Ultracold Neutron

My research interest in UCN source development grew out of my dissertation research, in which I helped to develop the working prototype for this intense superthermal ultracold neutron source at Los Alamos. My main contribution to this effort was to solve the short UCN lifetime problem, which inhibited the predicted large UCN output. In fact, this problem had been preventing the practical success of several groups in America and Europe that had been attempting to construct solid deuterium superthermal sources for several decades. Our group investigated a possible UCN loss mechanism mediated by a particular molecular state of deuterium. In solid deuterium sources, the finite concentration of para-deuterium (spin 1) can retain unquenched rotational energy even at low temperatures. Together with Prof. Young and Dr. Lamoreaux, we completed a series of theoretical calculations which showed that this effect results in excessive upscattering of neutrons out of the ultracold state.

To mitigate this serious source of loss, we built an ortho/para-deuterium converter, and a molecular Raman spectroscope optimized to monitor the ortho/para ratio of the converted gas. In the spring of 2000, the UCN experiment overcame the short-lifetime problem using these instruments. The greatly enhanced UCN flux enabled the collaboration to conduct a comprehensive set of studies on UCN production physics in solid deuterium. In the summer of the same year, the experiment at LANL stored the highest density of UCN ever achieved.

The success of this research encouraged the UCN field worldwide. It has helped to push forward several million-dollar proposals to build solid deuterium UCN facilities at, for example, the Paul Scherrer Institute in Switzerland and North Carolina State University. Moreover, the breakthroughs in source intensity are expected to enhance the performance of fundamental physics experiments with UCN, which would otherwise be statistically limited. These experiments provide sensitive tests of the Standard Model of Particle Physics and its extensions, and include neutron lifetime and decay-product correlation measurements, searches for the neutron EDM, and searches for neutron-antineutron oscillations.

 

Calculations

 

AFP Spin Flipper

 

UCN Source

Solid Oxygen Crystal Growth Study

 

Geant4 UCN Simulations

 

 

 

UCN

eEDM

nEDM