Speaker
Description
VESUVIO is a spectrometer at the ISIS Neutron and Muon Source, Rutherford Appleton Laboratory (United Kingdom) that allows the measurement of the total cross-section of a sample material by the transmission and time of flight techniques, over a range of five decades in energy (10$^{-3}$ to 10$^{2}$ eV). At the same time, it allows a precise determination of the effective temperature of each element present in the sample by using 198 detectors that are spatially distributed around the sample.
A neutron experiment was performed at VESUVIO on a solid ethane (C$_2$H$_6$) sample at 80 K. This material is an organic compound with a high protonic density and a low rotational energy band in its frequency spectrum, which makes it a good candidate to be used as a cryogenic moderator material. In a previous work (ND2016) we have presented experimental and calculated results for liquid Ethane at 100 K and 175 K, emphasizing its capacity to act as a “cool” moderator over an extended temperature range.
The phonon density of states of solid Ethane was evaluated using density functional theory techniques (DFT), and used as input for the NJOY Nuclear Data Processing system. The total cross section thus generated shows a very good agreement with the measured points, which represents a preliminary validation of the scattering kernel construction and the cross section library generated in ENDF and ACE formats.
Effective temperatures of hydrogen and carbon in the ethane molecule were obtained by modeling the deep inelastic scattered neutrons in the time of flight spectrum measured at each detector. The effective temperatures of hydrogen and carbon in the ethane molecule were determined by analyzing the time-of-flight spectra of the scattered neutrons measured at each detector. The agreement between these results and the effective temperature estimate obtained by means of a DFT of the simulated vibrational spectrum is also discussed.