Focus: Project of a space and time focussing time-of-flight spectrometer for cold neutrons at the spallation source SINQ of the paul scherrer institute

Abstract

Abstract The physical design of FOCUS, a new time-of-flight (TOF) spectrometer for cold neutrons located at the continuous spallation source SINQ at the Paul Scherrer Institute/CH is presented. The main purpose of the instrument is to provide a versatile TOF machine being suited for a large variety of applications. The concept of the instrument consists in the combination of a doubly focussing monochromator with a Fermi-chopper. The monochromator will be provided with variable curvatures in both horizontal and vertical direction. By variable distances between the main spectrometer components FOCUS will have the option to be operated either in time focussing or monochromatic focussing mode for quasielastic and inelastic scattering applications, respectively. By means of two interchangeable monochromators a continuous wavelength band ranging from 2A up to 18A will be accessible. Monte Carlo simulations for an ideal Pb-target at SINQ show that for 4A and 6A and in its time focussing mode FOCUS will yield com...