UCN gravity spectrometry using neutron interference filters for fundamental investigations in neutron optics

Time-of-flight Fourier UCN spectrometer

“…Such spectrum has never been measured by the classical TOF method, but we had the results of the measurement of the convolution of the filter transmission function with the transmission function of another filter-analyzer (so-called scanning curve). The measurement was made in 2000 using the Gravity UCN spectrometer [12,13,44]. Knowing the convolution of two transmission functions it is possible to determine the difference between the energies of two lines with a high precision, but not their absolute values.…”

“…It is shown in Figure1. Ultracold neutrons are fed to the entrance chamber through the UCN neutron guide and, after a number of reflections, fall down the annular channel with the lower section closed by a monochromator, which is a five-layer Ni-Ti interference filter [12,13,43]. To suppress the background of neutrons with energies higher than the effective potential of nickel, the filter-monochromator is combined with a multilayer "superwindow filter [12].…”

“…To test the spectrometer, four objects were chosen: three interference filters [12,13,43] (hereinafter referred to as filter 1,2,3) and diffraction grating. Their short descriptions are given below.…”

“…Filter 3 was characterized by the splitting of the transmission line (see details in [12,13,44]). In the regime of Fourier spectrometry filters 1-3 together with the filter-superwindow served as a monochromator.…”

“…Specifically, the gravity UCN spectrometry [7][8][9][10][11][12][13][14] and the spectrometry based on the use of quantum spectrometric devices (various interference filters) [11,12,[15][16][17] have received widespread use.…”