Towards a high-resolution TOF-MIEZE spectrometer with very cold neutrons

We report the first experimental test of TOF-MIEZE technique using very cold neutrons (VCNs) towards high-resolution quasi-elastic neutron scattering spectroscopy. TOF-MIEZE is a type of neutron resonance spin echo spectroscopy with a combination of the time-of-flight (TOF) method and modulation of intensity by zero effort (MIEZE). A compact MIEZE instrument was constructed at the VCN beam port at the High Flux Reactor at the Institut Laue Langevin. By accumulating individual oscillations of raw data, we observed a TOF-MIEZE signal with an effective frequency of 50 kHz in a wavelength band of 4-6 nm. The signal contrasts were 0.59±0.04 and 0.29±0.03 for wavelengths of 4 nm and 6 nm, respectively. The Fourier time was estimated to be 70 ns with 6 nm VCNs in the experimental set-up.