The possibility of time focusing for very slow neutrons is considered. This
focusing may prove very useful in solving the problem of accumulating ultr
acold neutrons in a trap that are generated by a pulsed source. Diffraction
at a phase grating moving across a beam or resonance neutron-spin flip is
proposed to implement time-controlled changes in the neutron energy. (C) 20
00 MAIK "Nauka/Interperiodica".