Oak Ridge National Laboratory

Physics Division

Physics Division Seminars

Physics Division Seminars bring us speakers on a variety of physics related subjects. Usually these are held in the Building 6008 large Conference Room, at 3:00 pm on the chosen day, but times and locations may vary. For more information, contact our seminar chairman,

Alfredo Galindo-Uribarri
Tel (Office): (865) 574-6124  (FAX): (865) 574-1268


Thu., March 10, 2011, at 3:00 p.m. (refreshments at 2:40 p.m.)

Ultracold Neutrons: a laboratory for low-energy particle physics

Chen-Yu Liu, Indiana University, Bloomington, IN
Building 6008 Conference Room

Ultracold neutrons (UCN) are free neutrons with maximum energy of 300 neV, equivalent to ~1 mK. Their kinetic energy is so low that they may be contained and accumulated in material bottles, magnetic traps, and the Earth's gravitational field, for durations up to hundreds of seconds. The kinetic energy is comparable to the Zeeman splitting in a magnetic field of a few Tesla, and neutron state with 100% spin polarization can be prepared through simple field filtering. Storability and easy polarization of UCN make them the tool of choice in many experiments to measure fundamental properties of the neutron to unprecedented precision. Polarized UCN is well-suited for experiments to measure parity violation and search for exotic process that breaks time reversal symmetry. The most precise measurements of the neutron electric dipole moment and the neutron beta-decay lifetime all employ UCN in a trap. Any innovation that increases the storable UCN density and the deliverable UCN flux will simplify many technical difficulties in these challenging experiments. For example, a larger UCN density would reduce the size of most EDM experiments making the implementation of stringent magnetic field uniformity and large electric field a less daunting task. In this talk, Dr. Liu will give a brief overview of the fundamental physics research using UCN and present recent results in UCN source development.