@article{bosak_dubois_korobkina_lychagin_muzychka_nekhaev_nesvizhevsky_nezvanov_saerbeck_schweins_et al._2023, title={Effect of Nanodiamond Sizes on the Efficiency of the Quasi-Specular Reflection of Cold Neutrons}, volume={16}, ISSN={["1996-1944"]}, DOI={10.3390/ma16020703}, abstractNote={Nanomaterials can intensively scatter and/or reflect radiation. Such processes and materials are of theoretical and practical interest. Here, we study the quasi-specular reflections (QSRs) of cold neutrons (CNs) and the reflections of very cold neutrons (VCNs) from nanodiamond (ND) powders. The fluorination of ND increased its efficiency by removing/replacing hydrogen, which is otherwise the dominant cause of neutron loss due to incoherent scattering. The probability of the diffuse reflection of VCNs increased for certain neutron wavelengths by using appropriate ND sizes. Based on model concepts of the interaction of CNs with ND, and in reference to our previous work, we assume that the angular distribution of quasi-specularly reflected CNs is narrower, and that the probability of QSRs of longer wavelength neutrons increases if we increase the characteristic sizes of NDs compared to standard detonation nanodiamonds (DNDs). However, the probability of QSRs of CNs with wavelengths below the cutoff of ~4.12 Å decreases due to diffraction scattering on the ND crystal lattice. We experimentally compared the QSRs of CNs from ~4.3 nm and ~15.0 nm ND. Our qualitative conclusions and numerical estimates can help optimize the parameters of ND for specific practical applications based on the QSRs of CNs.}, number={2}, journal={MATERIALS}, author={Bosak, Alexei and Dubois, Marc and Korobkina, Ekaterina and Lychagin, Egor and Muzychka, Alexei and Nekhaev, Grigory and Nesvizhevsky, Valery and Nezvanov, Alexander and Saerbeck, Thomas and Schweins, Ralf and et al.}, year={2023}, month={Jan} }
 @article{chernyavsky_dubois_korobkina_lychagin_muzychka_nekhaev_nesvizhevsky_nezvanov_strelkov_zhernenkov_2022, title={Enhanced directional extraction of very cold neutrons using a diamond nanoparticle powder reflector}, volume={93}, ISSN={["1089-7623"]}, DOI={10.1063/5.0124833}, abstractNote={For more than a decade, detonation nanodiamond (DND) powders have been actively studied as a material for efficient reflectors of very cold neutrons (VCNs) and cold neutrons. In this work, we experimentally demonstrate, for the first time, the possibility of enhanced directional extraction of a VCN beam using a reflector made of fluorinated DND powder. With respect to the theoretical flux calculated from an isotropic source at the bottom of the reflector cavity, the gain in the VCN flux density along the beam axis is ∼10 for the neutron velocities of ∼57 and ∼75 m/s. The use of such reflectors for enhanced directional extraction of VCN from neutron sources will make it possible to noticeably increase the neutron fluxes delivered to experiments and expand the scope of VCN applications.}, number={12}, journal={REVIEW OF SCIENTIFIC INSTRUMENTS}, author={Chernyavsky, S. M. and Dubois, M. and Korobkina, E. and Lychagin, E. and Muzychka, A. Yu and Nekhaev, G. and Nesvizhevsky, V. V. and Nezvanov, A. Yu and Strelkov, A. and Zhernenkov, K. N.}, year={2022}, month={Dec} }
 @article{korobkina_berkutov_golub_huffman_hickman_leung_medlin_morano_rao_teander_et al._2022, title={Growing solid deuterium for UCN production}, volume={24}, ISSN={["1477-2655"]}, DOI={10.3233/JNR-220010}, abstractNote={We have experimentally studied growing a large (about 1 liter) ortho-deuterium crystal in a real UCN source cryostat and recorded the growing process optically using a camera. The best quality was observed when growing the crystal directly from a vapor phase. The crystal was grown at different mass flows of deuterium and annealed at different temperatures. Optimum conditions were found for both, obtaining an optically transparent crystal and cooling it down with minimal damage. We found that the quality, final shape and changes during annealing of the crystal are very much dependent on the temperature profile of the cryostat walls.}, number={2}, journal={JOURNAL OF NEUTRON RESEARCH}, author={Korobkina, Ekaterina and Berkutov, Igor and Golub, Robert and Huffman, Paul and Hickman, Clark and Leung, Kent and Medlin, Graham and Morano, Matthew J. and Rao, Thomas and Teander, Cole and et al.}, year={2022}, pages={179–191} }
 @article{aleksenskii_bleuel_bosak_chumakova_dideikin_dubois_korobkina_lychagin_muzychka_nekhaev_et al._2021, title={Clustering of Diamond Nanoparticles, Fluorination and Efficiency of Slow Neutron Reflectors}, volume={11}, ISSN={["2079-4991"]}, DOI={10.3390/nano11081945}, abstractNote={Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.}, number={8}, journal={NANOMATERIALS}, author={Aleksenskii, Aleksander and Bleuel, Markus and Bosak, Alexei and Chumakova, Alexandra and Dideikin, Artur and Dubois, Marc and Korobkina, Ekaterina and Lychagin, Egor and Muzychka, Alexei and Nekhaev, Grigory and et al.}, year={2021}, month={Aug} }
 @article{aleksenskii_bleuel_bosak_chumakova_dideikin_dubois_korobkina_lychagin_muzychka_nekhaev_et al._2021, title={Effect of Particle Sizes on the Efficiency of Fluorinated Nanodiamond Neutron Reflectors}, volume={11}, ISSN={["2079-4991"]}, DOI={10.3390/nano11113067}, abstractNote={Over a decade ago, it was confirmed that detonation nanodiamond (DND) powders reflect very cold neutrons (VCNs) diffusively at any incidence angle and that they reflect cold neutrons quasi-specularly at small incidence angles. In the present publication, we report the results of a study on the effect of particle sizes on the overall efficiency of neutron reflectors made of DNDs. To perform this study, we separated, by centrifugation, the fraction of finer DND nanoparticles (which are referred to as S-DNDs here) from a broad initial size distribution and experimentally and theoretically compared the performance of such a neutron reflector with that from deagglomerated fluorinated DNDs (DF-DNDs). Typical commercially available DNDs with the size of ~4.3 nm are close to the optimum for VCNs with a typical velocity of ~50 m/s, while smaller and larger DNDs are more efficient for faster and slower VCN velocities, respectively. Simulations show that, for a realistic reflector geometry, the replacement of DF-DNDs (a reflector with the best achieved performance) by S-DNDs (with smaller size DNDs) increases the neutron albedo in the velocity range above ~60 m/s. This increase in the albedo results in an increase in the density of faster VCNs in such a reflector cavity of up to ~25% as well as an increase in the upper boundary of the velocities of efficient VCN reflection.}, number={11}, journal={NANOMATERIALS}, author={Aleksenskii, Aleksander and Bleuel, Marcus and Bosak, Alexei and Chumakova, Alexandra and Dideikin, Artur and Dubois, Marc and Korobkina, Ekaterina and Lychagin, Egor and Muzychka, Alexei and Nekhaev, Grigory and et al.}, year={2021}, month={Nov} }
 @article{ahmed_alarcon_aleksandrova_baeßler_barron-palos_bartoszek_beck_behzadipour_berkutov_bessuille_et al._2019, title={A new cryogenic apparatus to search for the neutron electric dipole moment}, volume={14}, ISSN={1748-0221}, url={http://dx.doi.org/10.1088/1748-0221/14/11/P11017}, DOI={10.1088/1748-0221/14/11/P11017}, abstractNote={A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). This apparatus uses superfluid 4He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized 3He from an Atomic Beam Source injected into the superfluid 4He and transported to the measurement cells where it serves as a co-magnetometer. The superfluid 4He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of 2−3× 10−28 e-cm, with anticipated systematic uncertainties below this level.}, number={11}, journal={Journal of Instrumentation}, publisher={IOP Publishing}, author={Ahmed, M.W. and Alarcon, R. and Aleksandrova, A. and Baeßler, S. and Barron-Palos, L. and Bartoszek, L.M. and Beck, D.H. and Behzadipour, M. and Berkutov, I. and Bessuille, J. and et al.}, year={2019}, month={Nov}, pages={P11017–P11017} }
 @article{anghel_bailey_bison_blau_broussard_clayton_cude-woods_daum_hawari_hild_et al._2018, title={Solid deuterium surface degradation at ultracold neutron sources}, volume={54}, ISSN={1434-6001 1434-601X}, url={http://dx.doi.org/10.1140/epja/i2018-12594-2}, DOI={10.1140/epja/i2018-12594-2}, abstractNote={Solid deuterium (sD $ _2$ is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD $ _2$ must be sufficiently cold, of high purity and mostly in its ortho-state in order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD $ _2$ material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease of the UCN yield with time of operation after initial preparation or later treatment (“conditioning”) of the sD $ _2$ . We show that, in addition to the quality of the bulk sD $ _2$ , the quality of its surface is essential. Our observations and simulations support the view that the surface is deteriorating due to a build-up of D $ _2$ frost-layers under pulsed operation which leads to strong albedo reflections of UCN and subsequent loss. We report results of UCN yield measurements, temperature and pressure behavior of deuterium during source operation and conditioning, and UCN transport simulations. This, together with optical observations of sD $ _2$ frost formation on initially transparent sD $ _2$ in offline studies with pulsed heat input at the North Carolina State University UCN source, results in a consistent description of the UCN yield decrease.}, number={9}, journal={The European Physical Journal A}, publisher={Springer Nature}, author={Anghel, A. and Bailey, T. L. and Bison, G. and Blau, B. and Broussard, L. J. and Clayton, S. M. and Cude-Woods, C. and Daum, M. and Hawari, A. and Hild, N. and et al.}, year={2018}, month={Sep} }
 @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} }
 @article{yang_brome_butterworth_dzhosyuk_mattoni_mckinsey_michniak_doyle_golub_korobkina_et al._2008, title={Invited article: Development of high-field superconducting Ioffe magnetic traps}, volume={79}, number={3}, journal={Review of Scientific Instruments}, author={Yang, L. and Brome, C. R. and Butterworth, J. S. and Dzhosyuk, S. N. and Mattoni, C. E. H. and McKinsey, D. N. and Michniak, R. A. and Doyle, J. M. and Golub, R. and Korobkina, E. and et al.}, year={2008} }
 @article{ye_dutta_gao_kramer_qian_zong_hannelius_mckeown_heyburn_singer_et al._2008, title={Relaxation of spin polarized He-3 in mixtures of He-3 and He-4 below the He-4 lambda point}, volume={77}, ISSN={["1094-1622"]}, DOI={10.1103/physreva.77.053408}, abstractNote={We report a first study of the depolarization behavior of spin polarized $^{3}\text{H}\text{e}$ in a mixture of $^{3}\text{H}\text{e-}^{4}\text{H}\text{e}$ at a temperature below the $^{4}\text{H}\text{e}$ $\ensuremath{\lambda}$ point in a deuterated tetraphenyl butadiene-doped deuterated polystyrene (dTPB-dPS) coated acrylic cell. In our experiment the measured $^{3}\text{H}\text{e}$ relaxation time is due to the convolution of the $^{3}\text{H}\text{e}$ longitudinal relaxation time, ${T}_{1}$, and the diffusion time constant of $^{3}\text{H}\text{e}$ in superfluid $^{4}\text{H}\text{e}$ since depolarization takes place on the walls. We have obtained a $^{3}\text{H}\text{e}$ relaxation time of $\ensuremath{\sim}3000\text{ }\text{s}$ at a temperature around 1.9 K. We have shown that it is possible to achieve values of wall depolarization probability on the order of $(1--2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ for polarized $^{3}\text{H}\text{e}$ in the superfluid $^{4}\text{H}\text{e}$ from a dTPB-dPS coated acrylic surface.}, number={5}, journal={PHYSICAL REVIEW A}, author={Ye, Q. and Dutta, D. and Gao, H. and Kramer, K. and Qian, X. and Zong, X. and Hannelius, L. and McKeown, R. D. and Heyburn, B. and Singer, S. and et al.}, year={2008}, month={May} }