prototype of China spallation neutron source (CSNS).MethodsAccording to the common experimental conditions of inelastic scattering, the development target of the Fermi chopper prototype was determined, then three typical slit packages were designed, and the feasibility of the design was verified by MCStas software simulation.ResultsThe simulation results show that: (1) the three kinds of slits can achieve a resolution of 2%~10% in the wavelength range of 0.02~0.50 nm, and the neutron decay rate and the slit packet tr