Beam homogeneity

collimation and flux at the exit (C3) of a cold neutron guide(NG) were simulated by MCSTAS1.9 based on the layout of a cold neutron source (CNS) and NG.. The optimization shows that a) the distance (LS-NG) between CNS and the NG entrance should be as short as possible; b) the flux and Y divergence increased by 24% and 61%

respectively

while the supermirror factor m increased from 1.5 to 3.0; c) divergence in the normal direction of NG curved pane (Y) can be described with a Gaussian function

but divergence in the direction of curved plane (X) was in strips; and d) when m=1.5 and LS-NG=2.29 m

the Y-divergence was 0.86° and the flux was 2.44×107 cm–2·s–1.