PF2 - Ultracold neutron facility

Ultracold neutrons (UCN) with wavelengths around 1000 Å have several unique features: one of them is that they are totally reflected from the surface of most materials under any angle of incidence. This offers the possibility of storing neutrons in so called neutron bottles (or traps) for the observation of several fundamental characteristics of the neutron itself.

The facility PF2 operates a steady-state high-flux ultracold and very cold neutron source, which is unique in the world. In contrast to many instruments at the ILL, scientific users bring their whole experimental apparatus to PF2 to connect it to one of our beam ports.

Our source can serve four experiments with UCN (PF2/MAM, PF2/UCN, PF2/EDM, PF2/TEST), and one experiment using VCN (PF2/VCN) simultaneously.


  • the search for a neutron electric dipole moment;
  • neutron beta decay studies in a magnetic traps as well as in liquid and solid wall traps;
  • gravitationally bound quantum states;
  • ultracold neutrons (UCN) spectroscopy and diffractometry and optics;
  • very cold neutrons (VCN) interferometry;
  • UCN quasielastic heating studies;
  • the development of a neutron microscope and UCN monochromators, etc;
  • investigation of materials suited in UCN experiments