(a) The correlation chopper on CORELLI, made of carbon fibre and consisting of N = 255 open/closed elements, arranged in a pseudorandom sequence. (b) The modulated incident neutron spectrum, characterized by the beam monitor immediately behind the correlation chopper running at 240 Hz that is in synchronization with the master pulse of the accelerator at constant phase offset t0. The grey areas indicate the TOF windows where the chopper is in the open position, and the blue curve is the measured neutron counts. (c) Schematic time–distance diagram, illustrating how neutrons with different incident energies pass through the correlation chopper, are scattered at the sample position with different energy transfers and arrive at the same time at the detector. t1 specifies the time of flight that incident neutrons travel from the source to the correlation chopper, t is the total time of flight that neutrons travel from the source to the detector, and t0 denotes the phase offset between the first element of the sequence and the start of the neutron pulse at the source. The black line represents the elastic scattering process, whereas the other lines show scattering events that involve energy transfer and therefore a change in the neutron velocity. (d) The self-correlation of the actual correlation chopper is approximately a δ function.