One of the instruments being considered for the ESS is a thermal chopper spectrometer, intended for the study of lattice vibrations and magnetic excitations. However, as the ESS will be a long pulsed source, we propose a very long instrument (180–300 m). We here present a guide system that can achieve a flux of 3.47 ×108 n/(s·cm2) and a resolution of dE/E = 5.3% for 1 Å neutrons on the sample with a transport efficiency of 80%. Furthermore, we demonstrate the efficiency of the instrument using a virtual experiment measuring an elastic line width