@article{lavelle_leung_ito_2022, title={Comparison of MCNP thermal scattering laws to inelastic neutron scattering data}, volume={1027}, ISSN={["1872-9576"]}, url={http://dx.doi.org/10.1016/j.nima.2021.166255}, DOI={10.1016/j.nima.2021.166255}, abstractNote={Neutron transport computations employ thermal scattering laws (TSLs) to account for the influence of material structure and collective excitations at low energy (≲ 10 eV). Recent work has been undertaken to improve TSL accuracy and expand the number of available materials in the Evaluated Nuclear Data File (ENDF). However, comparison of TSL to measured data is often sparse. We present a method to evaluate TSL accuracy in the Monte Carlo N-Particle (MCNP) code by simulating inelastic neutron scattering (INS) measurement and comparing to data. The method is briefly described with example application to the recently released ENDF-VIII TSL library for polyethylene as well as a cryogenic PE TSL we are separately developing.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT}, publisher={Elsevier BV}, author={Lavelle, C. M. and Leung, K. K. H. and Ito, T. M.}, year={2022}, month={Mar} }
 @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{li_ahmed_banu_bartram_crowe_downie_emamian_feldman_gao_godagama_et al._2022, title={Proton Compton Scattering from Linearly Polarized Gamma Rays}, volume={128}, ISSN={["1079-7114"]}, url={http://dx.doi.org/10.1103/physrevlett.128.132502}, DOI={10.1103/physrevlett.128.132502}, abstractNote={Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives α_{E1}^{p}=13.8±1.2_{stat}±0.1_{BSR}±0.3_{theo},β_{M1}^{p}=0.2∓1.2_{stat}±0.1_{BSR}∓0.3_{theo} in units of 10^{-4} fm^{3}.}, number={13}, journal={PHYSICAL REVIEW LETTERS}, publisher={American Physical Society (APS)}, author={Li, X. and Ahmed, M. W. and Banu, A. and Bartram, C. and Crowe, B. and Downie, E. J. and Emamian, M. and Feldman, G. and Gao, H. and Godagama, D. and et al.}, year={2022}, month={Apr} }
 @article{compton scattering from 
he4
 at the tunl 
hiγs
 facility_2020, url={http://dx.doi.org/10.1103/physrevc.101.034618}, DOI={10.1103/physrevc.101.034618}, abstractNote={Differential cross sections for elastic Compton scattering from He4 have been measured with high statistical precision at the High Intensity γ-ray Source at laboratory scattering angles of 55∘, 90∘, and 125∘ using a quasi-monoenergetic photon beam with a weighted mean energy value of 81.3 MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from He4 to fully interpret the data.1 MoreReceived 9 December 2019Accepted 9 March 2020DOI:https://doi.org/10.1103/PhysRevC.101.034618©2020 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNuclear reactionsPhotonuclear reactionsPolarization phenomenaPropertiesA ≤ 5TechniquesCompton scatteringNuclear PhysicsAccelerators & Beams}, journal={Physical Review C}, year={2020}, month={Mar} }
 @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{leung_muhrer_hügle_ito_lutz_makela_morris_pattie_saunders_young_2019, title={A next-generation inverse-geometry spallation-driven ultracold neutron source}, volume={126}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.5109879}, DOI={10.1063/1.5109879}, abstractNote={The physics model of a next-generation spallation-driven high-current ultracold neutron (UCN) source capable of delivering an extracted UCN rate of around an-order-of-magnitude higher than the strongest proposed sources, and around three-orders-of-magnitude higher than existing sources, is presented. This UCN-current-optimized source would dramatically improve cutting-edge UCN measurements that are currently statistically limited. A novel "Inverse Geometry" design is used with 40 L of superfluid $^4$He (He-II), which acts as a converter of cold neutrons (CNs) to UCNs, cooled with state-of-the-art sub-cooled cryogenic technology to $\sim$1.6 K. Our design is optimized for a 100 W maximum heat load constraint on the He-II and its vessel. In our geometry, the spallation target is wrapped symmetrically around the UCN converter to permit raster scanning the proton beam over a relatively large volume of tungsten spallation target to reduce the demand on the cooling requirements, which makes it reasonable to assume that water edge-cooling only is sufficient. Our design is refined in several steps to reach $P_{UCN}=2.1\times10^9\,/$s under our other restriction of 1 MW maximum available proton beam power. We then study effects of the He-II scattering kernel as well as reductions in $P_{UCN}$ due to pressurization to reach $P_{UCN}=1.8\times10^9\,/$s. Finally, we provide a design for the UCN extraction system that takes into account the required He-II heat transport properties and implementation of a He-II containment foil that allows UCN transmission. We estimate a total useful UCN current from our source of $R_{use}=5\times10^8\,/$s from a 18 cm diameter guide 5 m from the source. Under a conservative "no return" approximation, this rate can produce an extracted density of $>1\times10^4\,/$cm$^3$ in $<$1000~L external experimental volumes with a $^{58}$Ni (335 neV) cut-off potential.}, number={22}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Leung, K. K. H. and Muhrer, G. and Hügle, T. and Ito, T. M. and Lutz, E. M. and Makela, M. and Morris, C. L. and Pattie, R. W., Jr. and Saunders, A. and Young, A. R.}, year={2019}, month={Dec}, pages={224901} }
 @article{leung_ahmed_alarcon_aleksandrova_baeßler_barrón-palos_bartoszek_beck_behzadipour_bessuille_et al._2019, title={The neutron electric dipole moment experiment at the Spallation Neutron Source}, volume={219}, url={http://dx.doi.org/10.1051/epjconf/201921902005}, DOI={10.1051/epjconf/201921902005}, abstractNote={Novel experimental techniques are required to make the next big leap in neutron electric dipole moment experimental sensitivity, both in terms of statistics and systematic error control. The nEDM experiment at the Spallation Neutron Source (nEDM@SNS) will implement the scheme of Golub & Lamoreaux [Phys. Rep., 237, 1 (1994)]. The unique properties of combining polarized ultracold neutrons, polarized 3 He, and superfluid 4 He will be exploited to provide a sensitivity to ∼ 10 −28 e · cm. Our cryogenic apparatus will deploy two small (3 L) measurement cells with a high density of ultracold neutrons produced and spin analyzed in situ. The electric field strength, precession time, magnetic shielding, and detected UCN number will all be enhanced compared to previous room temperature Ramsey measurements. Our 3 He co-magnetometer offers unique control of systematic effects, in particular the Bloch-Siegert induced false EDM. Furthermore, there will be two distinct measurement modes: free precession and dressed spin. This will provide an important self-check of our results. Following five years of “critical component demonstration,” our collaboration transitioned to a “large scale integration” phase in 2018. An overview of our measurement techniques, experimental design, and brief updates are described in these proceedings.}, journal={EPJ Web of Conferences}, author={Leung, K.K.H. and Ahmed, M. and Alarcon, R. and Aleksandrova, A. and Baeßler, S. and Barrón-Palos, L. and Bartoszek, L. and Beck, D.H. and Behzadipour, M. and Bessuille, J. and et al.}, year={2019}, pages={02005} }
 @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{steyerl_leung_kaufman_müller_malik_2017, title={Spin flip loss in magnetic confinement of ultracold neutrons for neutron lifetime experiments}, volume={95}, ISSN={2469-9985 2469-9993}, url={http://dx.doi.org/10.1103/PhysRevC.95.035502}, DOI={10.1103/physrevc.95.035502}, abstractNote={We analyze the spin flip loss for ultracold neutrons in magnetic bottles of the type used in experiments aiming at a precise measurement of the neutron lifetime, extending the one-dimensional field model used previously by Steyerl $\textit{et al.}$ [Phys.Rev.C $\mathbf{86}$, 065501 (2012)] to two dimensions for cylindrical multipole fields. We also develop a general analysis applicable to three dimensions. Here we apply it to multipole fields and to the bowl-type field configuration used for the Los Alamos UCN$\tau$ experiment. In all cases considered the spin flip loss calculated exceeds the Majorana estimate by many orders of magnitude but can be suppressed sufficiently by applying a holding field of appropriate magnitude to allow high-precision neutron lifetime measurements, provided other possible sources of systematic error are under control.}, number={3}, journal={Physical Review C}, publisher={American Physical Society (APS)}, author={Steyerl, A. and Leung, K. K. H. and Kaufman, C. and Müller, G. and Malik, S. S.}, year={2017}, month={Mar} }
 @article{leung_geltenbort_ivanov_rosenau_zimmer_2016, title={Neutron lifetime measurements and effective spectral cleaning with an ultracold neutron trap using a vertical Halbach octupole permanent magnet array}, volume={94}, ISSN={2469-9985 2469-9993}, url={http://dx.doi.org/10.1103/PhysRevC.94.045502}, DOI={10.1103/physrevc.94.045502}, abstractNote={Ultracold neutron (UCN) storage measurements were made in a trap constructed from a 1.3-T Halbach octupole permanent (HOPE) magnet array aligned vertically, using the TES port of the PF2 source at the Institut Laue-Langevin. A mechanical UCN valve at the bottom of the trap was used for filling and emptying. This valve was covered with Fomblin grease to induce nonspecular reflections and was used in combination with a movable polyethylene UCN remover inserted from the top for cleaning of above-threshold UCNs. Loss from UCN depolarization was suppressed with a minimum 2-mT bias field. Without using the UCN remover, a total storage time constant of $(712\ifmmode\pm\else\textpm\fi{}19)\phantom{\rule{4pt}{0ex}}\mathrm{s}$ was observed; with the remover inserted for 80 s and used at either 80 cm or 65 cm from the bottom of the trap, time constants of $(824\ifmmode\pm\else\textpm\fi{}32)\phantom{\rule{4pt}{0ex}}\mathrm{s}$ and $(835\ifmmode\pm\else\textpm\fi{}36)\phantom{\rule{4pt}{0ex}}\mathrm{s}$ were observed. Combining the latter two values, a neutron lifetime of ${\ensuremath{\tau}}_{\mathrm{n}}=(887\ifmmode\pm\else\textpm\fi{}39)\phantom{\rule{4pt}{0ex}}\mathrm{s}$ is extracted after primarily correcting for losses at the UCN valve. The time constants of the UCN population during cleaning were observed and compared to calculations based on kinetic theory as well as Monte Carlo studies. These calculations are used to predict above-threshold populations of $\ensuremath{\sim}5%,\phantom{\rule{0.16em}{0ex}}\ensuremath{\sim}0.5%$, and $\ensuremath{\sim}{10}^{\ensuremath{-}12}%$ remaining after cleaning in the no-remover, 80-cm remover, and 65-cm remover measurements. Thus, by using a nonspecular reflector covering the entire bottom of the trap and a remover at the top of the trap, we have established an effective cleaning procedure for removing a major systematic effect in high-precision ${\ensuremath{\tau}}_{\mathrm{n}}$ experiments with magnetically stored UCNs.}, number={4}, journal={Physical Review C}, publisher={American Physical Society (APS)}, author={Leung, K. K. H. and Geltenbort, P. and Ivanov, S. and Rosenau, F. and Zimmer, O.}, year={2016}, month={Oct} }
 @article{wei_broussard_hoffbauer_makela_morris_tang_adamek_callahan_clayton_cude-woods_et al._2016, title={Position-sensitive detection of ultracold neutrons with an imaging camera and its implications to spectroscopy}, volume={830}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/j.nima.2016.05.058}, DOI={10.1016/j.nima.2016.05.058}, abstractNote={Position-sensitive detection of ultracold neutrons (UCNs) is demonstrated using an imaging charge-coupled device (CCD) camera. A spatial resolution less than 15μm has been achieved, which is equivalent to a UCN energy resolution below 2 pico-electron-volts through the relation δE=m0gδx. Here, the symbols δE, δx, m0 and g are the energy resolution, the spatial resolution, the neutron rest mass and the gravitational acceleration, respectively. A multilayer surface convertor described previously is used to capture UCNs and then emits visible light for CCD imaging. Particle identification and noise rejection are discussed through the use of light intensity profile analysis. This method allows different types of UCN spectroscopy and other applications.}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Wei, Wanchun and Broussard, L.J. and Hoffbauer, M.A. and Makela, M. and Morris, C.L. and Tang, Z. and Adamek, E.R. and Callahan, N.B. and Clayton, S.M. and Cude-Woods, C. and et al.}, year={2016}, month={Sep}, pages={36–43} }
 @article{leung_ivanov_piegsa_simson_zimmer_2016, title={Ultracold-neutron production and up-scattering in superfluid helium between 1.1 K and 2.4 K}, volume={93}, ISSN={2469-9985 2469-9993}, url={http://dx.doi.org/10.1103/PhysRevC.93.025501}, DOI={10.1103/physrevc.93.025501}, abstractNote={Ultracold neutrons (UCNs) were produced in a 4 liter volume of superfluid helium using the PF1B cold neutron beam facility at the Institut Laue-Langevin and then extracted to a detector at room temperature. With a converter temperature of 1.08 K the number of accumulated UCNs was counted to be $91,\!700 \pm 300$. From this, we derive a volumetric UCN production rate of $(6.9 \pm 1.7)\,\mathrm{cm^{-3}\,s^{-1}}$, which includes a correction for losses in the converter during UCN extraction caused by a short storage time, but not accounting for UCN transport and detection efficiencies. The up-scattering rate of UCNs due to excitations in the superfluid was studied by scanning the temperature between 1.2-2.4 K. Using the temperature-dependent UCN production rate calculated from inelastic neutron scattering data in the analysis, the only UCN up-scattering process found to be present was from two-phonon scattering. Our analysis rules out contributions from the other scattering processes to $\lesssim 10\%$ of their predicted levels.}, number={2}, journal={Physical Review C}, publisher={American Physical Society (APS)}, author={Leung, K. K. H. and Ivanov, S. and Piegsa, F. M. and Simson, M. and Zimmer, O.}, year={2016}, month={Feb} }
 @article{schmidt-wellenburg_bossy_farhi_fertl_leung_rahli_soldner_zimmer_2015, title={Experimental study of ultracold neutron production in pressurized superfluid helium}, volume={92}, ISSN={0556-2813 1089-490X}, url={http://dx.doi.org/10.1103/PhysRevC.92.024004}, DOI={10.1103/physrevc.92.024004}, abstractNote={We have investigated experimentally the pressure dependence of the production of ultracold neutrons (UCN) in superfluid helium in the range from saturated vapor pressure to 20bar. A neutron velocity selector allowed the separation of underlying single-phonon and multiphonon pro- cesses by varying the incident cold neutron (CN) wavelength in the range from 3.5 to 10{\AA}. The predicted pressure dependence of UCN production derived from inelastic neutron scattering data was confirmed for the single-phonon excitation. For multiphonon based UCN production we found no significant dependence on pressure whereas calculations from inelastic neutron scattering data predict an increase of 43(6)% at 20bar relative to saturated vapor pressure. From our data we conclude that applying pressure to superfluid helium does not increase the overall UCN production rate at a typical CN guide.}, number={2}, journal={Physical Review C}, publisher={American Physical Society (APS)}, author={Schmidt-Wellenburg, P. and Bossy, J. and Farhi, E. and Fertl, M. and Leung, K. K. H. and Rahli, A. and Soldner, T. and Zimmer, O.}, year={2015}, month={Aug} }
 @inproceedings{leung_ivanov_martin_rosenau_simson_zimmer_2014, title={A Comparison of Two Magnetic Ultra-Cold Neutron Trapping Concepts Using a Halbach-Octupole Array}, ISBN={9789814571661 9789814571678}, url={http://dx.doi.org/10.1142/9789814571678_0015}, DOI={10.1142/9789814571678_0015}, abstractNote={This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2 m long Halbach-octupole array of permanent magnets with an inner bore radius of 47 mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.}, booktitle={Next Generation Experiments to Measure the Neutron Lifetime}, publisher={WORLD SCIENTIFIC}, author={Leung, K. and Ivanov, S. and Martin, F. and Rosenau, F. and Simson, M. and Zimmer, O.}, year={2014}, month={Mar} }
 @article{piegsa_fertl_ivanov_kreuz_leung_schmidt-wellenburg_soldner_zimmer_2014, title={New source for ultracold neutrons at the Institut Laue-Langevin}, volume={90}, ISSN={0556-2813 1089-490X}, url={http://dx.doi.org/10.1103/PhysRevC.90.015501}, DOI={10.1103/physrevc.90.015501}, abstractNote={A new intense superthermal source for ultracold neutrons (UCN) has been installed at a dedicated beam line at the Institut Laue-Langevin. Incident neutrons with a wavelength of 0.89 nm are converted to UCN in a five liter volume filled with superfluid $^4$He at a temperature of about 0.7 K. The UCN can be extracted to room temperature experiments. We present the cryogenic setup of the source, a characterization of the cold neutron beam, and UCN production measurements, where a UCN density in the production volume of at least 55 per cm$^3$ was determined.}, number={1}, journal={Physical Review C}, publisher={American Physical Society (APS)}, author={Piegsa, F. M. and Fertl, M. and Ivanov, S. N. and Kreuz, M. and Leung, K. K. H. and Schmidt-Wellenburg, P. and Soldner, T. and Zimmer, O.}, year={2014}, month={Jul} }
 @phdthesis{leung_2013, title={Development of a new superfluid helium ultra-cold neutron source and a new magnetic trap for neutron lifetime measurements}, url={http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:91-diss-20130213-1119646-0-0}, school={Technische Universität München.}, author={Leung, Kent}, year={2013} }
 @article{barker_leung_byrne_2009, title={Half-life of the superallowed positron emitter Carbon-10}, volume={79}, ISSN={0556-2813 1089-490X}, url={http://dx.doi.org/10.1103/PhysRevC.79.024311}, DOI={10.1103/physrevc.79.024311}, abstractNote={The half-life of the nucleus $^{10}\mathrm{C}$ has been determined by detecting its decay positrons in an $E\ensuremath{-}\ensuremath{\Delta}E$ fast scintillator telescope and recording the data in event mode. Care was taken to exclude the effects of possible contaminant activities and of pileup in the linear electronic systems. A value of 19.282(11) s has been obtained, which is in good agreement with two of the three previous measurements, but not with the most recent.}, number={2}, journal={Physical Review C}, publisher={American Physical Society (APS)}, author={Barker, P. H. and Leung, K. K. H. and Byrne, A. P.}, year={2009}, month={Feb}, pages={024311} }
 @article{simson_ayala guardia_baeßler_borg_glück_heil_konorov_konrad_muñoz horta_leung_et al._2009, title={Measuring the proton spectrum in neutron decay—Latest results with aSPECT}, volume={611}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/j.nima.2009.07.068}, DOI={10.1016/j.nima.2009.07.068}, abstractNote={The retardation spectrometer aSPECT was built to measure the shape of the proton spectrum in free neutron decay with high precision. This allows us to determine the antineutrino electron angular correlation coefficient a. We aim for a precision more than one order of magnitude better than the present best value, which is Delta_a /a = 5%. In a recent beam time performed at the Institut Laue-Langevin during April / May 2008 we reached a statistical accuracy of about 2% per 24 hours measurement time. Several systematic effects were investigated experimentally. We expect the total relative uncertainty to be well below 5%.}, number={2-3}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Simson, M. and Ayala Guardia, F. and Baeßler, S. and Borg, M. and Glück, F. and Heil, W. and Konorov, I. and Konrad, G. and Muñoz Horta, R. and Leung, K.K.H. and et al.}, year={2009}, month={Dec}, pages={203–206} }
 @article{leung_zimmer_2009, title={Proposed neutron lifetime measurement using a hybrid magnetic trap for ultra-cold neutrons}, volume={611}, ISSN={0168-9002}, url={http://dx.doi.org/10.1016/j.nima.2009.07.087}, DOI={10.1016/j.nima.2009.07.087}, abstractNote={Current values of the neutron β-decay lifetime have come under scrutiny due to a large disagreement between recent precise measurements using trapping of ultra-cold neutrons (UCNs) in material bottles. These measurements involve extrapolation procedures to correct the observed storage times for neutron losses due to interactions with material walls. Magnetic trapping of UCNs avoids neutron–matter interactions and thus offers an alternative technique with different systematics. We present our plans toward a new neutron lifetime measurement using a hybrid Ioffe-type trap made with a Halbach-type permanent octupole magnet combined with superconducting coils. The proposed experimental procedure extracts into vacuum UCNs produced from a superfluid helium converter through a moving thin foil and detects the neutron decays via live extraction of produced protons.}, number={2-3}, journal={Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment}, publisher={Elsevier BV}, author={Leung, K.K.H. and Zimmer, O.}, year={2009}, month={Dec}, pages={181–185} }
 @article{konrad_ayala guardia_baeßler_borg_glück_heil_konorov_leung_muñoz horta_simson_et al._2009, title={The Proton Spectrum in Neutron Beta Decay: Latest Results with the aSPECT Spectrometer}, volume={827}, ISSN={0375-9474}, url={http://dx.doi.org/10.1016/j.nuclphysa.2009.05.114}, DOI={10.1016/j.nuclphysa.2009.05.114}, abstractNote={Abstract The purpose of the neutron decay spectrometer aSPECT is to determine the antineutrino electron angular correlation coefficient a with high precision. Latest measurements with aSPECT were performed during April/May 2008 at the Institut Laue-Langevin in Grenoble, France. In this paper we give a report on the experiment and the status of the ongoing data analysis.}, number={1-4}, journal={Nuclear Physics A}, publisher={Elsevier BV}, author={Konrad, G. and Ayala Guardia, F. and Baeßler, S. and Borg, M. and Glück, F. and Heil, W. and Konorov, I. and Leung, K.K.H. and Muñoz Horta, R. and Simson, M. and et al.}, year={2009}, month={Aug}, pages={529c–531c} }