Author
J. Billowes
Other affiliations: University of Oxford, State University of New York System, Stony Brook University
Bio: J. Billowes is an academic researcher from University of Manchester. The author has contributed to research in topics: Neutron & Spectroscopy. The author has an hindex of 24, co-authored 117 publications receiving 1826 citations. Previous affiliations of J. Billowes include University of Oxford & State University of New York System.
Papers published on a yearly basis
Papers
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CERN1, National Technical University of Athens2, French Alternative Energies and Atomic Energy Commission3, Istituto Nazionale di Fisica Nucleare4, Vienna University of Technology5, Goethe University Frankfurt6, Centre national de la recherche scientifique7, Charles University in Prague8, University of Manchester9, University of Zagreb10, Polytechnic University of Catalonia11, Technical University of Lisbon12, University of Seville13, Spanish National Research Council14, University of Santiago de Compostela15, Paul Scherrer Institute16, Aristotle University of Thessaloniki17, Bhabha Atomic Research Centre18, University of York19, Karlsruhe Institute of Technology20, Oak Ridge National Laboratory21, University of Bologna22, ENEA23, University of Vienna24, University of Basel25
TL;DR: In this paper, the authors present the characteristics of the new neutron beam in the currently available configurations, which correspond to two different collimation systems and two choices of neutron moderator, including the intensity and energy dependence of the neutron flux, the spatial profile of the beam, the in-beam background components and the energy resolution/broadening.
Abstract: The neutron time-of-flight facility n_TOF features a white neutron source produced by spallation through 20GeV/c protons impinging on a lead target. The facility, aiming primarily at the measurement of neutron-induced reaction cross sections, was operating at CERN between 2001 and 2004, and then underwent a major upgrade in 2008. This paper presents in detail all the characteristics of the new neutron beam in the currently available configurations, which correspond to two different collimation systems and two choices of neutron moderator. The characteristics discussed include the intensity and energy dependence of the neutron flux, the spatial profile of the beam, the in-beam background components and the energy resolution/broadening. The discussion of these features is based on dedicated measurements and Monte Carlo simulations, and includes estimations of the systematic uncertainties of the mentioned quantities.
224 citations
Max Planck Society1, Heidelberg University2, Katholieke Universiteit Leuven3, CERN4, University of Liverpool5, University of Edinburgh6, University of the West of Scotland7, Sofia University8, Technische Universität Darmstadt9, Bulgarian Academy of Sciences10, Petersburg Nuclear Physics Institute11, University of Manchester12, Technische Universität München13, Spanish National Research Council14, Frankfurt Institute for Advanced Studies15, University of Surrey16, Lund University17, Australian National University18, University of Mainz19, Complutense University of Madrid20, University of Helsinki21, University of Jyväskylä22, Goethe University Frankfurt23, Ludwig Maximilian University of Munich24, Michigan State University25, Chinese Academy of Sciences26, University of York27, Chalmers University of Technology28, University of Groningen29, Daresbury Laboratory30, Beihang University31, University of Warsaw32, University of Cologne33, Aarhus University34, Columbia University35, Lawrence Livermore National Laboratory36, Stockholm University37, Weizmann Institute of Science38, University of Jena39, Helmholtz Institute Jena40, Saitama University41, Dresden University of Technology42
TL;DR: In this article, the authors proposed to install a storage ring at an ISOL-type radioactive beam facility for the first time, which can provide a capability for experiments with stored secondary beams that is unique in the world.
Abstract: We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report.
109 citations
CERN1, University of Manchester2, Katholieke Universiteit Leuven3, University of Tokyo4, Comenius University in Bratislava5, University of York6, Japan Atomic Energy Agency7, Max Planck Society8, Petersburg Nuclear Physics Institute9, University of the West of Scotland10, University of Paris-Sud11, University of Greifswald12, Dresden University of Technology13, University of Mainz14
TL;DR: In this article, the shape-staggering in the even-mass lead isotopes and odd-mass mercury isotopes was investigated and it was concluded that this phenomenon results from the interplay between monopole and quadrupole interactions driving a quantum phase transition.
Abstract: In rare cases, the removal of a single proton (Z) or neutron (N) from an atomic nucleus leads to a dramatic shape change. These instances are crucial for understanding the components of the nuclear interactions that drive deformation. The mercury isotopes (Z = 80) are a striking example1,2: their close neighbours, the lead isotopes (Z = 82), are spherical and steadily shrink with decreasing N. The even-mass (A = N + Z) mercury isotopes follow this trend. The odd-mass mercury isotopes 181,183,185Hg, however, exhibit noticeably larger charge radii. Due to the experimental difficulties of probing extremely neutron-deficient systems, and the computational complexity of modelling such heavy nuclides, the microscopic origin of this unique shape staggering has remained unclear. Here, by applying resonance ionization spectroscopy, mass spectrometry and nuclear spectroscopy as far as 177Hg, we determine 181Hg as the shape-staggering endpoint. By combining our experimental measurements with Monte Carlo shell model calculations, we conclude that this phenomenon results from the interplay between monopole and quadrupole interactions driving a quantum phase transition, for which we identify the participating orbitals. Although shape staggering in the mercury isotopes is a unique and localized feature in the nuclear chart, it nicely illustrates the concurrence of single-particle and collective degrees of freedom at play in atomic nuclei.
105 citations
CERN1, National Technical University of Athens2, University of Santiago de Compostela3, Goethe University Frankfurt4, Centre national de la recherche scientifique5, Charles University in Prague6, University of Manchester7, University of Zagreb8, Polytechnic University of Catalonia9, Technical University of Lisbon10, University of Seville11, Spanish National Research Council12, Paul Scherrer Institute13, Aristotle University of Thessaloniki14, Bhabha Atomic Research Centre15, Vienna University of Technology16, University of York17, Karlsruhe Institute of Technology18, Oak Ridge National Laboratory19, University of Vienna20, University of Bologna21, ENEA22, University of Basel23
TL;DR: In this article, the authors measured the neutron flux of the n_TOF facility at CERN, after installation of the new spallation target, with four different systems based on three neutron-converting reactions.
Abstract: The neutron flux of the n_TOF facility at CERN was measured, after installation of the new spallation target, with four different systems based on three neutron-converting reactions, which represent accepted cross sections standards in different energy regions. A careful comparison and combination of the different measurements allowed us to reach an unprecedented accuracy on the energy dependence of the neutron flux in the very wide range (thermal to 1 GeV) that characterizes the n_TOF neutron beam. This is a pre-requisite for the high accuracy of cross section measurements at n_TOF. An unexpected anomaly in the neutron-induced fission cross section of 235U is observed in the energy region between 10 and 30keV, hinting at a possible overestimation of this important cross section, well above currently assigned uncertainties.
86 citations
Katholieke Universiteit Leuven1, University of Liverpool2, Peking University3, Oak Ridge National Laboratory4, University of Tennessee5, Chalmers University of Technology6, University of Manchester7, Helsinki Institute of Physics8, University of Jyväskylä9, Centre national de la recherche scientifique10, Massachusetts Institute of Technology11, CERN12, Michigan State University13, Physical Research Laboratory14
TL;DR: In this article, the authors used the collinear resonance ionization spectroscopy method with β-decay detection to measure the charge radius of potassium isotopes up to 52K and showed no sign of magicity at 32 neutrons.
Abstract: Nuclear charge radii are sensitive probes of different aspects of the nucleon–nucleon interaction and the bulk properties of nuclear matter, providing a stringent test and challenge for nuclear theory. Experimental evidence suggested a new magic neutron number at N = 32 (refs. 1–3) in the calcium region, whereas the unexpectedly large increases in the charge radii4,5 open new questions about the evolution of nuclear size in neutron-rich systems. By combining the collinear resonance ionization spectroscopy method with β-decay detection, we were able to extend charge radii measurements of potassium isotopes beyond N = 32. Here we provide a charge radius measurement of 52K. It does not show a signature of magic behaviour at N = 32 in potassium. The results are interpreted with two state-of-the-art nuclear theories. The coupled cluster theory reproduces the odd–even variations in charge radii but not the notable increase beyond N = 28. This rise is well captured by Fayans nuclear density functional theory, which, however, overestimates the odd–even staggering effect in charge radii. These findings highlight our limited understanding of the nuclear size of neutron-rich systems, and expose problems that are present in some of the best current models of nuclear theory. The charge radii of potassium isotopes up to 52K are measured, and show no sign of magicity at 32 neutrons as previously suggested in calcium. The observations are interpreted with coupled cluster and density functional theory calculations.
79 citations
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28,685 citations
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TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These
9,929 citations
Brookhaven National Laboratory1, Los Alamos National Laboratory2, International Atomic Energy Agency3, Rensselaer Polytechnic Institute4, National Institute of Standards and Technology5, Oak Ridge National Laboratory6, Argonne National Laboratory7, Lawrence Livermore National Laboratory8, Lawrence Berkeley National Laboratory9, North Carolina State University10, University of Michigan11, Institut de radioprotection et de sûreté nucléaire12, TRIUMF13, Rosatom14, Chalk River Laboratories15, Paul Scherrer Institute16, Karlsruhe Institute of Technology17, University of Bucharest18, Joint Institute for Nuclear Research19
TL;DR: The new ENDF/B-VIII.0 evaluated nuclear reaction data library as mentioned in this paper includes improved thermal neutron scattering data and uses new evaluated data from the CIELO project for neutron reactions on 1 H, 16 O, 56 Fe, 235 U, 238 U and 239 Pu described in companion papers.
1,249 citations
01 Apr 2001
TL;DR: In this paper, the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even-even nuclides are given in Table I.
Abstract: Adopted values for the reduced electric quadrupole transition probability, B(E2)↑, from the ground state to the first-excited 2+ state of even–even nuclides are given in Table I. Values of τ, the mean life of the 2+ state; E, the energy; and β, the quadrupole deformation parameter, are also listed there. The ratio of β to the value expected from the single-particle model is presented. The intrinsic quadrupole moment, Q0, is deduced from the B(E2)↑ value. The product E×B(E2)↑ is expressed as a percentage of the energy-weighted total and isoscalar E2 sum-rule strengths.
Table II presents the data on which Table I is based, namely the experimental results for B(E2)↑ values with quoted uncertainties. Information is also given on the quantity measured and the method used. The literature has been covered to November 2000.
The adopted B(E2)↑ values are compared in Table III with the values given by systematics and by various theoretical models. Predictions of unmeasured B(E2)↑ values are also given in Table III.
955 citations
TL;DR: Lang as discussed by the authors reviewed Lang's work in the Journal of Scientific Instruments (JSI) and Supplement No 1, 1951 Pp xvi + 388 + iii + 80 (London: Institute of Physics, 1951).
Abstract: Journal of Scientific Instruments Editor: Dr H R Lang Vol 28 and Supplement No 1, 1951 Pp xvi + 388 + iii + 80 (London: Institute of Physics, 1951) Bound, £3 12s; unbound, £3
725 citations