A comparison of time-of-flight and Larmor modulation neutron powder diffraction at a continuous reactor source

A neutron powder diffraction instrument for application at a continuous rea ctor source based on time-of-flight (TOF) is compared with an instrument ba sed on Larmor modulation (LM). For instruments with a similar wave-vector r esolution (delta q/q = 4 x 10(-3)) it is found that the signal-to-noise rat ios in a TOF experiment are generally better when using a wide wavelength n eutron spectrum. This is caused by the fact that the noise in a LM experime nt comes from the integrated neutron flux scattered in the detector, while in TOF the noise stems only from the intensity scattered into individual ti me channels. (C) 1999 Elsevier Science B.V. All rights reserved.