We describe an experimental installation for a new test of the weak
equivalence principle for neutron. The device is a sensitive gravitational
spectrometer for ultra-cold neutrons allowing to precisely compare the gain in
kinetic energy of free falling neutrons to quanta of energy ${\hbar}{\Omega}$
transferred to the neutron via a non stationary device, i.e. a quantum
modulator. The results of first test experiments indicate a collection rate
allowing measurements of the factor of equivalence $ { \gamma}$ with a
statistical uncertainty in the order of $5{\times}10^{-3}$ per day. A number of
systematic effects were found, which partially can be easily corrected. For the
elimination of others more detailed investigations and analysis are needed.
Some possibilities to improve the device are also discussed.Comment: Submitted to NIM