Figure 4.4.1.2 

Schematic diagram for performing diffraction experiments at steady-state and pulsed neutron sources. On the left we see the familiar monochromator crystal allowing a constant (in time) beam to fall on the sample (centre left), which then diffracts the beam through an angle 2θ_s into the detector. The signal in the latter is also constant in time (lower left). On the right, the pulsed source allows a wide spectrum of neutrons to fall on the sample in sharp pulses separated by Δt (centre right). The neutrons are then diffracted by the sample through 2θ_s and their time of arrival in the detector is analysed (lower right). The centre figure shows the time-averaged flux at the source. At a reactor, we make use of a narrow band of neutrons (heavy shading), here chosen with λ = 1.5 Å. At a pulsed source, we use a wide spectral band, here chosen from 0.4 to 3 Å and each one is identified by its time-of-flight. For the experimentalist, an important parameter is the integrated area of the two-shaded areas. Here they have been made identical.