Ultracold neutrons

Cross Section for “Ultracold” Neutrons

Very cold neutrons (typical wavelengths are about 102 Ä) are available by recently developed techniques 2. The features of the scattering of these “ultracold” neutrons are investigated in the present paper discussing a few examples of magnetic scattering. The diffraction of neutrons by the vortex lattice in superconductors is treated as an example of elastic scattering, while in most other case...

Neutron lifetime measured with stored ultracold neutrons.

Measuring Neutron Beta Decay “A” Parameter Using Ultracold Neutrons

The UCNA experiment is designed to measure the neutron decay beta asymmetry (the "A" parameter) to very high precision (<0.5%), using the ultracold neutron (UCN) source at the Los Alamos National Lab. After a successful commissioning run in 2007, data were taken in 2008 which will lead to a 1% measurement of A. In this talk, I will discuss major improvements we made in 2008, and report the stat...

Bulk effects in the coherent inelastic scattering of ultracold neutrons

With the use of theory developed earlier, bulk effects in ultracold neutron coherent inelastic scattering are considered both for solid and liquid target samples related to energy and momentum exchange with phonon and diffusion-like modes. For the neutron in a material trap, differential and integral probabilities for the energy transfer per bounce are presented in a simple analytic form which ...

Neutron lifetime measurements using gravitationally trapped ultracold neutrons

Experiment using gravitationally trapped ultracold neutrons (UCNs) to measure the neutron lifetime is reviewed. The precise value of the neutron lifetime is of fundamental importance to particle physics and cosmology. In our experiment, the UCN storage time is brought closest ever to the neutron lifetime: the probability of the UCN loss from the trap was only 1% of that for neutron β-decay. The...