According to layout of a triple-axis spectrometer (TAS)

neutron beam parameters at the sample position

such as the homogeneity

divergence and flux

were calculated by Monte-Carlo simulation. The results show that using a double-focusing monochromator

the beam flux is 1.54 times larger

but the neutron distribution is worse

than using a flat monochromator

while the vertical maximum divergence increases to 4°. Vertical divergence of the neutrons decreases with increasing focusing lengths

while the beam homogeneity does not change obviously. A pyrolytic graphite (PG) filter is suitable for neutrons in wavelengths of less than 0.4 nm

while a Be filter is better than PG filter for neutrons in wavelengths of longer than 0.4 nm.