Thermal neutron three-axis spectrometer with polarization analysis

IN20 and the TASSE spectrometry

The movie shows the very first steps of an experiment performed on IN20 in 2008 on parahydrogen. The instrument was operated in the TASSE mode combing both neutron triple axis spectrometry (TAS), which provides the energy analysis, and neutron spin echo (SE), which provides the high energy resolution.

Hydrogen is thought to be the fuel of the future since it is abundant and non-polluting. One promising material for the storage of hydrogen is nanoscrolls (a special form of carbon nanotubes). However we still have to dominate the storage/release process and thus we must understand better how hydrogen molecules or atoms bind to carbon atoms.

Such a study is very difficult for four main reasons:

  1. the binding energies are extremely weak (μeV) i.e. the picosecond time scale. Only IN20-TASSE offers a good enough energy resolution.
  2. normal hydrogen (orthohydrogen), a strong incoherent neutron scatterer, must be replaced by parahydrogen much more difficult to obtain.
  3. the mount of adsorbed hydrogen in the sample is small compared to the amount of carbon.

The experiment was very successful and one of the results is that, below 10K, the parahydrogen line halfwidth remains roughly constant at 3 mev and the energy of this line is also constant