Inelastic neutron scattering (INS) is a widely used technique for studying condensed matter that allows to obtain detailed data on magnetic and atomic dynamics in a large volume of momentum and energy transfer space. At the beginning of this century, breakthrough developments were carried out in the technology of measurement of inelastic neutron scattering resulting in a radical increase in the quality and quantity of the data obtained by measuring the four-dimensional scattering law function S(Q, ω). Four possible options for the development of general-purpose INS spectrometers for the source “NEPTUN” are considered in the report:

1. Thermal neutron direct geometry spectrometer, with a wide Q - ω range and moderate resolution.
2. High resolution direct geometry spectrometer at a cold neutron source.
3. Thermal neutron inverse geometry spectrometer with a wide range (up to 300 meV) of energy transfers and with a large solid angle of ~6 steradians.
4. High resolution inverse geometry spectrometer at a cold neutron source.