Ultra-Cold Neutrons (UCN) have energies ~ 10^-7 eV. Their characteristics are described in another paper at this conference. Here, we explain the principle of a super-thermal out of pile UCN source and describe some recent development work and the design of such a source, which can produce higher UCN densities than other types of sources. This new source, using down scattering of 10 A neutrons in pure 4He has advantages for all experiments involving the storage of UCN (the search for a neutron electric dipole moment and neutron lifetime).