@article{phan_wei_beaumont_bouman_clayton_currie_ito_ramsey_seidel_2021, title={A study of DC electrical breakdown in liquid helium through analysis of the empirical breakdown field distributions}, volume={129}, ISSN={["1089-7550"]}, DOI={10.1063/5.0037888}, abstractNote={We report results from a study on electrical breakdown in liquid helium using near-uniform-field stainless steel electrodes with a stressed area of ∼0.7cm2. The distribution of the breakdown field is obtained for temperatures between 1.7 K and 4.0 K, pressures between the saturated vapor pressure and 626 Torr, and with electrodes of different surface polishes. A data-based approach for determining the electrode-surface-area scaling of the breakdown field is presented. The dependence of the breakdown probability on the field strength as extracted from the breakdown field distribution data is used to show that breakdown is a surface phenomenon closely correlated with Fowler–Nordheim field emission from asperities on the cathode. We show that the results from this analysis provide an explanation for the supposed electrode gap-size effect and also allow for a determination of the breakdown-field distribution for arbitrary shaped electrodes. Most importantly, the analysis method presented in this work can be extended to other noble liquids to explore the dependencies for electrical breakdown in those media.}, number={8}, journal={JOURNAL OF APPLIED PHYSICS}, author={Phan, N. S. and Wei, W. and Beaumont, B. and Bouman, N. and Clayton, S. M. and Currie, S. A. and Ito, T. M. and Ramsey, J. C. and Seidel, G. M.}, year={2021}, month={Feb} }
 @article{korobkina_medlin_wehring_hawari_huffman_young_beaumont_palmquist_2014, title={Ultracold neutron source at the PULSTAR reactor: Engineering design and cryogenic testing}, volume={767}, ISSN={1872-9576}, DOI={10.1016/j.nima.2014.08.016}, abstractNote={Construction is completed and commissioning is in progress for an ultracold neutron (UCN) source at the PULSTAR reactor on the campus of North Carolina State University. The source utilizes two stages of neutron moderation, one in heavy water at room temperature and the other in solid methane at ~40K, followed by a converter stage, solid deuterium at 5 K, that allows a single down scattering of cold neutrons to provide UCN. The UCN source rolls into the thermal column enclosure of the PULSTAR reactor, where neutrons will be delivered from a bare face of the reactor core by streaming through a graphite-lined assembly. The source infrastructure, i.e., graphite-lined assembly, heavy-water system, gas handling system, and helium liquefier cooling system, has been tested and all systems operate as predicted. The research program being considered for the PULSTAR UCN source includes the physics of UCN production, fundamental particle physics, and material surface studies of nanolayers containing hydrogen. In the present paper we report details of the engineering and cryogenic design of the facility as well as results of critical commissioning tests without neutrons.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, author={Korobkina, E. and Medlin, G. and Wehring, B. and Hawari, A. I. and Huffman, P. R. and Young, A. R. and Beaumont, B. and Palmquist, G.}, year={2014}, month={Dec}, pages={169–175} }