Ultra Cold Neutron sources are based on solid deuterium (sD2) at temperatures around 5 K. Under pulsed neutron production, an appreciable decrease in neutron intensities has observed, which affects their efficiency for fundamental interaction physics experiments. Two of the leading UCN sources at PSI and LANL joined forces with the NC State University nuclear physics group to understand this UCN intensity decrease. The study shows that the decrease can be completely explained by the build-up of frost on the sD2 surface during operation. Pulsed proton beams hitting the spallation targets generate heat pulses causing cycles of D2 sublimation and subsequent resublimation on the sD2 surface. Even very small frost flakes can act as total reflectors for UCN and cause an intensity decrease.
This paper was selected as a European Physics Journal Highlight! The press release can be found here.
Read the whole paper here!
The Fundamental Neutron Physics Summer School that we hosted at NC State from July 16-20 was a resounding success! We had around 70 combined participants plus speakers, with ~11 visiting us from Europe, ~6 from Canada and 1 from Japan. The lecture program covered essential topics from top researchers on nuclear, particle, and astrophysics with low energy neutrons. There were tours to the PULSTAR nuclear reactor on NCSU’s campus, and the 10 Mega-Volt Tandem accelerator and the Free-electron laser based High Intensity Gamma Ray source at TUNL. There was even a fun excursion to a local baseball game!
Our paper exploring the current experimental information on the 39K(p,γ)40Ca reaction cross section was just accepted in Physical Review C! This reaction is critical for explaining the peculiar elemental abundance patterns in the Globular Cluster NGC 2419, which can help us understand how the galaxy evolved. We found that inconsistencies in cross section measurements make the uncertainty in this rate larger than previously assumed, thus further experimental efforts should be aimed at investigating the 39K(p,γ)40Ca cross section.
Graduate student Caleb Marshall’s paper describing the design, construction, and testing of the FENRIS group’s focal plane detector was accepted into IEEE Transactions on Instrumentation and Measurement! This paper is the culmination of many years of hard work by Caleb and his co-authors.
The Ultra Cold Neutron source project has just submitted a new publication (https://arxiv.org/abs/1804.08616) related to our 2016 study of solid deuterium growth. This result is part of Graham Medlin’s PhD thesis.