We report on the fabrication and use of deuterated polyethylene as a coating material for ultra-cold neutron (UCN) storage and transport. The Fermi potential has been determined to be 214 neV, and the wall loss coefficient η is 1.3 × 104 per wall collision. The coating technique allows for a wide range of applications in this field of physics. In particular, flexible and quasi-massless UCN guides with slit-less shutters and seamless UCN storage volumes become possible. These properties enable the use in next-generation measurements of the electric dipole moment of the neutron.

A first experimental demonstration of a new type of magnetic trap for ultra-cold neutrons is presented. High-field seeking spin-states are trapped in a potential formed by the magnetic field of a straight wire and a repulsive coating on the wire surface. Life-times of the trapped neutrons of 60 s could be observed. This configuration can in principle be used to form bound states of the wave function on the surface of the wire to probe new forces at short distances. Further applications include the use as a guide and selector for perfectly polarized neutrons.

We have developed a very cold neutron spin interferometer (VCNSI) for investigations in neutron optics and spectroscopy. As a first step towards such a powerful spin interferometer, a polarized neutron beam line with a mean wavelength of 5.8nm has been installed at the PF2/VCN beam position at the ILL. We obtained spin interference with high visibility of about 0.79. We made first tests of its feasibility for neutron spin echo spectrometry.

We report experiments testing the question whether or not ultra-cold neutrons (UCN) stored in traps with total-reflecting walls are temporarily adsorbed to the walls. A hypothetical process of sticking to the walls is theoretically intriguing but it can apparently make plausible the puzzling observations made in UCN storage experiments over the years.

In unconventional storage experiments we filled ultracold neutrons (UCN) into a Fomblin-grease coated trap and then immediately removed the UCN from the storage volume by an absorber, until their residual density in the trap was measured to be negligible. When subsequently the absorber was withdrawn a significant number of UCN of higher energies emerged from the trap. Their appearance cannot be attributed to heating or cooling of residual UCN. Further experiments were performed to investigate the origin of these UCN which we call `late UCN'. We noticed that application of a magnetic field gradient at the trap wall as well as a replacement of Fomblin grease on the surface by Fomblin oil gave rise to small but measurable alterations of storage behavior. These phenomena are consistent with the hypothesis of temporary adhesion of a few UCN to a rough wall.

The first experiment to seek corrections to standard plane-wave quantum mechanics was performed. Extra transmission of cold neutrons at the total reflection angle was observed at the level 10−4, and the results give information about the packet-spectrum tail according to the hypothesis of the de Broglie wave-packet nature of the neutron.