Author
J. Billowes
Other affiliations: University of Göttingen
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 25, co-authored 185 publications receiving 2336 citations. Previous affiliations of J. Billowes include University of Göttingen.
Topics: Neutron, Spectroscopy, Fission, Hyperfine structure, Physics
Papers published on a yearly basis
Papers
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TL;DR: In collinear laser measurements the signal-to-noise ratio has been improved by a factor of 2 x 10(4), allowing spectroscopic measurements to be made with ion-beam fluxes of approximately 50 ions s(-1).
Abstract: A new method has been developed for increasing the sensitivity of collinear laser spectroscopy. The method utilizes an ion-trapping technique in which a continuous low-energy ion beam is cooled and accumulated in a linear Paul trap and subsequently released as a short ( $10--20\ensuremath{\mu}\mathrm{s}$) bunch. In collinear laser measurements the signal-to-noise ratio has been improved by a factor of $2\ifmmode\times\else\texttimes\fi{}{10}^{4}$, allowing spectroscopic measurements to be made with ion-beam fluxes of $\ensuremath{\sim}50\mathrm{ions}{\mathrm{s}}^{\ensuremath{-}1}$. The bunching method has been demonstrated in an on-line isotope shift and hyperfine structure measurement on radioactive ${}^{175}\mathrm{Hf}$.
130 citations
TL;DR: The first on-line laser spectroscopy of cooled fission fragments is reported, and the mean-square charge radii are found to be almost identical to those of the Sr isotones and previously offered modeling of the radial changes is critically reviewed.
Abstract: The first on-line laser spectroscopy of cooled fission fragments is reported. The $^{\mathrm{96}\mathrm{--}\mathrm{102}}\mathrm{Z}\mathrm{r}$ ions, produced in uranium fission, were extracted and separated using an ion guide isotope separator. The ions were cooled and bunched for collinear laser spectroscopy by a gas-filled linear Paul trap. New results for nuclear mean-square charge radii, dipole, and quadrupole moments are reported across the $N=60$ shape change. The mean-square charge radii are found to be almost identical to those of the Sr isotones and previously offered modeling of the radial changes is critically reviewed.
104 citations
Paul Scherrer Institute1, ENEA2, Karlsruhe Institute of Technology3, European Commission4, CERN5, Goethe University Frankfurt6, University of Łódź7, Université Paris-Saclay8, Vienna University of Technology9, University of Lisbon10, Charles University in Prague11, University of Manchester12, University of Zagreb13, University of Santiago de Compostela14, Polytechnic University of Catalonia15, University of Seville16, National Technical University of Athens17, University of Valencia18, Joint Institute for Nuclear Research19, Bhabha Atomic Research Centre20, Japan Atomic Energy Agency21, University of York22, Tokyo Institute of Technology23, University of Edinburgh24, University of Vienna25, German National Metrology Institute26, University of Ioannina27, University of Granada28, University of Basel29, Australian National University30
TL;DR: The energy-dependent cross section of the ^{7}Be(n,α)^{4}He reaction, of interest for the so-called cosmological lithium problem in big bang nucleosynthesis, has been measured for the first time from 10 meV to 10 keV neutron energy.
Abstract: The energy-dependent cross section of the (7)Bed(n,alpha)He-4 reaction, of interest for the so-called cosmological lithium problem in big bang nucleosynthesis, has been measured for the first time from 10 meV to 10 keV neutron energy. The challenges posed by the short half-life of Be-7 and by the low reaction cross section have been overcome at n_TOF thanks to an unprecedented combination of the extremely high luminosity and good resolution of the neutron beam in the new experimental area (EAR2) of the n_TOF facility at CERN, the availability of a sufficient amount of chemically pure Be-7, and a specifically designed experimental setup. Coincidences between the two alpha particles have been recorded in two Si-Be-7-Si arrays placed directly in the neutron beam. The present results are consistent, at thermal neutron energy, with the only previous measurement performed in the 1960s at a nuclear reactor. The energy dependence reported here clearly indicates the inadequacy of the cross section estimates currently used in BBN calculations. Although new measurements at higher neutron energy may still be needed, the n_TOF results hint at a minor role of this reaction in BBN, leaving the long-standing cosmological lithium problem unsolved.
99 citations
Katholieke Universiteit Leuven1, University of Manchester2, Max Planck Society3, CERN4, University of Birmingham5, University of Tübingen6, GSI Helmholtz Centre for Heavy Ion Research7, University of Mainz8, Petersburg Nuclear Physics Institute9, Royal Institute of Technology10, University of Oxford11, University of Tennessee12
TL;DR: In this article, the predicted inversion between the pi2p3/2 and pi1f5/2 nuclear states in the nu(g)9/2 midshell was confirmed by using a combination of in-source laser spectroscopy and collinear laser spectrometers on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments.
Abstract: We report the first confirmation of the predicted inversion between the pi2p3/2 and pi1f5/2 nuclear states in the nu(g)9/2 midshell. This was achieved at the ISOLDE facility, by using a combination of in-source laser spectroscopy and collinear laser spectroscopy on the ground states of 71,73,75Cu, which measured the nuclear spin and magnetic moments. The obtained values are mu(71Cu)=+2.2747(8)mu(N), mu(73Cu)=+1.7426(8)mu(N), and mu(75Cu)=+1.0062(13)mu(N) corresponding to spins I=3/2 for 71,73Cu and I=5/2 for 75Cu. The results are in fair agreement with large-scale shell-model calculations.
98 citations
TL;DR: Collinear laser spectroscopy was performed on Ga (Z=31) isotopes at ISOLDE, CERN to extend measurements towards very neutron-rich isotopes (N=36-50).
Abstract: Collinear laser spectroscopy was performed on Ga (Z=31) isotopes at ISOLDE, CERN. A gas-filled linear Paul trap (ISCOOL) was used to extend measurements towards very neutron-rich isotopes (N=36-50). A ground state (g.s.) spin I=1/2 is measured for 73Ga, being near degenerate with a 3/2{-} isomer (75 eV≲E{ex}≲1 keV). The 79Ga g.s., with I=3/2, is dominated by protons in the πf{5/2} orbital and in 81Ga the 5/2{-} level becomes the g.s. The data are compared to shell-model calculations in the f{5/2}pg{9/2} model space, calling for further theoretical developments and new experiments.
98 citations
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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
TL;DR: In this article, the root-mean-square (rms) nuclear charge radii R obtained by combined analysis of two types of experimental data: (i) radii changes determined from optical and, to a lesser extent, K α X-ray isotope shifts and (ii) absolute radii measured by muonic spectra and electronic scattering experiments.
1,172 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
01 Mar 2006-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
717 citations
TL;DR: The mass of the nucleus has been of capital importance not only for various aspects of nuclear physics, but also for other branches of physics, notably weak-interaction studies and astrophysics as mentioned in this paper.
Abstract: The mass of the nucleus, through its binding energy, continues to be of capital importance not only for various aspects of nuclear physics, but also for other branches of physics, notably weak-interaction studies and astrophysics. The authors first describe the modern experimental techniques dedicated to the particularly challenging task of measuring the mass of exotic nuclides and make detailed comparisons. Though tremendous progress in these and the associated production techniques has been made, allowing access to nuclides very far from stability, it is still not yet possible to produce many nuclides involved in stellar nucleosynthesis, especially the $r$ process, leaving no choice but to resort to theory. The review thus goes on to describe and critically compare the various modern mass formulas that may be used to extrapolate from the data towards the neutron drip line. Special attention is devoted to the crucial interplay between theory and experiment, showing how new measurements far from stability can considerably reduce the ambiguity in extrapolations to nuclides even further away.
555 citations