Demonstration with very-cold neutrons of developments in Fourier time-of-flight

We demonstrate recent developments in neutron Fourier time-of-flight in an experiment using very-cold neutrons. The implementation of a novel sinusoidal stator design eliminates a systematic effect associated with triangular modulation in existing Fourier choppers. Although transmission is inherently higher for triangular modulation, it is demonstrated that only about 3 % additional measurement time is needed with sinusoidal modulation to achieve the same statistical uncertainty. In addition, a new neutron-based technique that does not require additional instrumentation is employed to determine the chopper phase offset.