UCN, the ultracold neutron source -- neutrons for particle physics

Neutron lifetime measured with stored ultracold neutrons.

The Spallation Target for the Ultra Cold Neutron Source Ucn

A source of ultra cold neutrons, based on the spallation process is under construction at PSI. With the help of a fast kicker the whole ~1 MW proton beam (590 MeV, 2 mA) from the accelerator will be switched onto the UCN spallation target for approximately 8 seconds every 15 minutes. The spallation neutrons are thermalized in a large heavywater moderator at room temperature and further cooled i...

First Measurement of the Neutron β-Asymmetry with Ultracold Neutrons

R. W. Pattie Jr., 2 J. Anaya, H. O. Back, 2 J. G. Boissevain, T. J. Bowles, L. J. Broussard, R. Carr, D. J. Clark, S. Currie, S. Du, B. W. Filippone, P. Geltenbort, A. Garćıa, A. Hawari, K. P. Hickerson, R. Hill, M. Hino, S. A. Hoedl, 9 G. E. Hogan, A. T. Holley, T. M. Ito, 5 T. Kawai, K. Kirch, S. Kitagaki, S. K. Lamoreaux, C.-Y. Liu, J. Liu, M. Makela, 11 R. R. Mammei, J. W. Martin, 12 D. Mel...

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...

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...